Constraints on $U(1{)}_{L_{\mu }-L_{\tau }}$ from LHC Data

Abstract

In this study, we apply LHC data to constrain the extension of the Standard Model by an anomaly-free $U(1{)}_{L_{\mu }-L_{\tau }}$ gauge group; this model contains a new gauge boson ($Z^{\prime }$) and a scalar dark matter particle (${\varphi }_{\mathrm{DM}}$). We recast a large number of LHC analyses from ATLAS and CMS of multi-lepton final states. We find that for $10$ GeV $<m_{Z^{\prime }}<60$ GeV the strongest constraint comes from a dedicated $Z^{\prime }$ search in the $4\mu$ final state by the CMS collaboration; for larger $Z^{\prime }$ masses, searches for final states with three leptons plus missing $E_T$ are more sensitive. Searches for final states with two leptons and missing $E_T$, which are sensitive to $Z^{\prime }$ decays into dark matter particles, can only probe regions of parameter space that are excluded by searches in the $3$ and $4$ lepton channels. The combination of LHC data excludes values of $Z^{\prime }$ mass and coupling constant that can explain the deficit in $g_{\mu }-2$ for $4$ GeV $\le m_{Z^{\prime }}\le 500$ GeV. However, for much of this range the LHC bound is weaker than the bound that can be derived from searches for trident events in neutrino-nucleus scattering.

15 pages, 4 figures