Measurement of the production cross section for Z + b jets in proton-proton collisions at $\sqrt{s} =$ 13 TeV

TL;DR

This paper reports a precise measurement of the Z boson production cross section with bottom quark jets in proton-proton collisions at 13 TeV, testing quantum chromodynamics predictions.

Contribution

It provides the first detailed measurement of Z + b jets cross sections at 13 TeV, including differential distributions and ratios, with high precision and comparison to theoretical models.

Findings

Measured integrated cross sections for Z + ≥1 b jet and Z + ≥2 b jets.

Determined ratios of cross sections for different b jet multiplicities.

Compared measurements with various event generator predictions.

Abstract

The measurement of the cross section for the production of a Z boson, decaying to dielectrons or dimuons, in association with at least one bottom quark jet are performed with proton-proton collision data at $\sqrt{s} =$ 13 TeV. The data sample corresponds to an integrated luminosity of 137 fb$^{-1}$, collected by the CMS experiment at the LHC during 2016-2018. The integrated cross sections for Z + $\ge$ 1 b jet and Z + $\ge$ 2 b jets are reported for the electron, muon, and combined channels. The fiducial cross sections in the combined channel are 6.52 $\pm$ 0.04 (stat) $\pm$ 0.40 (syst) $\pm$ 0.14 (theo) pb for Z + $\ge$ 1 b jet and 0.65 $\pm$ 0.03 (stat) $\pm$ 0.07 (syst) $\pm$ 0.02 (theo) pb for Z + $\ge$ 2 b jets. The differential cross section distributions are measured as functions of various kinematic observables that are useful for precision tests of perturbative quantum chromodynamics predictions. The ratios of integrated and differential cross sections for Z + $\ge$ 2 b jets and Z + $\ge$ 1 b jet processes are also determined. The value of the integrated cross section ratio measured in the combined channel is 0.100 $\pm$ 0.005 (stat) $\pm$ 0.007 (syst) $\pm$ 0.003 (theo). All measurements are compared with predictions from various event generators.