Seminario di Fenomenologia – Dr. Alessandro Guida (Genova Univ. and DESY Hamburg)
High energy physics experiments are performed at the Large Hadron Collider at CERN colliding bunches of protons at energies up to 13 TeV. The ATLAS experiment, with its multipurpose detector, studies the products of these colli- sions and compares the experimental measurements with the predictions of the Standard Model. This talk presents the study of the process Z/γ∗ → μμ at low invariant mass of the di-muon pair, in the region between 7 GeV and 60 GeV, below the Z boson resonance mass peak (mZ = 91.2 GeV). The single and double differential cross sections of the process are measured in 13 TeV proton-proton collisions at the LHC, using the ATLAS detector. The measurement explores an extreme region of the phase space and is sensitive to resummation results in the theoretical prediction. The analysis exploits the good resolution of the ATLAS detector in reconstructing low momentum muons. The main difficulties come instead from the high background component that enters in the event selection, the triggering of events and the modelling of some key physical quantities.The main features of the analysis, the studies done to overcome the main challenges, as well as the first results and comparison to theory predictions are presented in the talk.
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