Measurements of the differential cross sections of the production of Z + jets and $\gamma$ + jets and of Z boson emission collinear with a jet in pp collisions at $\sqrt{s} =$ 13 TeV

TL;DR

This paper presents detailed measurements of Z + jets and gamma + jets production cross sections at 13 TeV, including their ratio and angular distributions, providing new insights and comparisons with theoretical models at the LHC.

Contribution

It reports the first measurement of the ratio of Z + jets to gamma + jets cross sections and the first direct measurement of Z bosons emitted collinearly with a jet at 13 TeV.

Findings

Higher-order theoretical predictions agree better with measurements.

The ratio of Z + jets to gamma + jets cross sections is measured for the first time at 13 TeV.

Angular distributions between Z bosons and jets are characterized.

Abstract

Measurements of the differential cross sections of Z + jets and $\gamma$ + jets production, and their ratio, are presented as a function of the boson transverse momentum. Measurements are also presented of the angular distribution between the Z boson and the closest jet. The analysis is based on pp collisions at a center-of-mass energy of 13 TeV corresponding to an integrated luminosity of 35.9 fb$^{-1}$ recorded by the CMS experiment at the LHC. The results, corrected for detector effects, are compared with various theoretical predictions. In general, the predictions at higher orders in perturbation theory show better agreement with the measurements. This work provides the first measurement of the ratio of the differential cross sections of Z + jets and $\gamma$ + jets production at 13 TeV, as well as the first direct measurement of Z bosons emitted collinearly with a jet.