Probing Neutral Triple Gauge Couplings at the LHC and Future Hadron Colliders

TL;DR

This paper investigates the potential of the LHC and future 100TeV colliders to probe neutral triple gauge couplings (nTGCs), deriving new relations for form factors and comparing sensitivities with electron-positron colliders.

Contribution

It introduces a generalized form factor formulation for nTGCs from dimension-8 SMEFT operators and analyzes collider sensitivities for the first time.

Findings

LHC sensitivities are comparable to sub-1TeV e+e- colliders.

Future 100TeV colliders can significantly improve nTGC constraints.

New relations ensure physically consistent form factor descriptions.

Abstract

We study probes of neutral triple gauge couplings (nTGCs) at the LHC and the proposed 100TeV $pp$ colliders, and compare their sensitivity reaches with those of the proposed $e^+ e^-$ colliders. The nTGCs provide a unique window to the new physics beyond the Standard Model (SM) because they can arise from SM effective field theory (SMEFT) operators that respect the full electroweak gauge group $SU(2)_L\otimes U(1)_Y$ of the SM only at the level of dimension-8 or higher. We derive the neutral triple gauge vertices (nTGVs) generated by these dimension-8 operators in the broken phase and map them onto a newly generalized form factor formulation, which takes into account only the residual U(1)$_{\rm{em}}$ gauge symmetry. Using this mapping, we derive new relations between the form factors that guarantee a truly consistent form factor formulation of the nTGVs and remove large unphysical energy-dependent terms. We then analyze the sensitivity reaches of the LHC and future 100TeV hadron colliders for probing the nTGCs via both the dimension-8 nTGC operators and the corresponding nTGC form factors in the reactions $ pp(q\bar{q})\to Z\gamma$ with $Z\to\ell^+\ell^-,\nu\bar{\nu}$. We compare their sensitivities with the existing LHC measurements of nTGCs and with those of the high-energy $e^+e^-$ colliders. In general, we find that the prospective LHC sensitivities are comparable to those of an $e^+ e^-$ collider with center-of-mass energy $\leq 1$TeV, whereas an $e^+ e^-$ collider with center-of-mass energy $(3 - 5)$TeV would have greater sensitivities, and a 100TeV $pp$ collider could provide the most sensitive probes of the nTGCs.