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Search for a dark Higgs boson produced in association with inelastic dark matter at the Belle II experiment
Authors:
Belle II Collaboration,
I. Adachi,
L. Aggarwal,
H. Ahmed,
H. Aihara,
N. Akopov,
S. Alghamdi,
M. Alhakami,
A. Aloisio,
N. Althubiti,
K. Amos,
M. Angelsmark,
N. Anh Ky,
C. Antonioli,
D. M. Asner,
H. Atmacan,
V. Aushev,
M. Aversano,
R. Ayad,
V. Babu,
N. K. Baghel,
S. Bahinipati,
P. Bambade,
Sw. Banerjee,
S. Bansal
, et al. (415 additional authors not shown)
Abstract:
Inelastic dark matter models that have two dark matter particles and a massive dark photon can reproduce the observed relic dark matter density without violating cosmological limits. The mass splitting between the two dark matter particles χ_{1} and χ_{2}, with m(χ_{2}) > m(χ_{1}), is induced by a dark Higgs field and a corresponding dark Higgs boson h^{\prime}. We present a search for dar…
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Inelastic dark matter models that have two dark matter particles and a massive dark photon can reproduce the observed relic dark matter density without violating cosmological limits. The mass splitting between the two dark matter particles χ_{1} and χ_{2}, with m(χ_{2}) > m(χ_{1}), is induced by a dark Higgs field and a corresponding dark Higgs boson h^{\prime}. We present a search for dark matter in events with two vertices, at least one of which must be displaced from the interaction region, and missing energy. Using a 365\,\mbox{fb}^{-1} data sample collected at Belle II, which operates at the SuperKEKB e^+e^- collider, we observe no evidence for a signal. We set upper limits on the product of the production cross section σ\left(e^+e^- \to h^\prime χ_1 χ_2\right), and the product of branching fractions \mathcal{B}\left(χ_2\toχ_1 e^+ e^-\right)\times\mathcal{B}\left(h^\prime\to x^+x^-\right), where x^+x^- indicates μ^+μ^-, π^+π^-, or K^+K^-, as functions of h^{\prime} mass and lifetime at the level of 10^{-1}\,\mbox{fb}. We set model-dependent upper limits on the dark Higgs mixing angle at the level of 10^{-5} and on the dark photon kinetic mixing parameter at the level of 10^{-3}. This is the first search for dark Higgs bosons in association with inelastic dark matter.
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Submitted 14 May, 2025;
originally announced May 2025.
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Search for lepton flavor-violating decay modes B^0 \to K^{\ast 0}τ^\pm\ell^\mp (\ell = e,μ) with hadronic B-tagging at Belle and Belle II
Authors:
Belle,
Belle II Collaborations,
:,
I. Adachi,
Y. Ahn,
H. Aihara,
N. Akopov,
S. Alghamdi,
M. Alhakami,
A. Aloisio,
K. Amos,
M. Angelsmark,
N. Anh Ky,
C. Antonioli,
D. M. Asner,
H. Atmacan,
V. Aushev,
M. Aversano,
R. Ayad,
V. Babu,
H. Bae,
N. K. Baghel,
S. Bahinipati,
P. Bambade,
Sw. Banerjee
, et al. (353 additional authors not shown)
Abstract:
We present the results of a search for the charged-lepton-flavor violating decays B^0 \rightarrow K^{*0}τ^\pm \ell^{\mp}, where \ell^{\mp} is either an electron or a muon. The results are based on 365 fb^{-1} and 711 fb^{-1} datasets collected with the Belle II and Belle detectors, respectively. We use an exclusive hadronic B-tagging technique, and search for a signal decay in the system…
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We present the results of a search for the charged-lepton-flavor violating decays B^0 \rightarrow K^{*0}τ^\pm \ell^{\mp}, where \ell^{\mp} is either an electron or a muon. The results are based on 365 fb^{-1} and 711 fb^{-1} datasets collected with the Belle II and Belle detectors, respectively. We use an exclusive hadronic B-tagging technique, and search for a signal decay in the system recoiling against a fully reconstructed B meson. We find no evidence for B^0 \rightarrow K^{*0}τ^\pm \ell^{\mp} decays and set upper limits on the branching fractions in the range of (2.9-6.4)\times10^{-5} at 90% confidence level.
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Submitted 13 May, 2025;
originally announced May 2025.
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Measurement of the time-integrated CP asymmetry in D^0\toπ^0π^0 decays at Belle II
Authors:
Belle II Collaboration,
I. Adachi,
Y. Ahn,
N. Akopov,
S. Alghamdi,
M. Alhakami,
A. Aloisio,
N. Althubiti,
K. Amos,
M. Angelsmark,
N. Anh Ky,
C. Antonioli,
D. M. Asner,
H. Atmacan,
T. Aushev,
M. Aversano,
R. Ayad,
V. Babu,
H. Bae,
N. K. Baghel,
S. Bahinipati,
P. Bambade,
Sw. Banerjee,
M. Barrett,
M. Bartl
, et al. (350 additional authors not shown)
Abstract:
We measure the time-integrated CP asymmetry, A_{CP}, in D^0\toπ^0π^0 decays reconstructed in e^+e^-\to c\bar{c} events collected by Belle II during 2019--2022. The data corresponds to an integrated luminosity of 428\mathrm{fb}^{-1}. The D^0 decays are required to originate from the flavor-conserving D^{*+} \to D^0 π^+ decay to determine the charm flavor at production time. Control sa…
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We measure the time-integrated CP asymmetry, A_{CP}, in D^0\toπ^0π^0 decays reconstructed in e^+e^-\to c\bar{c} events collected by Belle II during 2019--2022. The data corresponds to an integrated luminosity of 428\mathrm{fb}^{-1}. The D^0 decays are required to originate from the flavor-conserving D^{*+} \to D^0 π^+ decay to determine the charm flavor at production time. Control samples of D^0\to K^- π^+ decays, with or without an associated pion from a D^{*+} decay, are used to correct for detection asymmetries. The result, A_{CP}(D^0\toπ^0π^0) = (0.30\pm 0.72\pm 0.20)\%, where the first uncertainty is statistical and the second systematic, is consistent with CP symmetry.
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Submitted 5 May, 2025;
originally announced May 2025.
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Measurement of the time-integrated CP asymmetry in D^0 \to K^0_{\rm S} K^0_{\rm S} decays using opposite-side flavor tagging at Belle and Belle II
Authors:
Belle,
Belle II Collaborations,
:,
I. Adachi,
Y. Ahn,
N. Akopov,
S. Alghamdi,
M. Alhakami,
A. Aloisio,
N. Althubiti,
K. Amos,
M. Angelsmark,
N. Anh Ky,
C. Antonioli,
D. M. Asner,
H. Atmacan,
T. Aushev,
M. Aversano,
R. Ayad,
V. Babu,
H. Bae,
N. K. Baghel,
S. Bahinipati,
P. Bambade,
Sw. Banerjee
, et al. (356 additional authors not shown)
Abstract:
We measure the time-integrated CP asymmetry in D^0 \to K^0_{\rm S} K^0_{\rm S} decays reconstructed in e^+e^-\to c{\overline c} events collected by the Belle and Belle II experiments. The corresponding data samples have integrated luminosities of 980 and 428 fb{}^{-1}, respectively. To infer the flavor of the D^0 meson, we exploit the correlation between the flavor of the reconstructed d…
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We measure the time-integrated CP asymmetry in D^0 \to K^0_{\rm S} K^0_{\rm S} decays reconstructed in e^+e^-\to c{\overline c} events collected by the Belle and Belle II experiments. The corresponding data samples have integrated luminosities of 980 and 428 fb{}^{-1}, respectively. To infer the flavor of the D^0 meson, we exploit the correlation between the flavor of the reconstructed decay and the electric charges of particles reconstructed in the rest of the e^+e^-\to c{\overline c} event. This results in a sample which is independent from any other previously used at Belle or Belle II. The result, A_{CP}(D^0 \to K^0_{\rm S} K^0_{\rm S}) = (1.3 \pm 2.0 \pm 0.2)\%, where the first uncertainty is statistical and the second systematic, is consistent with previous determinations and with CP symmetry.
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Submitted 22 April, 2025;
originally announced April 2025.
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Search for lepton-flavor-violating τ^- \to \ell^- K_s^0 decays at Belle and Belle II
Authors:
Belle,
Belle II Collaborations,
:,
I. Adachi,
L. Aggarwal,
H. Ahmed,
Y. Ahn,
H. Aihara,
N. Akopov,
S. Alghamdi,
M. Alhakami,
A. Aloisio,
N. Althubiti,
K. Amos,
M. Angelsmark,
N. Anh Ky,
C. Antonioli,
D. M. Asner,
H. Atmacan,
V. Aushev,
M. Aversano,
R. Ayad,
V. Babu,
N. K. Baghel,
S. Bahinipati
, et al. (397 additional authors not shown)
Abstract:
We present the results of a search for charged-lepton-flavor violating decays τ^{-} \rightarrow \ell^{-}K_{S}^{0}, where \ell^{-} is either an electron or a muon. We combine e^+e^- data samples recorded by the Belle II experiment at the SuperKEKB collider (428 fb^{-1}) with samples recorded by the Belle experiment at the KEKB collider (980 fb^{-1}) to obtain a sample of 1.3 billion…
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We present the results of a search for charged-lepton-flavor violating decays τ^{-} \rightarrow \ell^{-}K_{S}^{0}, where \ell^{-} is either an electron or a muon. We combine e^+e^- data samples recorded by the Belle II experiment at the SuperKEKB collider (428 fb^{-1}) with samples recorded by the Belle experiment at the KEKB collider (980 fb^{-1}) to obtain a sample of 1.3 billion e^+e^-\toτ^+τ^- events. We observe 0 and 1 events and set 90\% confidence level upper limits of 0.8 \times 10^{-8} and 1.2 \times 10^{-8} on the branching fractions of the decay modes τ^{-} \rightarrow e^{-}K_{S}^{0} and τ^{-} \rightarrow μ^{-}K_{S}^{0}, respectively. These are the most stringent upper limits to date.
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Submitted 22 April, 2025;
originally announced April 2025.
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Test of lepton flavor universality with measurements of R(D^{+}) and R(D^{*+}) using semileptonic B tagging at the Belle II experiment
Authors:
Belle II Collaboration,
I. Adachi,
K. Adamczyk,
L. Aggarwal,
H. Ahmed,
H. Aihara,
N. Akopov,
S. Alghamdi,
M. Alhakami,
A. Aloisio,
N. Althubiti,
K. Amos,
M. Angelsmark,
N. Anh Ky,
C. Antonioli,
D. M. Asner,
H. Atmacan,
T. Aushev,
V. Aushev,
M. Aversano,
R. Ayad,
V. Babu,
H. Bae,
N. K. Baghel,
S. Bahinipati
, et al. (428 additional authors not shown)
Abstract:
We report measurements of the ratios of branching fractions \mathcal{R}(D^{(*)+}) = \mathcal{B}(\overline{B}{}^0 \to D^{(*)+} \,τ^- \, \overlineν_τ) / \mathcal{B}(\overline{B}{}^0 \to D^{(*)+} \, \ell^- \, \overlineν_\ell), where \ell denotes either an electron or a muon. These ratios test the universality of the charged-current weak interaction. The results are based on a…
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We report measurements of the ratios of branching fractions \mathcal{R}(D^{(*)+}) = \mathcal{B}(\overline{B}{}^0 \to D^{(*)+} \,τ^- \, \overlineν_τ) / \mathcal{B}(\overline{B}{}^0 \to D^{(*)+} \, \ell^- \, \overlineν_\ell), where \ell denotes either an electron or a muon. These ratios test the universality of the charged-current weak interaction. The results are based on a 365\, \mathrm{fb}^{-1} data sample collected with the Belle II detector at the SuperKEKB e^+e^- collider, which operates at a center-of-mass energy corresponding to the Υ(4S) resonance, just above the threshold for B\overline{B}{} production. Signal candidates are reconstructed by selecting events in which the companion B meson from the Υ(4S) \to B\overline{B}{} decay is identified in semileptonic modes. The τ lepton is reconstructed via its leptonic decays. We obtain \mathcal{R}(D^+) = 0.418 \pm 0.074 ~({\mathrm{stat}}) \pm 0.051 ~({\mathrm{syst}}) and \mathcal{R}(D^{*+}) = 0.306 \pm 0.034 ~({\mathrm{stat}}) \pm 0.018 ~({\mathrm{syst}}), which are consistent with world average values. Accounting for the correlation between them, these values differ from the Standard Model expectation by a collective significance of 1.7 standard deviations.
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Submitted 15 April, 2025;
originally announced April 2025.
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Search for B^0 \to K^{\ast 0} τ^+ τ^- decays at the Belle II experiment
Authors:
Belle II Collaboration,
I. Adachi,
K. Adamczyk,
L. Aggarwal,
H. Ahmed,
H. Aihara,
N. Akopov,
M. Alhakami,
A. Aloisio,
N. Althubiti,
M. Angelsmark,
N. Anh Ky,
D. M. Asner,
H. Atmacan,
V. Aushev,
M. Aversano,
R. Ayad,
V. Babu,
H. Bae,
N. K. Baghel,
S. Bahinipati,
P. Bambade,
Sw. Banerjee,
S. Bansal,
M. Barrett
, et al. (424 additional authors not shown)
Abstract:
We present a search for the rare flavor-changing neutral-current decay B^0 \to K^{\ast 0} τ^+ τ^- with data collected by the Belle II experiment at the SuperKEKB electron-positron collider. The analysis uses a 365 fb^{-1} data sample recorded at the center-of-mass energy of the Υ(4S) resonance. One of the B mesons produced in the Υ(4S)\to B^0 \bar{B}^0 process is fully reconstructed in a…
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We present a search for the rare flavor-changing neutral-current decay B^0 \to K^{\ast 0} τ^+ τ^- with data collected by the Belle II experiment at the SuperKEKB electron-positron collider. The analysis uses a 365 fb^{-1} data sample recorded at the center-of-mass energy of the Υ(4S) resonance. One of the B mesons produced in the Υ(4S)\to B^0 \bar{B}^0 process is fully reconstructed in a hadronic decay mode, while its companion B meson is required to decay into a K^{\ast 0} and two τ leptons of opposite charge. The τ leptons are reconstructed in final states with a single electron, muon, charged pion or charged ρ meson, and additional neutrinos. We set an upper limit on the branching ratio of BR(B^0 \to K^{\ast 0} τ^+ τ^-) < 1.8 \times 10^{-3} at the 90% confidence level, which is the most stringent constraint reported to date.
