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Title: Measuring charge asymmetries in b-hadron decays using top quark events with the ATLAS experiment
Author: D'Onofrio, Adelina
ISNI:       0000 0004 7966 6314
Awarding Body: Queen Mary University of London
Current Institution: Queen Mary, University of London
Date of Award: 2019
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The large number of top-antitop pair events produced in pp collisions at the Large Hadron Collider (LHC) provides a unique source of b-quarks that can be used to probe the CP violation in heavy-flavour mixing and decay. The measurement presented in this thesis focuses on semi-leptonic top-antitop events where one of the W-bosons decays hadronically and the other one decays leptonically. The charge of the lepton (electron or muon) from the W-boson tags the charge of the b-quark at production. In events where a muon is associated to the semi-leptonic decay of the b-quark (either directly or after a b ! c hadronic transition), two charge asymmetries (CA) and several CP asymmetries, based on the charges of the lepton from the W-boson and this muon, can be measured. My contribution to the first measurement of the CA and CP asymmetries in heavy flavour b- or c-decays from top-antitop lepton+jets events is presented, using the data collected with the ATLAS detector during Run 1 of the LHC (20.3 fb 1) at a centre of mass energy of p s = 8 TeV. However, most of the thesis focuses on my (larger) contribution to this same measurement, performed with data collected by the ATLAS experiment during Run 2, 2015-16 data taking periods, corresponding to an integrated luminosity of 36.1 fb 1 at a centre of mass energy of p s = 13 TeV. Four CP asymmetries (one mixing and three direct) were measured, using Run 1 data, and they are found to be consistent with the Standard Model. The Run 2 analysis results in the measurement of two charge asymmetries, both compatible with zero and consistent with the Standard Model expectations. The overall uncertainty on the Run 2 measurement is halved with respect to the Run 1 result.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Physics and astronomy ; Large Hadron Collider ; semi-leptonic top-antitop events ; particle physics