Studies of Z $\to$ 4$\ell$ decays in proton-proton collisions at $\sqrt{s}$ = 8 and 13 TeV

Abstract

Decays of Z bosons to four charged leptons (electrons and muons) are studied in proton-proton collisions at $\sqrt{s}$ = 8 and 13 TeV. The analysis is based on data collected with the CMS detector at the LHC corresponding to an integrated luminosity of 19.7 fb${}^{-1}$ at 8 TeV and 138 fb${}^{-1}$ at 13 TeV. The measured value of the inclusive branching fraction for all four-lepton decay modes, $\mathcal{B}$(Z $\to$ 4$\ell$), is [4.67 $\pm$ 0.11 (stat) $\pm$ 0.10 (syst)] $\times$ 10${}^{-6}$, which has a precision of about 3% limited by both statistical and systematic uncertainties. Measurements of the individual branching fractions for the decays Z $\to$ 4$\mu$, Z $\to$ 4e, and Z $\to$ 2$\mu$2e are also reported. Differential decay rates are presented as functions of kinematic and angular quantities in the Z boson rest frame. Measurements of triple-product asymmetries, which are sensitive to possible violations of charge conjugation and parity invariance, are performed for Z $\to$ 4$\ell$ decays. The results are compared with standard model predictions and used to set limits on the production of new gauge bosons.

arXiv commentSubmitted to Physical Review D. All figures and tables can be found at http://cms-results.web.cern.ch/cms-results/public-results/publications/SMP-19-007 (CMS Public Pages)