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Submitted 14 April, 2025;
originally announced April 2025.
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Search for lepton-flavor-violating tau decays to \ellα at Belle
Authors:
Belle Collaboration,
K. Uno,
K. Inami,
K. Hayasaka,
H. Aihara,
R. Ayad,
Sw. Banerjee,
K. Belous,
J. Bennett,
M. Bessner,
D. Biswas,
D. Bodrov,
M. Bračko,
P. Branchini,
T. E. Browder,
A. Budano,
M. Campajola,
K. Cho,
S. -K. Choi,
Y. Choi,
S. Choudhury,
G. De Nardo,
G. De Pietro,
F. Di Capua,
J. Dingfelder
, et al. (99 additional authors not shown)
Abstract:
We report a search for the lepton-flavor-violating decays τ^{\pm}\to\ell^{\pm}α~(\ell=e,μ), where α is an undetected spin-0 particle, such as an axion-like particle using 736\times10^{6} tau lepton pairs collected by the Belle detector at the KEKB asymmetric-energy e^{+}e^{-} collider. We find no evidence of signal and obtain the most stringent upper limits on the branching fractions at…
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We report a search for the lepton-flavor-violating decays τ^{\pm}\to\ell^{\pm}α~(\ell=e,μ), where α is an undetected spin-0 particle, such as an axion-like particle using 736\times10^{6} tau lepton pairs collected by the Belle detector at the KEKB asymmetric-energy e^{+}e^{-} collider. We find no evidence of signal and obtain the most stringent upper limits on the branching fractions at 95\% confidence level: \mathcal{B}_{95}(τ^{\pm}\rightarrow e^{\pm}α) < (0.4--6.4)\times10^{-4} and \mathcal{B}_{95}(τ^{\pm}\rightarrow μ^{\pm}α) < (0.2--3.5)\times10^{-4} for an α mass in the range 0.0\leq m_α\leq 1.6~GeV/c^{2}.
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Submitted 28 March, 2025;
originally announced March 2025.
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Measurements of the branching fractions of Ξ_{c}^{+}\to Σ^{+}K_{S}^{0}, Ξ_{c}^{+}\to Ξ^{0}π^{+}, and Ξ_{c}^{+}\to Ξ^{0}K^{+} at Belle and Belle II
Authors:
Belle,
Belle II Collaborations,
:,
I. Adachi,
J. K. Ahn,
Y. Ahn,
N. Akopov,
S. Alghamdi,
M. Alhakami,
N. Althubiti,
K. Amos,
N. Anh Ky,
C. Antonioli,
D. M. Asner,
M. Aversano,
R. Ayad,
V. Babu,
N. K. Baghel,
P. Bambade,
Sw. Banerjee,
M. Barrett,
M. Bartl,
J. Baudot,
A. Beaubien,
F. Becherer
, et al. (335 additional authors not shown)
Abstract:
Using 983.0 \rm{fb}^{-1} and 427.9 \rm{fb}^{-1} data samples collected with the Belle and Belle II detectors at the KEKB and SuperKEKB asymmetric energy e^+e^- colliders, respectively, we present studies of the Cabibbo-favored Ξ_c^+ decays {Ξ_{c}^{+}\to Σ^{+}K_{S}^{0}} and Ξ_{c}^{+}\to Ξ^{0}π^{+}, and the singly Cabibbo-suppressed decay Ξ_{c}^{+}\to Ξ^{0}K^{+}. The ratios of branchin…
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Using 983.0 \rm{fb}^{-1} and 427.9 \rm{fb}^{-1} data samples collected with the Belle and Belle II detectors at the KEKB and SuperKEKB asymmetric energy e^+e^- colliders, respectively, we present studies of the Cabibbo-favored Ξ_c^+ decays {Ξ_{c}^{+}\to Σ^{+}K_{S}^{0}} and Ξ_{c}^{+}\to Ξ^{0}π^{+}, and the singly Cabibbo-suppressed decay Ξ_{c}^{+}\to Ξ^{0}K^{+}. The ratios of branching fractions of {Ξ_{c}^{+}\to Σ^{+}K_{S}^{0}} and Ξ_{c}^{+}\to Ξ^{0}K^{+} relative to that of Ξ_{c}^{+}\toΞ^{-}π^{+}π^{+} are measured for the first time, while the ratio {\cal B}(Ξ_{c}^{+}\toΞ^{0}π^{+})/{\cal B}(Ξ_{c}^{+}\toΞ^{-}π^{+}π^{+}) is also determined and improved by an order of magnitude in precision. The measured branching fraction ratios are \frac{\cal{B}(Ξ_{c}^{+} \to Σ^{+}K_{S}^{0})}{\cal{B}(Ξ_{c}^{+}\to Ξ^{-}π^{+}π^+)}= 0.067 \pm 0.007 \pm 0.003, \frac{\cal{B}(Ξ_c^{+} \to Ξ^{0}π^{+})}{\cal{B}(Ξ_{c}^{+}\to Ξ^{-}π^{+}π^+)} = 0.248 \pm 0.005 \pm 0.009, \frac{\cal{B}(Ξ_c^{+} \to Ξ^{0}K^{+})}{\cal{B}(Ξ_{c}^{+}\to Ξ^{-}π^{+}π^+)} = 0.017 \pm 0.003 \pm 0.001. Additionally, the ratio {\cal B}(Ξ_{c}^{+}\toΞ^{0}K^{+})/{\cal B}(Ξ_{c}^{+}\toΞ^{0}π^{+}) is measured to be 0.068 \pm 0.010 \pm 0.004. Here, the first and second uncertainties are statistical and systematic, respectively. Multiplying the ratios by the branching fraction of the normalization mode, {\mathcal B}(Ξ_{c}^{+}\toΞ^{-}π^{+}π^+)= (2.9\pm 1.3)\%, we obtain the following absolute branching fractions {\cal B}(Ξ_{c}^{+}\toΣ^{+}K^{0}_{S}) = (0.194 \pm 0.021 \pm 0.009 \pm 0.087 )%, {\cal B}(Ξ_{c}^{+}\toΞ^{0}π^{+}) = (0.719 \pm 0.014 \pm 0.024 \pm 0.322 )%, {\cal B}(Ξ_{c}^{+}\toΞ^{0}K^{+}) = (0.049 \pm 0.007 \pm 0.002 \pm 0.022 )%.
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Submitted 22 March, 2025;
originally announced March 2025.
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Measurement of the Branching Fraction of Λ_c^+ \to p K_S^0 π^0 at Belle
Authors:
The Belle,
Belle II Collaborations,
:,
I. Adachi,
L. Aggarwal,
H. Ahmed,
J. K. Ahn,
H. Aihara,
N. Akopov,
M. Alhakami,
A. Aloisio,
N. Althubiti,
M. Angelsmark,
N. Anh Ky,
D. M. Asner,
H. Atmacan,
T. Aushev,
V. Aushev,
M. Aversano,
R. Ayad,
V. Babu,
H. Bae,
N. K. Baghel,
S. Bahinipati,
P. Bambade
, et al. (404 additional authors not shown)
Abstract:
We report a precise measurement of the ratio of branching fractions \mathcal{B}(Λ_c^+\to p K_S^0 π^0)/\mathcal{B}(Λ_c^+\to p K^- π^+) using 980 fb^{-1} of e^+e^- data from the Belle experiment. We obtain a value of \mathcal{B}(Λ_c^+\to p K_S^0 π^0)/\mathcal{B}(Λ_c^+\to p K^- π^+)=0.339\pm 0.002\pm 0.009, where the first and second uncertainties are statistical and systematic, respectively.…
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We report a precise measurement of the ratio of branching fractions \mathcal{B}(Λ_c^+\to p K_S^0 π^0)/\mathcal{B}(Λ_c^+\to p K^- π^+) using 980 fb^{-1} of e^+e^- data from the Belle experiment. We obtain a value of \mathcal{B}(Λ_c^+\to p K_S^0 π^0)/\mathcal{B}(Λ_c^+\to p K^- π^+)=0.339\pm 0.002\pm 0.009, where the first and second uncertainties are statistical and systematic, respectively. This Belle result is consistent with the previous measurement from the CLEO experiment but has a fivefold improvement in precision. By combining our result with the world average \mathcal{B}(Λ_c^+\to p K^- π^+), we obtain the absolute branching fraction \mathcal{B}(Λ_c^+\to p K_S^0 π^0)=(2.12\pm 0.01\pm 0.05 \pm 0.10)\%, where the uncertainties are statistical, systematic, and the uncertainty in the absolute branching fraction scale \mathcal{B}(Λ_c^+\to p K^- π^+), respectively. This measurement can shed light on hadronic decay mechanisms in charmed baryon decays.
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Submitted 18 March, 2025; v1 submitted 6 March, 2025;
originally announced March 2025.
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Evidence of the P_ccbars(4459)0 in Upsilon(1S, 2S) inclusive decays at Belle
Authors:
I. Adachi,
L. Aggarwal,
H. Ahmed,
J. K. Ahn,
H. Aihara,
N. Akopov,
M. Alhakami,
A. Aloisio,
N. Althubiti,
D. M. Asner,
H. Atmacan,
V. Aushev,
M. Aversano,
R. Ayad,
V. Babu,
H. Bae,
N. K. Baghel,
S. Bahinipati,
P. Bambade,
Sw. Banerjee,
S. Bansal,
M. Barrett,
M. Bartl,
J. Baudot,
A. Baur
, et al. (380 additional authors not shown)
Abstract:
Using data samples of 102 million Upsilon(1S) events and 158 million Upsilon(2S) events collected by the Belle detector at the KEKB asymmetric-energy e^+e^- collider, we search for [udsccbar] pentaquark states decaying to Jpsi Lambda. Using the first observations of Upsilon(1S, 2S) inclusive decays to Jpsi Lambda, we find evidence of the P_ccbars(4459)0 state with a significance of 3.3 standard…
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Using data samples of 102 million Upsilon(1S) events and 158 million Upsilon(2S) events collected by the Belle detector at the KEKB asymmetric-energy e^+e^- collider, we search for [udsccbar] pentaquark states decaying to Jpsi Lambda. Using the first observations of Upsilon(1S, 2S) inclusive decays to Jpsi Lambda, we find evidence of the P_ccbars(4459)0 state with a significance of 3.3 standard deviations, including statistical and systematic uncertainties. We measure the mass and width of the Pccbars(4459)0 to be (4471.7 +- 4.8 +- 0.6) MeV/c2 and (21.9 +- 13.1 +- 2.7) MeV, respectively. The branching fractions for P_ccbars(4459)0 production are measured to be B[Upsilon(1S) -> P_ccbars(4459)0/ Pbar_ccbars(4459)0 + anything] = (3.5 +- 2.0 +- 0.2)*10-6 and B[Upsilin(2S) -> P_ccbars(4459)0/ Pbar_ccbars(4459)0 +anything] = (2.9 +- 1.7 +- 0.4)*10-6. The inclusive branching fractions of Upsilon(1S, 2S) -> Jpsi Lambda/Lambdabar are measured to be B[Upsilin(1S) -> Jpsi Lambda/Lambdabar + anything] = (36.9 +- 5.3 +- 2.4)*10-6 and B[Upsilon(2S) -> Jpsi Lambda/Lambdabar + anything] = (22.3 +- 5.7 +- 3.1)*10-6. We measure the visible cross section σ(e^+e^- \to J/psi Λ/\barΛ + anything) = (90 +- 14 +- 6) fb for the continuum production at \sqrt{s} = 10.52 GeV. In all cases, the first uncertainties are statistical and the second are systematic.
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Submitted 14 February, 2025;
originally announced February 2025.
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Measurement of B^+\toτ^+ν_τ branching fraction with a hadronic tagging method at Belle II
Authors:
Belle II Collaboration,
I. Adachi,
K. Adamczyk,
H. Ahmed,
Y. Ahn,
H. Aihara,
N. Akopov,
M. Alhakami,
A. Aloisio,
N. Althubiti,
M. Angelsmark,
N. Anh Ky,
D. M. Asner,
H. Atmacan,
V. Aushev,
M. Aversano,
R. Ayad,
V. Babu,
N. K. Baghel,
S. Bahinipati,
P. Bambade,
Sw. Banerjee,
M. Bartl,
J. Baudot,
A. Baur
, et al. (319 additional authors not shown)
Abstract:
We present a measurement of the branching fraction of B^+\toτ^+ν_τ decays using (387\pm6)\times 10^6 Υ(4S) collected between 2019 and 2022 with the Belle II detector at the SuperKEKB e^+e^- collider. We reconstruct the accompanying B^- meson using the hadronic tagging method, while B^+\toτ^+ν_τ candidates are identified in the recoil. We find evidence for B^+\toτ^+ν_τ decays at 3.0 s…
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We present a measurement of the branching fraction of B^+\toτ^+ν_τ decays using (387\pm6)\times 10^6 Υ(4S) collected between 2019 and 2022 with the Belle II detector at the SuperKEKB e^+e^- collider. We reconstruct the accompanying B^- meson using the hadronic tagging method, while B^+\toτ^+ν_τ candidates are identified in the recoil. We find evidence for B^+\toτ^+ν_τ decays at 3.0 standard deviations, including systematic uncertainties. The measured branching fraction is \mathcal{B}(B^+\toτ^+ν_τ) = [1.24 \pm 0.41 (\text{stat.}) \pm 0.19 (\text{syst.})] \times 10^{-4}.
