Can the FCC-hh prove the B-L gauge symmetry?

Abstract

We present a phenomenological study of the discovery potential at the FCC-hh for a new heavy neutral vector boson, Z', predicted by the $U(1)_{B-L}$ gauge symmetry. Focusing on the parameter space currently not excluded by Large Hadron Collider data, we analyze the dilepton production channel $p p \rightarrow Z^{\prime} \rightarrow l^{+} l^{-}$ ($l^{\pm} = e^{\pm}, \mu^{\pm}$) at a center-of-mass energy of $\sqrt{s} = 100$ TeV. Full Monte Carlo simulations was performed for different ($M_{Z'}$, $g_{B-L}$) BSM scenarios and relevant Standard Model backgrounds (including irreducible Drell-Yan, diboson, single top-quark and top-quark pair productions) identifying optimal kinematic and angular selection cuts to guide future searches for this type resonance. We estimate the FCC-hh reach for an integrated luminosity of $\mathcal{L}_{int}$ = 3~$ab^{-1}$. Our results demonstrate that the FCC-hh can exclude Z' masses up to $\sim 40$ TeV with 95\% C.L. for couplings of $g_{B-L} \sim 1$, and up to $\sim 15$ TeV for $g_{B-L} \sim 0.1$. We find the kinematic and angular cuts that optimize the signal over background ratio and achieve a $5\sigma$ signal up to Z' masses of $\sim 30$ TeV. These findings highlight the FCC-hh potential to uncover new physics signals in the high-mass regime.