Probing Quartic Neutral Gauge Boson Couplings using diffractive photon fusion at the LHC

TL;DR

This paper investigates quartic neutral gauge boson couplings involving photons and Z-bosons, exploring their theoretical origins and proposing methods to detect them at the 14 TeV LHC through diffractive photon fusion processes, achieving unprecedented sensitivity.

Contribution

It provides a comprehensive list of operators contributing to these couplings, analyzes their generation in extra-dimensional models, and proposes experimental probes at the LHC with significantly improved sensitivity.

Findings

Photon fusion processes can probe couplings as small as 1/(1.8 TeV)^4.

Enhanced sensitivity over existing limits for g Z couplings.

Dimension 8 operators dominate in the light Higgs case, dimension 6 in the higgsless case.

Abstract

A complete list of operators contributing at the lowest order to Quartic Neutral Gauge Boson Couplings involving photons and Z-bosons, is presented. We show that, for the couplings we consider, the lowest order contribution is from dimension 8 operators in the case when a light Higgs is present and from dimension 6 operators in the higgsless case where electroweak symmetry is non-linearly realized. We also show that these operators are generated by exchange of the Kaluza-Klein partners of the graviton in extra-dimensional models. We then explore the possibility of probing these couplings in the diffractive photon fusion processes pp(\gamma\gamma \to \gamma\gamma)pp and pp(\gamma\gamma \to ZZ)pp at the 14 TeV LHC. We find that the \gamma \gamma \gamma \gamma-coupling can be probed most sensitively and values as small as 1/(1.8 TeV)^{4} can be measured. For the \gamma\gamma ZZ-coupling, values as small as 1/(850 GeV)^{4} and 1/(1.9 TeV)^2 can be probed in the light Higgs and higgsless cases respectively, which is an improvement by orders of magnitude over existing limits.