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Submitted 7 February, 2025;
originally announced February 2025.
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Measurement of the branching fraction, polarization, and time-dependent CP asymmetry in B^0 \to ρ^+ρ^- decays and constraint on the CKM angle φ_2
Authors:
Belle II Collaboration,
I. Adachi,
L. Aggarwal,
H. Ahmed,
N. Akopov,
M. Alhakami,
A. Aloisio,
N. Althubiti,
N. Anh Ky,
D. M. Asner,
H. Atmacan,
V. Aushev,
M. Aversano,
R. Ayad,
V. Babu,
N. K. Baghel,
P. Bambade,
Sw. Banerjee,
M. Barrett,
M. Bartl,
J. Baudot,
A. Baur,
A. Beaubien,
J. Becker,
J. V. Bennett
, et al. (355 additional authors not shown)
Abstract:
We present a measurement of the branching fraction and fraction of longitudinal polarization of B^0 \to ρ^+ ρ^- decays, which have two π^0's in the final state. We also measure time-dependent {\it CP} violation parameters for decays into longitudinally polarized ρ^+ ρ^- pairs. This analysis is based on a data sample containing (387\pm6) \times 10^6 Υ(4S) mesons collected with the Belle~I…
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We present a measurement of the branching fraction and fraction of longitudinal polarization of B^0 \to ρ^+ ρ^- decays, which have two π^0's in the final state. We also measure time-dependent {\it CP} violation parameters for decays into longitudinally polarized ρ^+ ρ^- pairs. This analysis is based on a data sample containing (387\pm6) \times 10^6 Υ(4S) mesons collected with the Belle~II detector at the SuperKEKB asymmetric-energy e^+e^- collider in 2019-2022. We obtain \mathcal{B}(B^0\toρ^+ρ^-) = (2.89 ^{+0.23}_{-0.22} {}^{+0.29}_{-0.27}) \times 10^{-5}, f_{L} = 0.921 ^{+0.024}_{-0.025} {}^{+0.017}_{-0.015}, \mbox{S = -0.26\pm0.19\pm0.08}, and C = -0.02\pm0.12^{+0.06}_{-0.05}, where the first uncertainties are statistical and the second are systematic. We use these results to perform an isospin analysis to constrain the CKM angle φ_2 and obtain two solutions; the result consistent with other Standard Model constraints is φ_2 = (92.6^{+4.5}_{-4.7})^\circ.
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Submitted 2 May, 2025; v1 submitted 27 December, 2024;
originally announced December 2024.
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Search for lepton flavor-violating decay modes B^0\to K_S^0τ^\pm\ell^\mp~(\ell=μ, e) with hadronic B-tagging at Belle and Belle II
Authors:
Belle,
Belle II Collaborations,
:,
I. Adachi,
K. Adamczyk,
L. Aggarwal,
H. Ahmed,
H. Aihara,
N. Akopov,
M. Alhakami,
A. Aloisio,
N. Althubiti,
N. Anh Ky,
D. M. Asner,
H. Atmacan,
V. Aushev,
M. Aversano,
R. Ayad,
V. Babu,
H. Bae,
N. K. Baghel,
S. Bahinipati,
P. Bambade,
Sw. Banerjee,
S. Bansal
, et al. (403 additional authors not shown)
Abstract:
We present the first search for the lepton flavor-violating decay modes B^0 \rightarrow K_S^0 τ^\pm \ell^\mp~(\ell=μ, e) using the 711 fb^{-1} and 365 fb^{-1} data samples recorded by the Belle and Belle II detectors, respectively. We use a hadronic B-tagging technique, and search for the signal decay in the system recoiling against the fully reconstructed B meson. We find no evidence fo…
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We present the first search for the lepton flavor-violating decay modes B^0 \rightarrow K_S^0 τ^\pm \ell^\mp~(\ell=μ, e) using the 711 fb^{-1} and 365 fb^{-1} data samples recorded by the Belle and Belle II detectors, respectively. We use a hadronic B-tagging technique, and search for the signal decay in the system recoiling against the fully reconstructed B meson. We find no evidence for B^0 \rightarrow K_S^0 τ^\pm \ell^\mp decays and set 90\% confidence level upper limits on the branching fractions in the range of [0.8,\,3.6]\times10^{-5}.
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Submitted 20 December, 2024;
originally announced December 2024.
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Measurement of the branching fraction and \it CP-violating asymmetry of the decay B^{0} \rightarrow π^{0} π^{0} using 387 million bottom-antibottom meson pairs in Belle II data
Authors:
Belle II Collaboration,
I. Adachi,
L. Aggarwal,
H. Ahmed,
H. Aihara,
M. Alhakami,
A. Aloisio,
N. Althubiti,
N. Anh Ky,
D. M. Asner,
H. Atmacan,
V. Aushev,
M. Aversano,
R. Ayad,
V. Babu,
H. Bae,
N. K. Baghel,
S. Bahinipati,
P. Bambade,
Sw. Banerjee,
S. Bansal,
M. Barrett,
M. Bartl,
J. Baudot,
A. Baur
, et al. (415 additional authors not shown)
Abstract:
We measure the branching fraction and \it CP-violating flavor-dependent rate asymmetry of B^{0} \to π^{0} π^{0} decays reconstructed using the Belle II detector in an electron-positron collision sample containing 387 \times 10^{6} B\overline{B} pairs. Using an optimized event selection, we find 126\pm 20 signal decays in a fit to background-discriminating and flavor-sensitive distributio…
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We measure the branching fraction and \it CP-violating flavor-dependent rate asymmetry of B^{0} \to π^{0} π^{0} decays reconstructed using the Belle II detector in an electron-positron collision sample containing 387 \times 10^{6} B\overline{B} pairs. Using an optimized event selection, we find 126\pm 20 signal decays in a fit to background-discriminating and flavor-sensitive distributions. The resulting branching fraction is (1.25 \pm 0.23)\times 10^{-6} and the \it CP-violating asymmetry is 0.03 \pm 0.30.
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Submitted 18 December, 2024;
originally announced December 2024.
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Observation of the decay B^0 \to J/ψω at Belle II
Authors:
Belle II Collaboration,
I. Adachi,
L. Aggarwal,
H. Ahmed,
H. Aihara,
N. Akopov,
M. Alhakami,
A. Aloisio,
N. Althubiti,
N. Anh Ky,
D. M. Asner,
H. Atmacan,
V. Aushev,
M. Aversano,
R. Ayad,
V. Babu,
N. K. Baghel,
S. Bahinipati,
P. Bambade,
Sw. Banerjee,
M. Barrett,
J. Baudot,
A. Baur,
A. Beaubien,
J. Becker
, et al. (361 additional authors not shown)
Abstract:
We measure the branching fraction of the decay B^0 \to J/ψω using data collected with the Belle II detector at the SuperKEKB collider. The data contain (387 \pm 6) \times 10^6 B\overline{B} meson pairs produced in energy-asymmetric e^+e^- collisions at the Υ(4S) resonance. The measured branching fraction \mathcal{B}(B^0 \to J/ψω) = \left( 2.16 \pm 0.30 \pm 0.14 \right) \times 10^{-5},…
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We measure the branching fraction of the decay B^0 \to J/ψω using data collected with the Belle II detector at the SuperKEKB collider. The data contain (387 \pm 6) \times 10^6 B\overline{B} meson pairs produced in energy-asymmetric e^+e^- collisions at the Υ(4S) resonance. The measured branching fraction \mathcal{B}(B^0 \to J/ψω) = \left( 2.16 \pm 0.30 \pm 0.14 \right) \times 10^{-5}, where the first uncertainty is statistical and the second is systematic, is more precise than previous results and constitutes the first observation of the decay with a significance of 6.5 standard deviations.
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Submitted 25 February, 2025; v1 submitted 16 December, 2024;
originally announced December 2024.
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Observations of the singly Cabibbo-suppressed decays Ξ_c^{+} \to pK_{S}^{0}, Ξ_c^+ \to Λπ^+, and Ξ_c^+ \to Σ^{0} π^+ at Belle and Belle II
Authors:
Belle,
Belle II Collaborations,
:,
I. Adachi,
L. Aggarwal,
N. Akopov,
M. Alhakami,
A. Aloisio,
N. Althubiti,
N. Anh Ky,
D. M. Asner,
H. Atmacan,
T. Aushev,
V. Aushev,
M. Aversano,
R. Ayad,
V. Babu,
N. K. Baghel,
S. Bahinipati,
P. Bambade,
Sw. Banerjee,
M. Barrett,
J. Baudot,
A. Baur,
A. Beaubien
, et al. (323 additional authors not shown)
Abstract:
Using data samples of 983.0~\rm fb^{-1} and 427.9~\rm fb^{-1} accumulated with the Belle and Belle~II detectors operating at the KEKB and SuperKEKB asymmetric-energy e^+e^- colliders, singly Cabibbo-suppressed decays Ξ_c^{+} \to pK_{S}^{0}, Ξ_c^+ \to Λπ^+, and Ξ_c^+ \to Σ^{0} π^+ are observed for the first time. The ratios of branching fractions of Ξ_{c}^{+}\to p K_{S}^{0},…
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Using data samples of 983.0~\rm fb^{-1} and 427.9~\rm fb^{-1} accumulated with the Belle and Belle~II detectors operating at the KEKB and SuperKEKB asymmetric-energy e^+e^- colliders, singly Cabibbo-suppressed decays Ξ_c^{+} \to pK_{S}^{0}, Ξ_c^+ \to Λπ^+, and Ξ_c^+ \to Σ^{0} π^+ are observed for the first time. The ratios of branching fractions of Ξ_{c}^{+}\to p K_{S}^{0}, Ξ_{c}^{+}\to Λπ^{+}, and Ξ_{c}^{+}\to Σ^{0} π^{+} relative to that of Ξ_c^+ \to Ξ^- π^{+} π^{+} are measured to be \begin{equation} \frac{{\cal B}(Ξ_c^+ \to pK_S^0)}{{\cal B}(Ξ_c^{+} \to Ξ^{-} π^+ π^+)} = (2.47 \pm 0.16 \pm 0.07)\% \notag, \end{equation} \begin{equation} \frac{{\cal B}(Ξ_c^+ \to Λπ^+)}{{\cal B}(Ξ_c^{+} \to Ξ^{-} π^+ π^+)} = (1.56 \pm 0.14 \pm 0.09)\% \notag, \end{equation} \begin{equation} \frac{{\cal B}(Ξ_c^+ \to Σ^0 π^+)}{{\cal B}(Ξ_c^{+} \to Ξ^{-} π^+ π^+)} = (4.13 \pm 0.26 \pm 0.22)\% \notag. \end{equation} Multiplying these values by the branching fraction of the normalization channel, {\cal B}(Ξ_c^{+} \to Ξ^{-} π^+π^+) = (2.9 \pm 1.3)\%, the absolute branching fractions are determined to be \begin{equation} {\cal B}(Ξ_c^{+} \to p K_{S}^{0}) = (7.16 \pm 0.46 \pm 0.20 \pm 3.21) \times 10^{-4} \notag, \end{equation} \begin{equation} {\cal B}(Ξ_c^{+} \to Λπ^+) = (4.52 \pm 0.41 \pm 0.26 \pm 2.03) \times 10^{-4} \notag, \end{equation} \begin{equation} {\cal B}(Ξ_c^{+} \to Σ^0 π^+) = (1.20 \pm 0.08 \pm 0.07 \pm 0.54) \times 10^{-3} \notag. \end{equation} The first and second uncertainties above are statistical and systematic, respectively, while the third ones arise from the uncertainty in {\cal B}(Ξ_c^{+} \to Ξ^{-} π^{+} π^{+}).
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Submitted 13 December, 2024;
originally announced December 2024.
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Measurement of the inclusive branching fractions for B_s^0 decays into D mesons via hadronic tagging
Authors:
Belle,
Belle II Collaborations,
:,
I. Adachi,
L. Aggarwal,
H. Ahmed,
H. Aihara,
N. Akopov,
A. Aloisio,
S. Al Said,
N. Althubiti,
N. Anh Ky,
D. M. Asner,
H. Atmacan,
T. Aushev,
V. Aushev,
M. Aversano,
R. Ayad,
V. Babu,
H. Bae,
N. K. Baghel,
S. Bahinipati,
P. Bambade,
Sw. Banerjee,
S. Bansal
, et al. (430 additional authors not shown)
Abstract:
We report measurements of the absolute branching fractions \mathcal{B}(B_s^0 \to D_s^{\pm} X), \mathcal{B}(B_s^0 \to D^0/\bar{D}^0 X), and \mathcal{B}(B_s^0 \to D^{\pm} X), where the latter is measured for the first time. The results are based on a 121.4\,fb^{-1} data sample collected at the Υ(10860) resonance by the Belle detector at the KEKB asymmetric-energy e^+ e^- collider. We rec…
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We report measurements of the absolute branching fractions \mathcal{B}(B_s^0 \to D_s^{\pm} X), \mathcal{B}(B_s^0 \to D^0/\bar{D}^0 X), and \mathcal{B}(B_s^0 \to D^{\pm} X), where the latter is measured for the first time. The results are based on a 121.4\,fb^{-1} data sample collected at the Υ(10860) resonance by the Belle detector at the KEKB asymmetric-energy e^+ e^- collider. We reconstruct one B_s^0 meson in e^+e^- \to Υ(10860) \to B_s^{*} \bar{B}_s^{*} events and measure yields of D_s^+, D^0, and D^+ mesons in the rest of the event. We obtain \mathcal{B}(B_s^0 \to D_s^{\pm} X) = (68.6 \pm 7.2 \pm 4.0)\%, \mathcal{B}(B_s^0 \to D^0/\bar{D}^0 X) = (21.5 \pm 6.1 \pm 1.8)\%, and \mathcal{B}(B_s^0 \to D^{\pm} X) = (12.6 \pm 4.6 \pm 1.3)\%, where the first uncertainty is statistical and the second is systematic. Averaging with previous Belle measurements gives \mathcal{B}(B_s^0 \to D_s^{\pm} X) = (63.4 \pm 4.5 \pm 2.2)\% and \mathcal{B}(B_s^0 \to D^0/\bar{D}^0 X) = (23.9 \pm 4.1 \pm 1.8)\%. For the B_s^0 production fraction at the Υ(10860), we find f_s = (21.4^{+1.5}_{-1.7})\%.
