Speaker
Description
With the 13 TeV proton-proton collisions measured by the CMS detector at the LHC, a detailed measurement of the Z+jet production provides ideal conditions for the hadronic jet production study, which provides a stringent test for perturbative QCD. It also helps to understand the non-perturbative QCD models by reflecting the soft-gluon emission kinematics in the low Z pt region. The differential cross sections of the Z(l+l-)+jets are measured as a function of jet multiplicity in various Z pT regions. The azimuthal correlation between the Z boson and the leading jet as well as that between the two leading jets are also measured for different Z pT. The measurements are compared to various theoretical predictions to evaluate the matrix
+element caluculation, the parton density models and the multi-parton interaction (MPI) effects.
On the MC tuning side, two color reconnection models, QCD-inspired and gluon-move are implemented to the PYTHIA8 generator. New sets of parameters are obtained by tuning the parameters of the color reconnection models and multi-parton interactions simultaneously to the 1.96, 7 and 13 TeV measurements that are sensitive to underlying event (UE) contributions. The predictions of the new tunings are compared for observables in various processes, including the minimum bias observables, the strange baryon particle multiplicity, the jet substructure, the Drell-Yan kinematics and UE activity and jet structures in top pair productions.
