Measurement of the associated production of a Z boson with charm or bottom quark jets in proton-proton collisions at √s = 13 TeV

Abstract

Ratios of cross sections, σ(Z+c jets )/σ ( Z+ jets), σ( Z+b jets )/ σ( Z+ jets), and σ(Z+c jets )/σ(Z+b jets) in the associated production of a Z boson with at least one charm or bottom quark jet are measured in proton-proton collisions at √s=13 TeV. The data sample, collected by the CMS experiment at the CERN LHC, corresponds to an integrated luminosity of 35.9 fb − 1 , with a fiducial volume of p T > 30 GeV and | η | < 2.4 for the jets, where p T and η represent transverse momentum and pseudorapidity, respectively. The Z boson candidates come from leptonic decays into electrons or muons with p T > 25 GeV and | η | < 2.4 , and the dilepton mass satisfies 71 < m Z < 111 GeV . The measured values are σ ( Z + c jets ) / σ ( Z + jets ) = 0.102 ± 0.002 ± 0.009 , σ ( Z + b jets ) / σ ( Z + jets ) = 0.0633 ± 0.0004 ± 0.0015 , and σ ( Z + c jets ) / σ ( Z + b jets ) = 1.62 ± 0.03 ± 0.15 . Results on the inclusive and differential cross section ratios as functions of jet and Z boson transverse momentum are compared with predictions from leading and next-to-leading order perturbative quantum chromodynamics calculations. These are the first measurements of the cross section ratios at 13 TeV.