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Submitted 18 February, 2025; v1 submitted 21 November, 2024;
originally announced November 2024.
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Production cross sections of light and charmed mesons in e^+e^- annihilation near 10.58 GeV
Authors:
Belle Collaboration,
R. Seidl,
I. Adachi,
H. Aihara,
T. Aushev,
R. Ayad,
Sw. Banerjee,
K. Belous,
J. Bennett,
M. Bessner,
B. Bhuyan,
D. Biswas,
D. Bodrov,
M. Bračko,
P. Branchini,
T. E. Browder,
A. Budano,
M. Campajola,
K. Chilikin,
K. Cho,
S. -K. Choi,
Y. Choi,
S. Choudhury,
S. Das,
G. De Nardo
, et al. (109 additional authors not shown)
Abstract:
We report measurements of production cross sections for ρ^+, ρ^0, ω, K^{*+}, K^{*0}, φ, η, K_S^0, f_0(980), D^+, D^0, D_s^+, D^{*+}, D^{*0}, and D^{*+}_s in e^+e^- collisions at a center-of-mass energy near 10.58 GeV. The data were recorded by the Belle experiment, consisting of 571 fb^{-1} at 10.58 GeV and 74 fb^{-1} at 10.52 GeV. Production cross sections are…
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We report measurements of production cross sections for ρ^+, ρ^0, ω, K^{*+}, K^{*0}, φ, η, K_S^0, f_0(980), D^+, D^0, D_s^+, D^{*+}, D^{*0}, and D^{*+}_s in e^+e^- collisions at a center-of-mass energy near 10.58 GeV. The data were recorded by the Belle experiment, consisting of 571 fb^{-1} at 10.58 GeV and 74 fb^{-1} at 10.52 GeV. Production cross sections are extracted as a function of the fractional hadron momentum x_p . The measurements are compared to {\sc pythia} Monte Carlo generator predictions with various fragmentation settings, including those that have increased fragmentation into vector mesons over pseudo-scalar mesons. The cross sections measured for light hadrons are consistent with no additional increase of vector over pseudo-scalar mesons. The charmed-meson cross sections are compared to earlier measurements -- when available -- including older Belle results, which they supersede. They are in agreement before application of an improved initial-state radiation correction procedure that causes slight changes in their \xp shapes.
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Submitted 13 March, 2025; v1 submitted 18 November, 2024;
originally announced November 2024.
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Measurement of B \to K{}^{*}(892)γ decays at Belle II
Authors:
Belle II Collaboration,
I. Adachi,
L. Aggarwal,
H. Ahmed,
H. Aihara,
N. Akopov,
A. Aloisio,
N. Althubiti,
N. Anh Ky,
D. M. Asner,
H. Atmacan,
T. Aushev,
V. Aushev,
M. Aversano,
R. Ayad,
V. Babu,
H. Bae,
N. K. Baghel,
S. Bahinipati,
P. Bambade,
Sw. Banerjee,
S. Bansal,
M. Barrett,
M. Bartl,
J. Baudot
, et al. (429 additional authors not shown)
Abstract:
We present measurements of B \to K{}^{*}(892)γ decays using 365\,{\rm fb}^{-1} of data collected from 2019 to 2022 by the Belle~II experiment at the SuperKEKB asymmetric-energy e^+e^- collider. The data sample contains (387 \pm 6) \times 10^6 Υ(4S) events. We measure branching fractions (\mathcal{B}) and C\!P asymmetries (\mathcal{A}_{C\!P}) for both B^{0}\to K{}^{*0}γ and…
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We present measurements of B \to K{}^{*}(892)γ decays using 365\,{\rm fb}^{-1} of data collected from 2019 to 2022 by the Belle~II experiment at the SuperKEKB asymmetric-energy e^+e^- collider. The data sample contains (387 \pm 6) \times 10^6 Υ(4S) events. We measure branching fractions (\mathcal{B}) and C\!P asymmetries (\mathcal{A}_{C\!P}) for both B^{0}\to K{}^{*0}γ and B^{+}\to K{}^{*+}γ decays. The difference in C\!P asymmetries (Δ\mathcal{A}_{C\!P}) and the isospin asymmetry (Δ_{0+}) between these neutral and charged channels are also measured. We obtain the following branching fractions and C\!P asymmetries: \mathcal{B} (B^{0} \to K{}^{*0}γ) = (4.14 \pm 0.10 \pm 0.11 ) \times 10^{-5}, \mathcal{B} (B^{+} \to K{}^{*+}γ) = (4.04 \pm 0.13 {}^{+0.13}_{-0.15} )\times 10^{-5}, \mathcal{A}_{C\!P} (B^{0} \to K{}^{*0}γ) = (-3.3 \pm 2.3 \pm 0.4 )\%, and \mathcal{A}_{C\!P} (B^{+} \to K{}^{*+}γ) = (-0.7 \pm 2.9 \pm 0.5 )\%. The measured difference in C\!P asymmetries is Δ\mathcal{A}_{C\!P} = (+2.6 \pm 3.8 \pm 0.6 )\%, and the measured isospin asymmetry is Δ_{0+} = (+4.8 \pm 2.0 \pm 1.8 )\%. The first uncertainties listed are statistical and the second are systematic. These results are consistent with world-average values and theory predictions.
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Submitted 19 March, 2025; v1 submitted 15 November, 2024;
originally announced November 2024.
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Measurement of the time-integrated CP asymmetry in D^{0}\rightarrow K^{0}_{S}K^{0}_{S} decays using Belle and Belle II data
Authors:
Belle,
Belle II Collaborations,
:,
I. Adachi,
L. Aggarwal,
H. Ahmed,
H. Aihara,
N. Akopov,
A. Aloisio,
N. Althubiti,
N. Anh Ky,
D. M. Asner,
H. Atmacan,
V. Aushev,
M. Aversano,
R. Ayad,
V. Babu,
N. K. Baghel,
S. Bahinipati,
P. Bambade,
Sw. Banerjee,
S. Bansal,
M. Barrett,
M. Bartl,
J. Baudot
, et al. (338 additional authors not shown)
Abstract:
We measure the time-integrated CP asymmetry in D^{0} \rightarrow K^{0}_{S}K^{0}_{S} decays reconstructed in e^{+}e^{-} \rightarrow c\overline{c} events collected by the Belle and Belle II experiments. The corresponding data samples have integrated luminosities of 980 fb^{-1} and 428 fb^{-1}, respectively. The D^{0} decays are required to originate from the…
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We measure the time-integrated CP asymmetry in D^{0} \rightarrow K^{0}_{S}K^{0}_{S} decays reconstructed in e^{+}e^{-} \rightarrow c\overline{c} events collected by the Belle and Belle II experiments. The corresponding data samples have integrated luminosities of 980 fb^{-1} and 428 fb^{-1}, respectively. The D^{0} decays are required to originate from the D^{*+} \rightarrow D^{0}π^{+} decay, which determines the charm flavor at production time. A control sample of D^{0} \rightarrow K^{+}K^{-} decays is used to correct for production and detection asymmetries. The result, (-1.4\pm1.3{\rm(stat)}\pm0.1{\rm (syst)})\%, is consistent with previous determinations and with CP symmetry.
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Submitted 4 February, 2025; v1 submitted 31 October, 2024;
originally announced November 2024.
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Model-independent measurement of D^0-\overline{D}{}^0 mixing parameters in D^0\rightarrow K^0_{S}π^+π^- decays at Belle and Belle II
Authors:
Belle,
Belle II Collaborations,
:,
I. Adachi,
L. Aggarwal,
H. Ahmed,
H. Aihara,
N. Akopov,
A. Aloisio,
N. Althubiti,
N. Anh Ky,
D. M. Asner,
H. Atmacan,
V. Aushev,
M. Aversano,
R. Ayad,
N. K. Baghel,
P. Bambade,
Sw. Banerjee,
S. Bansal,
M. Barrett,
M. Bartl,
J. Baudot,
A. Beaubien,
J. Becker
, et al. (317 additional authors not shown)
Abstract:
We perform a model-independent measurement of the D^0-\overline{D}{}^0 mixing parameters using samples of e^+e^--collision data collected by the Belle and Belle II experiments that have integrated luminosities of 951\ \text{fb}^{-1} and 408\ \text{fb}^{-1}, respectively. Approximately 2.05\times10^6 neutral D mesons are reconstructed in the D^0\rightarrow K^0_{S}π^+π^- channel, wit…
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We perform a model-independent measurement of the D^0-\overline{D}{}^0 mixing parameters using samples of e^+e^--collision data collected by the Belle and Belle II experiments that have integrated luminosities of 951\ \text{fb}^{-1} and 408\ \text{fb}^{-1}, respectively. Approximately 2.05\times10^6 neutral D mesons are reconstructed in the D^0\rightarrow K^0_{S}π^+π^- channel, with the neutral D flavor tagged by the charge of the pion in the D^{*+}\rightarrow D^0π^+ decay. Assuming charge-parity symmetry, the mixing parameters are measured to be x = (4.0\pm1.7\pm0.4)\times 10^{-3} and y = (2.9\pm1.4\pm0.3)\times 10^{-3}, where the first uncertainties are statistical and the second systematic. The results are consistent with previous determinations.
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Submitted 7 May, 2025; v1 submitted 30 October, 2024;
originally announced October 2024.
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Observation of time-dependent CP violation and measurement of the branching fraction of B^0 \to J/ψπ^0 decays
Authors:
Belle II Collaboration,
I. Adachi,
L. Aggarwal,
H. Ahmed,
H. Aihara,
N. Akopov,
A. Aloisio,
N. Althubiti,
N. Anh Ky,
D. M. Asner,
H. Atmacan,
V. Aushev,
M. Aversano,
R. Ayad,
V. Babu,
H. Bae,
N. K. Baghel,
S. Bahinipati,
P. Bambade,
Sw. Banerjee,
S. Bansal,
J. Baudot,
A. Baur,
A. Beaubien,
F. Becherer
, et al. (369 additional authors not shown)
Abstract:
We present a measurement of the branching fraction and time-dependent charge-parity (CP) decay-rate asymmetries in B^0 \to J/ψπ^0 decays. The data sample was collected with the Belle~II detector at the SuperKEKB asymmetric e^+e^- collider in 2019-2022 and contains (387\pm 6)\times 10^6 B\overline{B} meson pairs from Υ(4S) decays. We reconstruct 392\pm 24 signal decays and fit the…
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We present a measurement of the branching fraction and time-dependent charge-parity (CP) decay-rate asymmetries in B^0 \to J/ψπ^0 decays. The data sample was collected with the Belle~II detector at the SuperKEKB asymmetric e^+e^- collider in 2019-2022 and contains (387\pm 6)\times 10^6 B\overline{B} meson pairs from Υ(4S) decays. We reconstruct 392\pm 24 signal decays and fit the CP parameters from the distribution of the proper-decay-time difference of the two B mesons. We measure the branching fraction to be B(B^0 \to J/ψπ^0)=(2.00 \pm 0.12 \pm 0.09)\times 10^{-5} and the direct and mixing-induced CP asymmetries to be C_{CP}=0.13 \pm 0.12 \pm 0.03 and S_{CP}=-0.88 \pm 0.17 \pm 0.03, respectively, where the first uncertainties are statistical and the second are systematic. We observe mixing-induced CP violation with a significance of 5.0 standard deviations for the first time in this mode.
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Submitted 27 January, 2025; v1 submitted 11 October, 2024;
originally announced October 2024.
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TCAD Simulation of Stitching for Passive CMOS Strip Detectors
Authors:
Marta Baselga,
Jan Hendrik Arling,
Naomi Davis,
Jochen Dingfelder,
Ingrid-Maria Gregor,
Marc Hauser,
Fabian Huegging,
Karl Jakobs,
Michael Karagounis,
Roland Koppenhoefer,
Kevin Kroeninger,
Fabian Lex,
Ulrich Parzefall,
Birkan Sari,
Simon Spannagel,
Dennis Sperlich,
Jens Weingarten,
Iveta Zatocilova
Abstract:
Most of the tracking detectors for high energy particle experiments are filled with silicon detectors since they are radiation hard, they can give very small spatial resolution and they can take advantage of the silicon electronics foundries developments and production lines.
Strip detectors are very useful to cover large areas for tracking purposes, while consuming less power per area compared…
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Most of the tracking detectors for high energy particle experiments are filled with silicon detectors since they are radiation hard, they can give very small spatial resolution and they can take advantage of the silicon electronics foundries developments and production lines.
Strip detectors are very useful to cover large areas for tracking purposes, while consuming less power per area compared to pixel sensors. The majority of particle physics experiments use conventional silicon strip detectors fabricated in foundries that do not use stitching, relying on a very small number of foundries worldwide that can provide large amounts of strip detectors. Fabricating strip detectors in a CMOS foundry opens the possibility to use more foundries and to include active elements in the strips for future productions. For the passive CMOS strip detectors project we fabricated strip detectors in a CMOS foundry using two 1 cm2 reticles that are stitched together along the wafer. The fabricated strips stitched the reticles three and five times, and it was shown that the performance of those strips is not affected by the stitching.
