Resurgence of $Z^{\prime }$ from the single electron-muon event at ATLAS

Abstract

Inspired by the recent single $e^{\pm }{\mu }^{\mp }$ event at 2.1 TeV invariant mass from the ATLAS at $\sqrt{s}=13$ TeV with 3.2 fb${}^{-1}$ luminosity, we propose an explanation using a $Z^{\prime }$ gauge boson, which possesses lepton-flavor-changing neutral currents originated from non-universal couplings to charged leptons. We assume that the left-handed charged-lepton mixing matrix equals to the PMNS matrix and no mixing in the neutrino sector to make this phenomenological $Z^{\prime }$ model more predictive. There are indeed some parameter regions, where the $Z^{\prime }$ can generate a large enough $e^{\pm }{\mu }^{\mp }$ production cross section, while at the same time satisfies various observables from lepton-flavor violation and other constraints from the LHC.

Comments: 14 pages, 1 table, 1 figure