Measurement of b-jet to inclusive jet ratio in PbPb and pp collisions at s=2.76 TeV with the CMS detector

Abstract

AbstractModification to jets in high-energy heavy–ion collisions is expected to depend on the flavor of the fragmenting parton. To disentangle this flavor dependence, jets from heavy quark fragmentation are identified for the first time in heavy–ion collisions. Jets are first tagged by their secondary vertices and the contribution from bottom quarks is extracted using template fits to their secondary mass distribution. The bottom quark jet to inclusive jet ratio is measured with the CMS detector in PbPb and pp collisions at a center-of-mass energy of 2.76 TeV per nucleon. The b-jet fraction is measured in the range of 80<jet pT<200 GeV/c in PbPb collisions and found to lie in the range of 2.9–3.5% ± 0.6–1.1% depending on jet pT. The measured values for PbPb and pp are comparable, within uncertainties, to those predicted by simulation. The measurement is a promising method to study b-quark energy loss. Improved statistics should allow to make a more precise comparison between light and b-quark quenching