This paper shows 3D TCAD simulations of the stitching area to investigate the possible effects stitching can have on the performance of the strip detectors, considering different stitching mismatches. We will show that the mismatch of stitched structures up to 1 um does not impact the performance with TCAD simulations which agrees with the results obtained from the measurements.
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Submitted 19 November, 2024; v1 submitted 26 September, 2024;
originally announced September 2024.
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Search for C\!P violation in D^+_{(s)}\to{}K_{S}^{0}K^{-}π^{+}π^{+} decays using triple and quadruple products
Authors:
Belle,
Belle II Collaborations,
:,
L. Aggarwal,
H. Ahmed,
H. Aihara,
N. Akopov,
A. Aloisio,
N. Althubiti,
N. Anh Ky,
D. M. Asner,
H. Atmacan,
V. Aushev,
M. Aversano,
R. Ayad,
V. Babu,
H. Bae,
N. K. Baghel,
S. Bahinipati,
P. Bambade,
Sw. Banerjee,
J. Baudot,
A. Baur,
A. Beaubien,
F. Becherer
, et al. (344 additional authors not shown)
Abstract:
We perform the first search for C\!P violation in {D_{(s)}^{+}\to{}K_{S}^{0}K^{-}π^{+}π^{+}} decays. We use a combined data set from the Belle and Belle II experiments, which study e^+e^- collisions at center-of-mass energies at or near the Υ(4S) resonance. We use 980 fb^{-1} of data from Belle and 428 fb^{-1} of data from Belle~II. We measure six C\!P-violating asymmetries that are…
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We perform the first search for C\!P violation in {D_{(s)}^{+}\to{}K_{S}^{0}K^{-}π^{+}π^{+}} decays. We use a combined data set from the Belle and Belle II experiments, which study e^+e^- collisions at center-of-mass energies at or near the Υ(4S) resonance. We use 980 fb^{-1} of data from Belle and 428 fb^{-1} of data from Belle~II. We measure six C\!P-violating asymmetries that are based on triple products and quadruple products of the momenta of final-state particles, and also the particles' helicity angles. We obtain a precision at the level of 0.5% for D^+\to{}K_{S}^{0}K^{-}π^{+}π^{+} decays, and better than 0.3% for D^+_{s}\to{}K_{S}^{0}K^{-}π^{+}π^{+} decays. No evidence of C\!P violation is found. Our results for the triple-product asymmetries are the most precise to date for singly-Cabibbo-suppressed D^+ decays. Our results for the other asymmetries are the first such measurements performed for charm decays.
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Submitted 12 February, 2025; v1 submitted 24 September, 2024;
originally announced September 2024.
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Determination of |V_{ub}| from simultaneous measurements of untagged B^0\toπ^- \ell^+ ν_{\ell} and B^+\toρ^0 \ell^+ν_{\ell} decays
Authors:
Belle II Collaboration,
I. Adachi,
L. Aggarwal,
H. Aihara,
N. Akopov,
A. Aloisio,
N. Althubiti,
N. Anh Ky,
D. M. Asner,
H. Atmacan,
T. Aushev,
V. Aushev,
M. Aversano,
R. Ayad,
V. Babu,
H. Bae,
S. Bahinipati,
P. Bambade,
Sw. Banerjee,
S. Bansal,
M. Barrett,
J. Baudot,
M. Bauer,
A. Baur,
A. Beaubien
, et al. (395 additional authors not shown)
Abstract:
We present a measurement of |V_{ub}| from a simultaneous study of the charmless semileptonic decays B^0\toπ^- \ell^+ ν_{\ell} and B^+\toρ^0 \ell^+ν_{\ell}, where \ell = e, μ. This measurement uses a data sample of 387 million B\overline{B} meson pairs recorded by the Belle~II detector at the SuperKEKB electron-positron collider between 2019 and 2022. The two decays are reconstructed with…
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We present a measurement of |V_{ub}| from a simultaneous study of the charmless semileptonic decays B^0\toπ^- \ell^+ ν_{\ell} and B^+\toρ^0 \ell^+ν_{\ell}, where \ell = e, μ. This measurement uses a data sample of 387 million B\overline{B} meson pairs recorded by the Belle~II detector at the SuperKEKB electron-positron collider between 2019 and 2022. The two decays are reconstructed without identifying the partner B mesons. We simultaneously measure the differential branching fractions of B^0\toπ^- \ell^+ ν_{\ell} and B^+\toρ^0 \ell^+ν_{\ell} decays as functions of q^2 (momentum transfer squared). From these, we obtain total branching fractions B(B^0\toπ^- \ell^+ ν_{\ell}) = (1.516 \pm 0.042 (\mathrm{stat}) \pm 0.059 (\mathrm{syst})) \times 10^{-4} and B(B^+\toρ^0 \ell^+ν_{\ell}) = (1.625 \pm 0.079 (\mathrm{stat}) \pm 0.180 (\mathrm{syst})) \times 10^{-4}. By fitting the measured B^0\toπ^- \ell^+ ν_{\ell} partial branching fractions as functions of q^2, together with constraints on the non-perturbative hadronic contribution from lattice QCD calculations, we obtain |V_{ub}| = (3.93 \pm 0.09 \pm 0.13 \pm 0.19) \times 10^{-3}. Here, the first uncertainty is statistical, the second is systematic, and the third is theoretical.
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Submitted 24 July, 2024;
originally announced July 2024.
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Measurement of CP asymmetries in B^0 \to K^0_S π^0 γ decays at Belle II
Authors:
Belle II Collaboration,
I. Adachi,
L. Aggarwal,
H. Ahmed,
H. Aihara,
N. Akopov,
A. Aloisio,
N. Anh Ky,
D. M. Asner,
H. Atmacan,
T. Aushev,
V. Aushev,
M. Aversano,
R. Ayad,
V. Babu,
H. Bae,
S. Bahinipati,
P. Bambade,
Sw. Banerjee,
S. Bansal,
M. Barrett,
J. Baudot,
A. Baur,
A. Beaubien,
F. Becherer
, et al. (414 additional authors not shown)
Abstract:
We report measurements of time-dependent CP asymmetries in B^0 \to K^0_S π^0 γ decays based on a data sample of (388\pm6)\times10^6 B\bar{B} events collected at the Υ(4S) resonance with the Belle II detector. The Belle II experiment operates at the SuperKEKB asymmetric-energy e^+e^- collider. We measure decay-time distributions to determine CP-violating parameters S and C. We det…
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We report measurements of time-dependent CP asymmetries in B^0 \to K^0_S π^0 γ decays based on a data sample of (388\pm6)\times10^6 B\bar{B} events collected at the Υ(4S) resonance with the Belle II detector. The Belle II experiment operates at the SuperKEKB asymmetric-energy e^+e^- collider. We measure decay-time distributions to determine CP-violating parameters S and C. We determine these parameters for two ranges of K^0_S π^0 invariant mass: m(K^0_S π^0)\in (0.8, 1.0) GeV/c^2, which is dominated by B^0 \to K^{*0} (\to K^0_S π^0) γ decays, and a complementary region m(K^0_S π^0)\in (0.6, 0.8)\cup(1.0, 1.8) GeV/c^2. Our results have improved precision as compared to previous measurements and are consistent with theory predictions.
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Submitted 12 July, 2024;
originally announced July 2024.
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Measurement of branching fractions, CP asymmetry, and isospin asymmetry for \boldsymbol{B\rightarrowργ} decays using Belle and Belle II data
Authors:
Belle II Collaboration,
I. Adachi,
K. Adamczyk,
L. Aggarwal,
H. Aihara,
N. Akopov,
A. Aloisio,
N. Anh Ky,
D. M. Asner,
H. Atmacan,
T. Aushev,
V. Aushev,
M. Aversano,
R. Ayad,
V. Babu,
H. Bae,
S. Bahinipati,
P. Bambade,
Sw. Banerjee,
S. Bansal,
M. Barrett,
J. Baudot,
A. Baur,
A. Beaubien,
F. Becherer
, et al. (385 additional authors not shown)
Abstract:
We present measurements of B^{+}\rightarrowρ^{+}γ and B^{0}\rightarrowρ^{0}γ decays using a combined data sample of 772 \times 10^6 B\overline{B} pairs collected by the Belle experiment and 387\times 10^6 B\overline{B} pairs collected by the Belle II experiment in e^{+}e^{-} collisions at the Υ(4S) resonance. After an optimized selection, a simultaneous fit to the Belle and Belle I…
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We present measurements of B^{+}\rightarrowρ^{+}γ and B^{0}\rightarrowρ^{0}γ decays using a combined data sample of 772 \times 10^6 B\overline{B} pairs collected by the Belle experiment and 387\times 10^6 B\overline{B} pairs collected by the Belle II experiment in e^{+}e^{-} collisions at the Υ(4S) resonance. After an optimized selection, a simultaneous fit to the Belle and Belle II data sets yields 114\pm 12 B^{+}\rightarrowρ^{+}γ and 99\pm 12 B^{0}\rightarrowρ^{0}γ decays. The measured branching fractions are (13.1^{+2.0 +1.3}_{-1.9 -1.2})\times 10^{-7} and (7.5\pm 1.3^{+1.0}_{-0.8})\times 10^{-7} for B^{+}\rightarrowρ^{+}γ and B^{0}\rightarrowρ^{0}γ decays, respectively, where the first uncertainty is statistical and the second is systematic. We also measure the isospin asymmetry A_{\rm I}(B\rightarrowργ)=(10.9^{+11.2 +7.8}_{-11.7 -7.3})\% and the direct CP asymmetry A_{CP}(B^{+}\rightarrowρ^{+}γ)=(-8.2\pm 15.2^{+1.6}_{-1.2})\%.
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Submitted 12 July, 2024;
originally announced July 2024.
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Search for the baryon number and lepton number violating decays τ^-\to Λπ^- and τ^-\to \barΛπ^- at Belle II
Authors:
Belle II Collaboration,
I. Adachi,
L. Aggarwal,
H. Ahmed,
H. Aihara,
N. Akopov,
A. Aloisio,
N. Althubiti,
N. Anh Ky,
D. M. Asner,
H. Atmacan,
T. Aushev,
V. Aushev,
M. Aversano,
R. Ayad,
V. Babu,
H. Bae,
S. Bahinipati,
P. Bambade,
Sw. Banerjee,
S. Bansal,
M. Barrett,
J. Baudot,
A. Baur,
A. Beaubien
, et al. (349 additional authors not shown)
Abstract:
We present a search for the baryon number B and lepton number L violating decays τ^- \rightarrow Λπ^- and τ^- \rightarrow \barΛ π^- produced from the e^+e^-\to τ^+τ^- process, using a 364 fb^{-1} data sample collected by the Belle~II experiment at the SuperKEKB collider. No evidence of signal is found in either decay mode, which have |Δ(B-L)| equal to 2 and 0, respectively. Upper…
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We present a search for the baryon number B and lepton number L violating decays τ^- \rightarrow Λπ^- and τ^- \rightarrow \barΛ π^- produced from the e^+e^-\to τ^+τ^- process, using a 364 fb^{-1} data sample collected by the Belle~II experiment at the SuperKEKB collider. No evidence of signal is found in either decay mode, which have |Δ(B-L)| equal to 2 and 0, respectively. Upper limits at 90\% credibility level on the branching fractions of τ^- \rightarrow Λπ^- and τ^- \rightarrow \barΛπ^- are determined to be 4.7 \times 10^{-8} and 4.3 \times 10^{-8}, respectively.
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Submitted 6 July, 2024;
originally announced July 2024.
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Measurement of the integrated luminosity of data samples collected during 2019-2022 by the Belle II experiment
Authors:
The Belle II Collaboration,
I. Adachi,
L. Aggarwal,
H. Ahmed,
J. K. Ahn,
H. Aihara,
N. Akopov,
A. Aloisio,
N. Althubiti,
N. Anh Ky,
D. M. Asner,
H. Atmacan,
T. Aushev,
V. Aushev,
M. Aversano,
R. Ayad,
V. Babu,
H. Bae,
S. Bahinipati,
P. Bambade,
Sw. Banerjee,
M. Barrett,
J. Baudot,
A. Baur,
A. Beaubien
, et al. (382 additional authors not shown)
Abstract:
A series of data samples was collected with the Belle~II detector at the SuperKEKB collider from March 2019 to June 2022. We determine the integrated luminosities of these data samples using three distinct methodologies involving Bhabha (e^+e^- \to e^+e^-(nγ)), digamma (e^+e^- \to γγ(nγ)), and dimuon (e^+e^- \to μ^+ μ^- (nγ)) events. The total integrated luminosity obtained with Bhabha, diga…
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A series of data samples was collected with the Belle~II detector at the SuperKEKB collider from March 2019 to June 2022. We determine the integrated luminosities of these data samples using three distinct methodologies involving Bhabha (e^+e^- \to e^+e^-(nγ)), digamma (e^+e^- \to γγ(nγ)), and dimuon (e^+e^- \to μ^+ μ^- (nγ)) events. The total integrated luminosity obtained with Bhabha, digamma, and dimuon events is ({426.88} \pm 0.03 \pm {2.61})~fb^{-1}, ({429.28} \pm 0.03 \pm {2.62})~fb^{-1}, and ({423.99} \pm 0.04 \pm {3.83})~fb^{-1}, where the first uncertainties are statistical and the second are systematic. The resulting total integrated luminosity obtained from the combination of the three methods is ({427.87 \pm 2.01})~fb^{-1}.
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Submitted 19 September, 2024; v1 submitted 1 July, 2024;
originally announced July 2024.
