Measurement of the production cross section of heavy quark jets in association with a W boson with the ATLAS detector at the LHC

In this thesis the production of a W boson in association with heavy-quark jets has been studied in proton-proton collisions at a centre-of-mass energy of 7 TeV with the ATLAS detector at the Large Hadron Collider (LHC). For the identification of the W bosons and of the heavy quarks their semileptonic decays have been used. For this purpose, detailed studies of the muon reconstruction efficiencies of the ATLAS detector have been performed. The associated production of a W boson with bottom quark jets represents an important background for searches for the Higgs boson and beyond Standard Model physics. It is therefore important to verify experimentally the Standard Model predictions for this process in the new energy regime of the LHC. The cross sections for W boson production together with a b-jet and zero or one additional jet have been measured for the first time at LHC energies and were found to be consistent with next-to-leading order QCD predictions. The W boson production in association with a charm quark jet is of particular interest because of the sensitivity to the strange quark content of the proton which is still rather poorly constrained by experiments. The cross section measurements for this process in this thesis are an important input for the determination of the strange quark parton density function in the energy regime of the LHC.