Unitarity limits on triple gauge boson production

TL;DR

This work derives unitarity bounds on dimension-eight genuine QGC operators within a linearly realized SM EFT by analyzing three-particle partial waves in the process $FF\to VVV$ and compares them to the established $VV\to VV$ limits. It shows that, although triple-gauge production amplitudes can grow as $S_{VVV}^2$, the resulting unitarity bounds on $f_X/\Lambda^4$ are generically weaker than those from diboson scattering due to smaller coefficients and larger phase-space factors. The operators are categorized into ${\cal O}_{S,i}$, ${\cal O}_{M,i}$, and ${\cal O}_{T,i}$, with explicit bounds for each class illustrating the hierarchy: $S$-type bounds are strong but still subdominant to $VV$; $M$- and $T$-type bounds are systematically looser. The results support the continued use of the clipping method in LHC analyses and demonstrate that current and upcoming QGC studies in exclusive $VVV$ production remain consistent with unitarity constraints from both two- and three-body channels, validating EFT-based interpretations within the clipped phase space.

Abstract

We derive the unitarity constraints on anomalous quartic gauge couplings originating from the $f \bar{f}^\prime \to V V' V''$ channel with $V^{(')('')}=γ$, $Z$, $W^\pm$, and $H$. We also assess the importance of these bounds on the present and future experimental searches.