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The Belle II Detector Upgrades Framework Conceptual Design Report
Authors:
H. Aihara,
A. Aloisio,
D. P. Auguste,
M. Aversano,
M. Babeluk,
S. Bahinipati,
Sw. Banerjee,
M. Barbero,
J. Baudot,
A. Beaubien,
F. Becherer,
T. Bergauer,
F. U. Bernlochner.,
V. Bertacchi,
G. Bertolone,
C. Bespin,
M. Bessner,
S. Bettarini,
A. J. Bevan,
B. Bhuyan,
M. Bona,
J. F. Bonis,
J. Borah,
F. Bosi,
R. Boudagga
, et al. (186 additional authors not shown)
Abstract:
We describe the planned near-term and potential longer-term upgrades of the Belle II detector at the SuperKEKB electron-positron collider operating at the KEK laboratory in Tsukuba, Japan. These upgrades will allow increasingly sensitive searches for possible new physics beyond the Standard Model in flavor, tau, electroweak and dark sector physics that are both complementary to and competitive wit…
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We describe the planned near-term and potential longer-term upgrades of the Belle II detector at the SuperKEKB electron-positron collider operating at the KEK laboratory in Tsukuba, Japan. These upgrades will allow increasingly sensitive searches for possible new physics beyond the Standard Model in flavor, tau, electroweak and dark sector physics that are both complementary to and competitive with the LHC and other experiments.
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Submitted 4 July, 2024; v1 submitted 26 June, 2024;
originally announced June 2024.
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Search for charmed baryons in the Λ_c^+η system and measurement of the branching fractions of Λ_c(2880)^+ and Λ_c(2940)^+ decaying to Λ_c^+η and pD^0 relative to Σ_c(2455)π
Authors:
Belle Collaboration,
S. X. Li,
C. P. Shen,
I. Adachi,
J. K. Ahn,
H. Aihara,
D. M. Asner,
H. Atmacan,
T. Aushev,
R. Ayad,
Sw. Banerjee,
K. Belous,
J. Bennett,
M. Bessner,
T. Bilka,
D. Biswas,
D. Bodrov,
A. Bozek,
M. Bračko,
P. Branchini,
T. E. Browder,
A. Budano,
M. Campajola,
M. -C. Chang,
B. G. Cheon
, et al. (103 additional authors not shown)
Abstract:
We search for excited charmed baryons in the Λ_c^+η system using a data sample corresponding to an integrated luminosity of 980 \rm fb^{-1}. The data were collected by the Belle detector at the KEKB e^{+}e^{-} asymmetric-energy collider. No significant signals are found in the Λ_c^+η mass spectrum, including the known Λ_c(2880)^+ and Λ_c(2940)^+. Clear Λ_c(2880)^+ and…
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We search for excited charmed baryons in the Λ_c^+η system using a data sample corresponding to an integrated luminosity of 980 \rm fb^{-1}. The data were collected by the Belle detector at the KEKB e^{+}e^{-} asymmetric-energy collider. No significant signals are found in the Λ_c^+η mass spectrum, including the known Λ_c(2880)^+ and Λ_c(2940)^+. Clear Λ_c(2880)^+ and Λ_c(2940)^+ signals are observed in the pD^0 mass spectrum. We set upper limits at 90\% credibility level on ratios of branching fractions of Λ_c(2880)^+ and Λ_c(2940)^+ decaying to Λ_c^+η relative to Σ_c(2455)π of <0.13 for the Λ_c(2880)^+ and <1.11 for the Λ_c(2940)^+. We measure ratios of branching fractions of Λ_c(2880)^+ and Λ_c(2940)^+ decaying to pD^0 relative to Σ_c(2455)π of 0.75 \pm 0.03(\text{stat.}) \pm 0.07(\text{syst.}) for the Λ_c(2880)^+ and 3.59 \pm 0.21(\text{stat.}) \pm 0.56(\text{syst.}) for the Λ_c(2940)^+.
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Submitted 28 July, 2024; v1 submitted 22 June, 2024;
originally announced June 2024.
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Measurement of the branching fractions of \bar{B}\to D^{(*)} K^- K^{(*)0}_{(S)} and \bar{B}\to D^{(*)}D_s^{-} decays at Belle II
Authors:
Belle II Collaboration,
I. Adachi,
L. Aggarwal,
H. Aihara,
N. Akopov,
A. Aloisio,
N. Althubiti,
N. Anh Ky,
D. M. Asner,
H. Atmacan,
T. Aushev,
V. Aushev,
M. Aversano,
R. Ayad,
V. Babu,
H. Bae,
S. Bahinipati,
P. Bambade,
Sw. Banerjee,
S. Bansal,
M. Barrett,
J. Baudot,
A. Baur,
A. Beaubien,
F. Becherer
, et al. (382 additional authors not shown)
Abstract:
We present measurements of the branching fractions of eight \overline B{}^0\to D^{(*)+} K^- K^{(*)0}_{(S)}, B^{-}\to D^{(*)0} K^- K^{(*)0}_{(S)} decay channels. The results are based on data from SuperKEKB electron-positron collisions at the Υ(4S) resonance collected with the Belle II detector, corresponding to an integrated luminosity of 362~\text{fb}^{-1}. The event yields are extracted…
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We present measurements of the branching fractions of eight \overline B{}^0\to D^{(*)+} K^- K^{(*)0}_{(S)}, B^{-}\to D^{(*)0} K^- K^{(*)0}_{(S)} decay channels. The results are based on data from SuperKEKB electron-positron collisions at the Υ(4S) resonance collected with the Belle II detector, corresponding to an integrated luminosity of 362~\text{fb}^{-1}. The event yields are extracted from fits to the distributions of the difference between expected and observed B meson energy, and are efficiency-corrected as a function of m(K^-K^{(*)0}_{(S)}) and m(D^{(*)}K^{(*)0}_{(S)}) in order to avoid dependence on the decay model. These results include the first observation of \overline B{}^0\to D^+K^-K_S^0, B^-\to D^{*0}K^-K_S^0, and \overline B{}^0\to D^{*+}K^-K_S^0 decays and a significant improvement in the precision of the other channels compared to previous measurements. The helicity-angle distributions and the invariant mass distributions of the K^- K^{(*)0}_{(S)} systems are compatible with quasi-two-body decays via a resonant transition with spin-parity J^P=1^- for the K^-K_S^0 systems and J^P= 1^+ for the K^-K^{*0} systems. We also present measurements of the branching fractions of four \overline B{}^0\to D^{(*)+} D_s^-, B^{-}\to D^{(*)0} D_s^- decay channels with a precision compatible to the current world averages.
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Submitted 4 September, 2024; v1 submitted 10 June, 2024;
originally announced June 2024.
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Measurements of the branching fractions of Ξ_{c}^{0}\toΞ^{0}π^{0}, Ξ_{c}^{0}\toΞ^{0}η, and Ξ_{c}^{0}\toΞ^{0}η^{\prime} and asymmetry parameter of Ξ_{c}^{0}\toΞ^{0}π^{0}
Authors:
Belle,
Belle II Collaborations,
:,
I. Adachi,
L. Aggarwal,
H. Aihara,
N. Akopov,
A. Aloisio,
N. Althubiti,
N. Anh Ky,
D. M. Asner,
H. Atmacan,
T. Aushev,
V. Aushev,
M. Aversano,
R. Ayad,
V. Babu,
H. Bae,
S. Bahinipati,
P. Bambade,
Sw. Banerjee,
M. Barrett,
J. Baudot,
A. Baur,
A. Beaubien
, et al. (360 additional authors not shown)
Abstract:
We present a study of Ξ_{c}^{0}\toΞ^{0}π^{0}, Ξ_{c}^{0}\toΞ^{0}η, and Ξ_{c}^{0}\toΞ^{0}η^{\prime} decays using the Belle and Belle~II data samples, which have integrated luminosities of 980~\mathrm{fb}^{-1} and 426~\mathrm{fb}^{-1}, respectively. We measure the following relative branching fractions…
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We present a study of Ξ_{c}^{0}\toΞ^{0}π^{0}, Ξ_{c}^{0}\toΞ^{0}η, and Ξ_{c}^{0}\toΞ^{0}η^{\prime} decays using the Belle and Belle~II data samples, which have integrated luminosities of 980~\mathrm{fb}^{-1} and 426~\mathrm{fb}^{-1}, respectively. We measure the following relative branching fractions {\cal B}(Ξ_{c}^{0}\toΞ^{0}π^{0})/{\cal B}(Ξ_{c}^{0}\toΞ^{-}π^{+}) = 0.48 \pm 0.02 ({\rm stat}) \pm 0.03 ({\rm syst}) , {\cal B}(Ξ_{c}^{0}\toΞ^{0}η)/{\cal B}(Ξ_{c}^{0}\toΞ^{-}π^{+}) = 0.11 \pm 0.01 ({\rm stat}) \pm 0.01 ({\rm syst}) , {\cal B}(Ξ_{c}^{0}\toΞ^{0}η^{\prime})/{\cal B}(Ξ_{c}^{0}\toΞ^{-}π^{+}) = 0.08 \pm 0.02 ({\rm stat}) \pm 0.01 ({\rm syst}) for the first time, where the uncertainties are statistical (\rm stat) and systematic (\rm syst). By multiplying by the branching fraction of the normalization mode, {\mathcal B}(Ξ_{c}^{0}\toΞ^{-}π^{+}), we obtain the following absolute branching fraction results (6.9 \pm 0.3 ({\rm stat}) \pm 0.5 ({\rm syst}) \pm 1.3 ({\rm norm})) \times 10^{-3}, (1.6 \pm 0.2 ({\rm stat}) \pm 0.2 ({\rm syst}) \pm 0.3 ({\rm norm})) \times 10^{-3}, and (1.2 \pm 0.3 ({\rm stat}) \pm 0.1 ({\rm syst}) \pm 0.2 ({\rm norm})) \times 10^{-3}, for Ξ_{c}^{0} decays to Ξ^{0}π^{0}, Ξ^{0}η, and Ξ^{0}η^{\prime} final states, respectively. The third errors are from the uncertainty on {\mathcal B}(Ξ_{c}^{0}\toΞ^{-}π^{+}). The asymmetry parameter for Ξ_{c}^{0}\toΞ^{0}π^{0} is measured to be α(Ξ_{c}^{0}\toΞ^{0}π^{0}) = -0.90\pm0.15({\rm stat})\pm0.23({\rm syst}).
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Submitted 5 October, 2024; v1 submitted 7 June, 2024;
originally announced June 2024.
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Search for the decay B^{0}\toγγ using Belle and Belle II data
Authors:
Belle,
Belle II Collaborations,
:,
I. Adachi,
L. Aggarwal,
H. Aihara,
N. Akopov,
A. Aloisio,
S. Al Said,
N. Althubiti,
N. Anh Ky,
D. M. Asner,
H. Atmacan,
T. Aushev,
V. Aushev,
M. Aversano,
R. Ayad,
V. Babu,
H. Bae,
S. Bahinipati,
P. Bambade,
Sw. Banerjee,
S. Bansal,
M. Barrett,
J. Baudot
, et al. (385 additional authors not shown)
Abstract:
We report the result of a search for the rare decay B^{0} \to γγ using a combined dataset of 753\times10^{6} B\bar{B} pairs collected by the Belle experiment and 387\times10^{6} B\bar{B} pairs collected by the Belle II experiment from decays of the \rm Υ(4S) resonance produced in e^{+}e^{-} collisions. A simultaneous fit to the Belle and Belle II data sets yields…
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We report the result of a search for the rare decay B^{0} \to γγ using a combined dataset of 753\times10^{6} B\bar{B} pairs collected by the Belle experiment and 387\times10^{6} B\bar{B} pairs collected by the Belle II experiment from decays of the \rm Υ(4S) resonance produced in e^{+}e^{-} collisions. A simultaneous fit to the Belle and Belle II data sets yields 11.0^{+6.5}_{-5.5} signal events, corresponding to a 2.5σ significance. We determine the branching fraction \mathcal{B}(B^{0} \to γγ) = (3.7^{+2.2}_{-1.8}(\rm stat)\pm0.5(\rm syst))\times10^{-8} and set a 90% credibility level upper limit of \mathcal{B}(B^{0} \to γγ) < 6.4\times10^{-8}.
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Submitted 27 August, 2024; v1 submitted 30 May, 2024;
originally announced May 2024.
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Measurement of the energy dependence of the e^+e^- \to B\bar{B}, B\bar{B}{}^*, and B^*\bar{B}{}^* cross sections at Belle~II
Authors:
Belle II Collaboration,
I. Adachi,
L. Aggarwal,
H. Ahmed,
H. Aihara,
N. Akopov,
A. Aloisio,
N. Althubiti,
N. Anh Ky,
D. M. Asner,
H. Atmacan,
T. Aushev,
V. Aushev,
M. Aversano,
R. Ayad,
V. Babu,
H. Bae,
S. Bahinipati,
P. Bambade,
Sw. Banerjee,
S. Bansal,
M. Barrett,
J. Baudot,
M. Bauer,
A. Baur
, et al. (444 additional authors not shown)
Abstract:
We report measurements of the e^+e^- \to B\bar{B}, B\bar{B}{}^*, and B^*\bar{B}{}^* cross sections at four energies, 10653, 10701, 10746 and 10805 MeV, using data collected by the Belle~II experiment. We reconstruct one B meson in a large number of hadronic final states and use its momentum to identify the production process. In the first 2-5 MeV above B^*\bar{B}{}^* threshold, the…
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We report measurements of the e^+e^- \to B\bar{B}, B\bar{B}{}^*, and B^*\bar{B}{}^* cross sections at four energies, 10653, 10701, 10746 and 10805 MeV, using data collected by the Belle~II experiment. We reconstruct one B meson in a large number of hadronic final states and use its momentum to identify the production process. In the first 2-5 MeV above B^*\bar{B}{}^* threshold, the e^+e^- \to B^*\bar{B}{}^* cross section increases rapidly. This may indicate the presence of a pole close to the threshold.
