Measurement of charm and beauty quark production cross sections with the CMS Experiment at the LHC at a center of mass energy of 5 TeV

This thesis presents measurements of charm and beauty quark production in proton–proton collisions at a center-of-mass energy of √s = 5 TeV using the CMS detector at the LargeHadron Collider at CERN.Heavy-flavor production cross sections test perturbative Quantum Chromodynamics and constrain parameters such as heavy-quark masses and the proton parton distribution functions.In this work, the double-differential production cross sections of D∗ mesons are measured as functions of the transverse momentum pT and the absolute rapidity |y|, reaching very low transverse momenta. The kinematic region covered by CMS is complementary to previous measurements at the LHC. The reconstructed D∗ mesons originate either from prompt charm-quark hadronization or from decays of beauty hadrons. Because of the longer lifetime of beauty hadrons, these contributions can be statistically separated using lifetime-sensitive observables, enabling separate measurements of charm and beauty production cross sections. The systematic uncertainties are evaluated, and the results are compared to perturbative QCD predictions and to previous measurements by the LHCb, ALICE, and CMS experiments. In addition, the measured fiducial cross sections are used for a simplified Monte Carlo based preliminary extrapolation to the total heavy-quark pair production cross sections, yielding σc ¯ c ≈ 8 mb and σb¯b ≈ 0.4 mb. The charm pair production result is compatible with previous extrapolations based on ALICE and LHCb measurements and with QCD predictions within sizable uncertainties.