LHC and HL-LHC Bounds on Visible and Invisible Decays in the $B-L$ Model

Abstract

In this work, we use publicly available data from ATLAS collaboration collected at LHC run 2 at a center-of-mass energy of $\sqrt{s}=13$TeV with an integrated luminosity of $139f{b}^{-1}$ to derive lower mass limits on the $Z^{\prime }$ gauge boson associated with the B-L gauge symmetry. Using dilepton data we find that $M_{Z^{\prime }}>4$TeV ($6$TeV) for $g_{BL}=0.1$ ($g_{BL}=0.5$) in the absence of invisible decays. Once invisible decays are turned on these limits are substantially relaxed. Assuming an invisible branching ratio of $B{R}_{inv}=0.9$, the LHC bound is loosened up to $M_{Z^{\prime }}>4.8$TeV for $g_{BL}=0.5$. This analysis confirms that the LHC now imposes stricter constraints than the longstanding bounds established by LEP. We also estimate the projected HL-LHC bounds that will operate with at $\sqrt{s}=14$TeV and a planned integrated luminosity of $\mathcal{L}=3a{b}^{-1}$ that will probe $Z^{\prime }$ masses up to $7.5$TeV.

Comments: 7 pages, 7 figures