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Submitted 4 October, 2024; v1 submitted 29 May, 2024;
originally announced May 2024.
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Test of light-lepton universality in τ decays with the Belle II experiment
Authors:
Belle II Collaboration,
I. Adachi,
K. Adamczyk,
L. Aggarwal,
H. Aihara,
N. Akopov,
A. Aloisio,
N. Anh Ky,
D. M. Asner,
H. Atmacan,
V. Aushev,
M. Aversano,
R. Ayad,
V. Babu,
H. Bae,
S. Bahinipati,
P. Bambade,
Sw. Banerjee,
S. Bansal,
M. Barrett,
J. Baudot,
A. Baur,
A. Beaubien,
F. Becherer,
J. Becker
, et al. (406 additional authors not shown)
Abstract:
We present a measurement of the ratio R_μ= \mathcal{B}(τ^-\to μ^-\barν_μν_τ) / \mathcal{B}(τ^-\to e^-\barν_eν_τ) of branching fractions \mathcal{B} of the τ lepton decaying to muons or electrons using data collected with the Belle II detector at the SuperKEKB e^+e^- collider. The sample has an integrated luminosity of 362\!\pm\!2\,\text{fb}^{-1} at a centre-of-mass energy of…
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We present a measurement of the ratio R_μ= \mathcal{B}(τ^-\to μ^-\barν_μν_τ) / \mathcal{B}(τ^-\to e^-\barν_eν_τ) of branching fractions \mathcal{B} of the τ lepton decaying to muons or electrons using data collected with the Belle II detector at the SuperKEKB e^+e^- collider. The sample has an integrated luminosity of 362\!\pm\!2\,\text{fb}^{-1} at a centre-of-mass energy of 10.58\,\text{GeV}. Using an optimised event selection, a binned maximum likelihood fit is performed using the momentum spectra of the electron and muon candidates. The result, R_μ= 0.9675 \pm 0.0007 \pm 0.0036, where the first uncertainty is statistical and the second is systematic, is the most precise to date. It provides a stringent test of the light-lepton universality, translating to a ratio of the couplings of the muon and electron to the W boson in τ decays of 0.9974 \pm 0.0019, in agreement with the standard model expectation of unity.
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Submitted 30 August, 2024; v1 submitted 23 May, 2024;
originally announced May 2024.
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Search for Two-Body B Meson Decays to Λ^{0} and Ω^{(*)0}_{c}
Authors:
Belle Collaboration,
V. Savinov,
I. Adachi,
J. K. Ahn,
H. Aihara,
D. M. Asner,
H. Atmacan,
R. Ayad,
Sw. Banerjee,
J. Bennett,
M. Bessner,
V. Bhardwaj,
D. Biswas,
A. Bobrov,
D. Bodrov,
J. Borah,
M. Bračko,
P. Branchini,
T. E. Browder,
A. Budano,
D. Červenkov,
M. -C. Chang,
P. Chang,
B. G. Cheon,
K. Cho
, et al. (124 additional authors not shown)
Abstract:
We report the results of the first search for Standard Model and baryon-number-violating two-body decays of the neutral B mesons to Λ^{0} and Ω^{(*)0}_c using 711~{\rm fb^{-1}} of data collected at the Υ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e^+ e^- collider. We observe no evidence of signal from any such decays and set 95\% confidence-level upper limits o…
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We report the results of the first search for Standard Model and baryon-number-violating two-body decays of the neutral B mesons to Λ^{0} and Ω^{(*)0}_c using 711~{\rm fb^{-1}} of data collected at the Υ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e^+ e^- collider. We observe no evidence of signal from any such decays and set 95\% confidence-level upper limits on the products of B^0 and \bar{B}^0 branching fractions for these two-body decays with \mathcal{B}(Ω_{c}^{0} \to π^+ Ω^-) in the range between 9.5~\times 10^{-8} and 31.2~\times 10^{-8}.
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Submitted 18 May, 2024;
originally announced May 2024.
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Characterisation and simulation of stitched CMOS strip sensors
Authors:
Naomi Davis,
Jan-Hendrik Arling,
Marta Baselga,
Leena Diehl,
Jochen Dingfelder,
Ingrid-Maria Gregor,
Marc Hauser,
Fabian Hügging,
Tomasz Hemperek,
Karl Jakobs,
Michael Karagounis,
Roland Koppenhöfer,
Kevin Kröninger,
Fabian Lex,
Ulrich Parzefall,
Arturo Rodriguez,
Birkan Sari,
Niels Sorgenfrei,
Simon Spannagel,
Dennis Sperlich,
Tianyang Wang,
Jens Weingarten,
Iveta Zatocilova
Abstract:
In high-energy physics, there is a need to investigate alternative silicon sensor concepts that offer cost-efficient, large-area coverage. Sensors based on CMOS imaging technology present such a silicon sensor concept for tracking detectors. The CMOS Strips project investigates passive CMOS strip sensors fabricated by LFoundry in a 150nm technology. By employing the technique of stitching, two dif…
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In high-energy physics, there is a need to investigate alternative silicon sensor concepts that offer cost-efficient, large-area coverage. Sensors based on CMOS imaging technology present such a silicon sensor concept for tracking detectors. The CMOS Strips project investigates passive CMOS strip sensors fabricated by LFoundry in a 150nm technology. By employing the technique of stitching, two different strip sensor formats have been realised. The sensor performance is characterised based on measurements at the DESY II Test Beam Facility. The sensor response was simulated utilising Monte Carlo methods and electric fields provided by TCAD device simulations. This study shows that employing the stitching technique does not affect the hit detection efficiency. A first look at the electric field within the sensor and its impact on generated charge carriers is being discussed.
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Submitted 14 May, 2024;
originally announced May 2024.
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Search for lepton-flavor-violating τ^- \to μ^-μ^+μ^- decays at Belle II
Authors:
Belle II Collaboration,
I. Adachi,
L. Aggarwal,
H. Aihara,
N. Akopov,
A. Aloisio,
N. Althubiti,
N. Anh Ky,
D. M. Asner,
H. Atmacan,
V. Aushev,
M. Aversano,
R. Ayad,
V. Babu,
H. Bae,
S. Bahinipati,
P. Bambade,
Sw. Banerjee,
S. Bansal,
M. Barrett,
J. Baudot,
A. Baur,
A. Beaubien,
F. Becherer,
J. Becker
, et al. (407 additional authors not shown)
Abstract:
We present the result of a search for the charged-lepton-flavor violating decay τ^- \to μ^-μ^+μ^- using a 424fb^{-1} sample of data recorded by the Belle II experiment at the SuperKEKB e^{-}e^{+} collider. The selection of e^{-}e^{+}\toτ^+τ^- events is based on an inclusive reconstruction of the non-signal tau decay, and on a boosted decision tree to suppress background. We observe one sig…
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We present the result of a search for the charged-lepton-flavor violating decay τ^- \to μ^-μ^+μ^- using a 424fb^{-1} sample of data recorded by the Belle II experiment at the SuperKEKB e^{-}e^{+} collider. The selection of e^{-}e^{+}\toτ^+τ^- events is based on an inclusive reconstruction of the non-signal tau decay, and on a boosted decision tree to suppress background. We observe one signal candidate, which is compatible with the expectation from background processes. We set a 90\% confidence level upper limit of 1.9 \times 10^{-8} on the branching fraction of the \taumu decay, which is the most stringent bound to date.
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Submitted 28 November, 2024; v1 submitted 12 May, 2024;
originally announced May 2024.
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Determination of the CKM angle φ_{3} from a combination of Belle and Belle II results
Authors:
Belle,
Belle II Collaborations,
:,
I. Adachi,
L. Aggarwal,
H. Aihara,
N. Akopov,
A. Aloisio,
S. Al Said,
N. Anh Ky,
D. M. Asner,
H. Atmacan,
V. Aushev,
M. Aversano,
R. Ayad,
V. Babu,
H. Bae,
S. Bahinipati,
P. Bambade,
Sw. Banerjee,
S. Bansal,
M. Barrett,
J. Baudot,
A. Baur,
A. Beaubien
, et al. (377 additional authors not shown)
Abstract:
We report a determination of the CKM angle φ_{3}, also known as γ, from a combination of measurements using samples of up to 711~fb^{-1} from the Belle experiment and up to 362~fb^{-1} from the Belle II experiment. We combine results from analyses of B^+\to DK^+, B^+\to Dπ^+, and B^+ \to D^{*}K^+ decays, where D is an admixture of D^0 and \overline{D}{}^{0} mesons, in a likelihoo…
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We report a determination of the CKM angle φ_{3}, also known as γ, from a combination of measurements using samples of up to 711~fb^{-1} from the Belle experiment and up to 362~fb^{-1} from the Belle II experiment. We combine results from analyses of B^+\to DK^+, B^+\to Dπ^+, and B^+ \to D^{*}K^+ decays, where D is an admixture of D^0 and \overline{D}{}^{0} mesons, in a likelihood fit to obtain φ_{3} = (78.6^{+7.2}_{-7.3})^{\circ}. We also briefly discuss the interpretation of this result.
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Submitted 12 August, 2024; v1 submitted 19 April, 2024;
originally announced April 2024.
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A beam-driven proton irradiation setup for precision radiation damage tests of silicon detectors
Authors:
Pascal Wolf,
Dennis Sauerland,
Reinhard Beck,
Jochen Dingfelder
Abstract:
A proton irradiation site for silicon detectors has been developed and commissioned at the Bonn Isochronous Cyclotron. The accelerator provides 14 MeV proton beams of up to 1 μA at beam widths of a few mm to the setup. Devices Under Test (DUTs) are irradiated inside a cooled, thermally-insulated box at \le-20°C, while being moved through the beam in a row-based scan pattern to achieve uniform…
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A proton irradiation site for silicon detectors has been developed and commissioned at the Bonn Isochronous Cyclotron. The accelerator provides 14 MeV proton beams of up to 1 μA at beam widths of a few mm to the setup. Devices Under Test (DUTs) are irradiated inside a cooled, thermally-insulated box at \le-20°C, while being moved through the beam in a row-based scan pattern to achieve uniform fluence distributions. Custom-made diagnostics allow for beam-based, on- and offline dosimetry, enabling a beam-driven irradiation routine which produces uniform fluence distributions with standard deviations \ll 1 \% . Dedicated irradiations of thin titanium foils are performed to compare the commonly-used dosimetry via metallic foil activation to the beam-based approach. Within the error margins, both methods are in agreement, whereas the beam-based technique yields lower uncertainties of typically \le 2 \% . Simulations indicate a reduction of the initial proton energy to 12.28(6) MeV on the DUT. Characterization of six, 150 μm-thin, passive LFoundry sensors before and after irradiation yield a proton hardness factor of κ_\text{p}=3.71(11), which is in agreement with expectations, allowing to irradiate up to 10^{16} \text{n}_{eq} / \text{cm}^2 within a few hours.
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Submitted 5 May, 2024; v1 submitted 17 April, 2024;
originally announced April 2024.
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Measurement of the branching fraction of the decay B^- \to D^0 ρ(770)^- at Belle II
Authors:
Belle II Collaboration,
I. Adachi,
L. Aggarwal,
H. Aihara,
N. Akopov,
A. Aloisio,
N. Anh Ky,
D. M. Asner,
H. Atmacan,
V. Aushev,
M. Aversano,
R. Ayad,
V. Babu,
H. Bae,
S. Bahinipati,
P. Bambade,
Sw. Banerjee,
S. Bansal,
M. Barrett,
J. Baudot,
A. Baur,
A. Beaubien,
F. Becherer,
J. Becker,
J. V. Bennett
, et al. (367 additional authors not shown)
Abstract:
We measure the branching fraction of the decay B^- \to D^0 ρ(770)^- using data collected with the Belle II detector. The data contain 387 million B\overline{B} pairs produced in e^+e^- collisions at the Υ(4S) resonance. We reconstruct 8360\pm 180 decays from an analysis of the distributions of the B^- energy and the ρ(770)^- helicity angle. We determine the branching fraction to be…
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We measure the branching fraction of the decay B^- \to D^0 ρ(770)^- using data collected with the Belle II detector. The data contain 387 million B\overline{B} pairs produced in e^+e^- collisions at the Υ(4S) resonance. We reconstruct 8360\pm 180 decays from an analysis of the distributions of the B^- energy and the ρ(770)^- helicity angle. We determine the branching fraction to be (0.939 \pm 0.021\mathrm{(stat)} \pm 0.050\mathrm{(syst)})\%, in agreement with previous results. Our measurement improves the relative precision of the world average by more than a factor of two.
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Submitted 27 June, 2024; v1 submitted 16 April, 2024;
originally announced April 2024.
