Non Perturbative Quantum Chromo Dynamics

While we all believe that Quantum Chromodynamics is the correct theory for describing the strong force, reliable predictions can only be made for high-energy processes where the strong coupling constant is small. Nevertheless, there exists a rich phenomenology of low-energy QCD processes that could provide valuable insights into describing the strong force in close proximity to confinement. We investigate these non-perturbative QCD effects at the ATLAS Experiment, utilizing both proton-proton and heavy ion collisions.

Searches for QCD Instantons

People typically do not know, but QCD predicts a non trivial structure of the vacuum and allows in principle for transitions between two neighbouring vacuum states. Those transitions are known as Instantons. While those effects are predicted by the theory, nobody ever observed a direct evidence of Instanton processes. We have co-developed first tools to search for such effects at the LHC and are currently investigating several approaches to find a direct evidence in data

QCD Instantons
© Ismail Zahed
Eine Wissenschaftlerin und ein Wissenschaftler arbeiten hinter einer Glasfassade und mischen Chemikalien mit Großgeräten.

Heavy Ion Physics

Not only proton-proton collisions are from interest at the LHC, but also heavy ion collisions. Those collisions recreate really conditions closely after the Big Bang since a quark-gluon plasma is formed. We are interested in studying top-quark production in heavy ion collisions as well as searches for the chiral magnetic effect.

Diffractive Physics

W and Z bosons can not only be produced in hard-collision events at the LHC, but also by so-called diffractive processes induced by "Pomeron" exchanges. While those processes only contribute at percent level to the full production process of vector bosons, their correct modelling might be crucial for electroweak precision measurements.

© Royon Christophe
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