Constraining the heavy leptophilic neutral gauge bosons through the $Z\to\ell^+\ell^-$, $W^\pm\to\ell^\pm\nu_\ell$, and $h\to\ell^+\ell^-$ decays

TL;DR

This paper investigates how heavy leptophilic Z' bosons can be constrained through their loop effects on electroweak and Higgs decays, providing stronger limits on such new physics interactions.

Contribution

It introduces a method to set tighter bounds on heavy leptophilic Z' bosons using decay width measurements of Z, W, and Higgs bosons, complementing collider searches.

Findings

Current decay data impose strong limits on heavy Z' interactions.

Loop corrections to decay widths can reveal or constrain leptophilic Z' bosons.

Future collider data can further tighten these constraints.

Abstract

We consider the hypothetical possibility of neutral gauge bosons~($Z^\prime$) with flavor-specific leptophilic couplings. For such {\it New Physics}~(NP) interactions, the current experimental constraints are much relaxed in the heavy mass regime, particularly for masses $\geq \mathcal{O}(1)$ TeV. However, in the presence of a leptophilic $Z^\prime$, leptonic decay modes of the electroweak gauge bosons and Higgs can be corrected at the loop level. Using the existing upper bounds on the corresponding decay widths, we find that one can impose stronger exclusion limits on the interactions of a heavy $Z^\prime$. Future updates on the aforesaid decay channels can be used in complementarity with the proposed lepton colliders to probe even weaker leptophilic NP interactions at the TeV scale and beyond.