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Search for Rare b \to d\ell^+\ell^- Transitions at Belle
Authors:
Belle,
Belle II Collaborations,
:,
I. Adachi,
L. Aggarwal,
H. Aihara,
N. Akopov,
A. Aloisio,
S. Al Said,
D. M. Asner,
H. Atmacan,
V. Aushev,
M. Aversano,
R. Ayad,
V. Babu,
H. Bae,
S. Bahinipati,
P. Bambade,
Sw. Banerjee,
S. Bansal,
M. Barrett,
J. Baudot,
A. Beaubien,
F. Becherer,
J. Becker
, et al. (371 additional authors not shown)
Abstract:
We present the results of a search for the b \to d\ell^+\ell^- flavor-changing neutral-current rare decays B^{+, 0} \to (η, ω, π^{+,0}, ρ^{+, 0}) e^+e^- and B^{+, 0} \to (η, ω, π^{0}, ρ^{+}) μ^+μ^- using a 711 fb^{-1} data sample that contains 772 \times 10^{6} B\overline{B} events. The data were collected at the Υ(4S) resonance with the Belle detector at the KEKB asymmetric-energy…
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We present the results of a search for the b \to d\ell^+\ell^- flavor-changing neutral-current rare decays B^{+, 0} \to (η, ω, π^{+,0}, ρ^{+, 0}) e^+e^- and B^{+, 0} \to (η, ω, π^{0}, ρ^{+}) μ^+μ^- using a 711 fb^{-1} data sample that contains 772 \times 10^{6} B\overline{B} events. The data were collected at the Υ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e^+e^- collider. We find no evidence for signal and set upper limits on branching fractions at the 90\% confidence level in the range (3.8 - 47) \times 10^{-8} depending on the decay channel. The obtained limits are the world's best results. This is the first search for the channels B^{+, 0} \to (ω, ρ^{+,0}) e^+e^- and B^{+, 0} \to (ω, ρ^{+})μ^+μ^-.
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Submitted 6 September, 2024; v1 submitted 11 April, 2024;
originally announced April 2024.
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Measurement of the e^+e^- \to π^+π^-π^0 cross section in the energy range 0.62-3.50 GeV at Belle II
Authors:
Belle II Collaboration,
I. Adachi,
L. Aggarwal,
H. Aihara,
N. Akopov,
A. Aloisio,
N. Anh Ky,
D. M. Asner,
H. Atmacan,
V. Aushev,
M. Aversano,
R. Ayad,
V. Babu,
H. Bae,
S. Bahinipati,
P. Bambade,
Sw. Banerjee,
S. Bansal,
M. Barrett,
J. Baudot,
A. Baur,
A. Beaubien,
F. Becherer,
J. Becker,
J. V. Bennett
, et al. (338 additional authors not shown)
Abstract:
We report a measurement of the e^+e^- \to π^+π^-π^0 cross section in the energy range from 0.62 to 3.50 GeV using an initial-state radiation technique. We use an e^+e^- data sample corresponding to 191 \text{fb}^{-1} of integrated luminosity, collected at a center-of-mass energy at or near the Υ{(4S)} resonance with the Belle II detector at the SuperKEKB collider. Signal yields are extract…
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We report a measurement of the e^+e^- \to π^+π^-π^0 cross section in the energy range from 0.62 to 3.50 GeV using an initial-state radiation technique. We use an e^+e^- data sample corresponding to 191 \text{fb}^{-1} of integrated luminosity, collected at a center-of-mass energy at or near the Υ{(4S)} resonance with the Belle II detector at the SuperKEKB collider. Signal yields are extracted by fitting the two-photon mass distribution in e^+e^- \to π^+π^-π^0γ events, which involve a π^0 \to γγ decay and an energetic photon radiated from the initial state. Signal efficiency corrections with an accuracy of 1.6% are obtained from several control data samples. The uncertainty on the cross section at the ω and φ resonances is dominated by the systematic uncertainty of 2.2%. The resulting cross sections in the 0.62-1.80 GeV energy range yield a_μ^{3π} = [48.91 \pm 0.23~(\mathrm{stat}) \pm 1.07~(\mathrm{syst})] \times 10^{-10} for the leading-order hadronic vacuum polarization contribution to the muon anomalous magnetic moment. This result differs by 2.5 standard deviations from the most precise current determination.
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Submitted 8 December, 2024; v1 submitted 7 April, 2024;
originally announced April 2024.
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Angular analysis of B \to K^* e^+ e^- in the low-q^2 region with new electron identification at Belle
Authors:
Belle Collaboration,
D. Ferlewicz,
P. Urquijo,
I. Adachi,
K. Adamczyk,
H. Aihara,
D. M. Asner,
H. Atmacan,
R. Ayad,
V. Babu,
Sw. Banerjee,
P. Behera,
K. Belous,
J. Bennett,
M. Bessner,
V. Bhardwaj,
B. Bhuyan,
T. Bilka,
D. Biswas,
D. Bodrov,
M. Bračko,
P. Branchini,
T. E. Browder,
A. Budano,
M. Campajola
, et al. (145 additional authors not shown)
Abstract:
We perform an angular analysis of the B\to K^* e^+ e^- decay for the dielectron mass squared, q^2, range of 0.0008 to 1.1200 ~\text{GeV}^2 /c^4 using the full Belle data set in the K^{*0} \to K^+ π^- and K^{*+} \to K_S^0 π^+ channels, incorporating new methods of electron identification to improve the statistical power of the data set. This analysis is sensitive to contributions from r…
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We perform an angular analysis of the B\to K^* e^+ e^- decay for the dielectron mass squared, q^2, range of 0.0008 to 1.1200 ~\text{GeV}^2 /c^4 using the full Belle data set in the K^{*0} \to K^+ π^- and K^{*+} \to K_S^0 π^+ channels, incorporating new methods of electron identification to improve the statistical power of the data set. This analysis is sensitive to contributions from right-handed currents from physics beyond the Standard Model by constraining the Wilson coefficients \mathcal{C}_7^{(\prime)}. We perform a fit to the B\to K^* e^+ e^- differential decay rate and measure the imaginary component of the transversality amplitude to be A_T^{\rm Im} = -1.27 \pm 0.52 \pm 0.12, and the K^* transverse asymmetry to be A_T^{(2)} = 0.52 \pm 0.53 \pm 0.11, with F_L and A_T^{\rm Re} fixed to the Standard Model values. The resulting constraints on the value of \mathcal{C}_7^{\prime} are consistent with the Standard Model within a 2σ confidence interval.
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Submitted 11 September, 2024; v1 submitted 29 March, 2024;
originally announced April 2024.
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Search for a pentaquark state decaying into pJ/ψ in Υ(1,2S) inclusive decays at Belle
Authors:
Belle Collaboration,
X. Dong,
H. Y. Zhang,
X. L. Wang,
I. Adachi,
J. K. Ahn,
H. Aihara,
S. Al Said,
D. M. Asner,
H. Atmacan,
R. Ayad,
S. Bahinipati,
Sw. Banerjee,
M. Bessner,
V. Bhardwaj,
D. Biswas,
D. Bodrov,
A. Bozek,
M. Bračko,
P. Branchini,
T. E. Browder,
A. Budano,
M. Campajola,
D. Červenkov,
M. -C. Chang
, et al. (139 additional authors not shown)
Abstract:
Using the data samples of 102 million Υ(1S) and 158 million Υ(2S) events collected by the Belle detector, we search for a pentaquark state in the pJ/ψ final state from Υ(1,2S) inclusive decays. Here, the charge-conjugate \bar{p}J/ψ is included. We observe clear pJ/ψ production in Υ(1,2S) decays and measure the branching fractions to be…
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Using the data samples of 102 million Υ(1S) and 158 million Υ(2S) events collected by the Belle detector, we search for a pentaquark state in the pJ/ψ final state from Υ(1,2S) inclusive decays. Here, the charge-conjugate \bar{p}J/ψ is included. We observe clear pJ/ψ production in Υ(1,2S) decays and measure the branching fractions to be B[Υ(1S) \to pJ/ψ+ anything] = [4.31 \pm 0.16(stat.) \pm 0.19(syst.)] \times 10^{-5} and B[Υ(2S) \to pJ/ψ+ anything] = [2.31 \pm 0.15(stat.) \pm 0.16(syst.)] \times 10^{-5}. We also measure the cross section of inclusive pJ/ψ production in e^+e^- annihilation to be σ(e^+e^- \to pJ/ψ+ anything) = [58.5 \pm 2.1 (stat.) \pm 2.7(syst.)]~fb at \sqrt{s} = 10.52~\hbox{GeV} using an 89.5~fb^{-1} continuum data sample. There is no significant P_c(4312)^+, P_c(4440)^+ or P_c(4457)^+ signal found in the pJ/ψ final states in Υ(1,2S) inclusive decays. We determine the upper limits of B[Υ(1,2S)\to P_c^{+} + anything] \cdot B(P_c^{+}\to pJ/ψ) to be at the 10^{-6} level.
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Submitted 20 March, 2025; v1 submitted 7 March, 2024;
originally announced March 2024.
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Search for a μ^+μ^- resonance in four-muon final states at Belle II
Authors:
Belle II Collaboration,
I. Adachi,
K. Adamczyk,
L. Aggarwal,
H. Ahmed,
H. Aihara,
N. Akopov,
A. Aloisio,
N. Anh Ky,
D. M. Asner,
H. Atmacan,
V. Aushev,
M. Aversano,
R. Ayad,
V. Babu,
H. Bae,
S. Bahinipati,
P. Bambade,
Sw. Banerjee,
S. Bansal,
M. Barrett,
J. Baudot,
A. Baur,
A. Beaubien,
F. Becherer
, et al. (379 additional authors not shown)
Abstract:
We report on a search for a resonance X decaying to a pair of muons in e^{+}e^{-}\rightarrow μ^+ μ^- X events in the 0.212-9.000 GeV/c^{2} mass range, using 178 fb^{-1} of data collected by the BelleII experiment at the SuperKEKB collider at a center of mass energy of 10.58 GeV. The analysis probes two different models of X beyond the standard model: a Z^{\prime} vector boson in the…
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We report on a search for a resonance X decaying to a pair of muons in e^{+}e^{-}\rightarrow μ^+ μ^- X events in the 0.212-9.000 GeV/c^{2} mass range, using 178 fb^{-1} of data collected by the BelleII experiment at the SuperKEKB collider at a center of mass energy of 10.58 GeV. The analysis probes two different models of X beyond the standard model: a Z^{\prime} vector boson in the L_μ-L_τ model and a muonphilic scalar. We observe no evidence for a signal and set exclusion limits at the 90\% confidence level on the products of cross section and branching fraction for these processes, ranging from 0.046 fb to 0.97 fb for the L_μ-L_τ model and from 0.055 fb to 1.3 fb for the muonphilic scalar model. For masses below 6 GeV/c^{2}, the corresponding constraints on the couplings of these processes to the standard model range from 0.0008 to 0.039 for the L_μ-L_τ model and from 0.0018 to 0.040 for the muonphilic scalar model. These are the first constraints on the muonphilic scalar from a dedicated search.
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Submitted 26 June, 2024; v1 submitted 5 March, 2024;
originally announced March 2024.
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Measurement of CP asymmetries in B^0 \rightarrow K^0_S K^0_S K^0_S decays at Belle II
Authors:
Belle II Collaboration,
I. Adachi,
L. Aggarwal,
H. Ahmed,
H. Aihara,
N. Akopov,
A. Aloisio,
N. Anh Ky,
D. M. Asner,
H. Atmacan,
T. Aushev,
V. Aushev,
M. Aversano,
R. Ayad,
V. Babu,
H. Bae,
S. Bahinipati,
P. Bambade,
Sw. Banerjee,
S. Bansal,
M. Barrett,
J. Baudot,
M. Bauer,
A. Baur,
A. Beaubien
, et al. (428 additional authors not shown)
Abstract:
We report a measurement of decay-time dependent charge-parity (CP) asymmetries in B^0 \rightarrow K^0_S K^0_S K^0_S decays. We use 387 \times 10^6 B\bar{B} pairs collected at the Υ(4S) resonance with the Belle II detector at the SuperKEKB asymmetric-energy electron-positron collider. We reconstruct 220 signal events and extract the CP-violating parameters S and C from a fit to the di…
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We report a measurement of decay-time dependent charge-parity (CP) asymmetries in B^0 \rightarrow K^0_S K^0_S K^0_S decays. We use 387 \times 10^6 B\bar{B} pairs collected at the Υ(4S) resonance with the Belle II detector at the SuperKEKB asymmetric-energy electron-positron collider. We reconstruct 220 signal events and extract the CP-violating parameters S and C from a fit to the distribution of the decay-time difference between the two B mesons. The resulting confidence region is consistent with previous measurements in B^0 \rightarrow K^0_S K^0_S K^0_S and B^0 \rightarrow (c\bar{c})K^0 decays, and with predictions based on the standard model.
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Submitted 4 March, 2024;
originally announced March 2024.
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Cross talk of a large-scale depleted monolithic active pixel sensor (DMAPS) in 180 nm CMOS technology
Authors:
Lars Schall,
Christian Bespin,
Ivan Caicedo,
Jochen Dingfelder,
Tomasz Hemperek,
Toko Hirono,
Fabian Hügging,
Hans Krüger,
Konstantinos Moustakas,
Heinz Pernegger,
Petra Riedler,
Walter Snoeys,
Norbert Wermes,
Sinuo Zhang
Abstract:
Monolithic pixel detectors combine readout electronics and sensor in a single entity of silicon, which simplifies the production procedure and lowers the material budget compared to conventional hybrid pixel detector concepts. Benefiting from the advances in commercial CMOS processes towards large biasing voltage capabilities and the increasing availability of high-resistivity substrates, depleted…
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Monolithic pixel detectors combine readout electronics and sensor in a single entity of silicon, which simplifies the production procedure and lowers the material budget compared to conventional hybrid pixel detector concepts. Benefiting from the advances in commercial CMOS processes towards large biasing voltage capabilities and the increasing availability of high-resistivity substrates, depleted monolithic active pixel sensors (DMAPS) are able to cope with the high-rate and high-radiation environments faced in modern high-energy physics experiments. TJ-Monopix2 is the latest iteration of a DMAPS development line designed in 180 nm TowerSemicondutor technology, which features a large scale (2 x 2) cm^2 chip divided into (512 x 512) pixels with a pitch of (33 x 33) um^2. All in-pixel electronics are separated from its small collection electrode and process modifications are implemented to improve charge collection efficiency especially after irradiation. The latest laboratory measurements and investigations of a threshold variation observed for TJ-Monopix2 in typical operating conditions are presented.
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Submitted 19 February, 2024;
originally announced February 2024.