Precision Physics

The Standard Model of particle physics enables precise predictions for several of its observables. For instance, by knowing the mass of the Z boson, the top quark, and the Higgs boson, as well as the electroweak mixing angle and the fine structure constant, one can predict the mass of the W boson. If significant disparities arise between the predicted and measured values of the W boson mass, it would suggest an issue with the Standard Model—essentially indicating the observation of indirect effects stemming from unknown (new) physics.

Measurement of the W Boson Mass

The measurement of the W boson mass was the starting project of our research group in 2012, where we aimed at an uncertainty of 10 MeV. In 2016 we published the first precision measurement at the LHC with an uncertainty of 19 MeV, being the most precise measurement up to date. Until 2023, we worked on an improved measurement using the same data-set but advance statistical models, allowing us to reduce the uncertainty to 16 MeV. We are currently working on a new data-set, hopefully realising a measurement at 10 MeV level.

W Boson Mass
© ATLAS Collaboration
Eine Wissenschaftlerin und ein Wissenschaftler arbeiten hinter einer Glasfassade und mischen Chemikalien mit Großgeräten.
© Matthias Schott, Stefano Camarda

Measurement of the Strong Coupling Constant

As a side-project of the W boson mass measurement, we co-developed a new MC generator program, named DYTURBO, which allows for a high precision calculation of the transverse momentum spectrum of the Z boson, pT(Z). It turned out that the predicted spectrum is highly sensitive on the strong coupling constant. Hence a precise measurement of pT(Z) can be in turn be used to determine the strong coupling constant. We published this idea in 2022 with a first determination using published data by CDF. This was followed by a dedicated measurement by the ATLAS Collaboration using data at a center of mass energy of 8 TeV. We are currently aiming at new measurement using newer data as well as including dedicated support measurements.

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