Stringent Dilepton Bounds on Left-Right Models using LHC data

TL;DR

This paper uses LHC 8 TeV dilepton data to set new lower bounds on the $Z_R$ gauge boson mass in left-right symmetric models, excluding masses up to about 3.2 TeV, with implications for model parameter space.

Contribution

It provides the first robust collider bounds on the $Z_R$ mass in non-canonical left-right models using dilepton data, independent of right-handed neutrino masses.

Findings

Excluded $Z_R$ masses up to ~3.2 TeV for various couplings.

Set a lower bound of ~2.5 TeV for the canonical left-right model.

Bounds are nearly independent of right-handed neutrino masses.

Abstract

In canonical left-right symmetric models the lower mass bounds on the charged gauge bosons are in the ballpark of $3-4$ TeV, resulting into much stronger limits on the neutral gauge boson $Z_R$, making its production unreachable at the LHC. However, if one evokes different patterns of left-right symmetry breaking the $Z_R$ might be lighter than the $W_R^\pm$ motivating an independent $Z_R$ collider study. In this work, we use the 8 TeV ATLAS $20.3$ fb$^{-1}$ luminosity data to derive robust bounds on the $Z_R$ mass using dilepton data. %because they provide the most restrictive limits due to the sizable $Z_R$-lepton couplings. We find strong lower bounds on the $Z_R$ mass for different right-handed gauge couplings, excluding $Z_R$ masses up to $\sim 3.2$TeV. For the canonical LR model we place a lower mass bound of $\sim 2.5$TeV. Our findings are almost independent of the right-handed neutrino masses ($\sim 2\,\%$ effect) and applicable to general left-right models.