Gluon-gluon fusion contribution to the productions of three gauge bosons at the LHC

TL;DR

This paper calculates the gluon-gluon fusion contribution to three gauge boson production at the LHC, finding it negligible for some processes but potentially significant for others at future colliders.

Contribution

It provides the first detailed estimates of gluon-gluon fusion effects on three gauge boson production, highlighting their varying significance across different processes.

Findings

Gluon-gluon contribution is about 0.1% for Zγγ production.

Gluon-gluon contribution is about 0.01% for ZZγ production.

Gluon-gluon contribution is approximately 5% for W+W−γ production.

Abstract

Productions of multiple gauge bosons at the LHC are sensitive to triple or quartic gauge couplings and thus provide a sensitive test for the electroweak sector of the Standard Model and allow for a probe of new physics. In this work we calculate the gluon-gluon initiate state contribution to the productions of three gauge bosons ($Z\gamma\gamma$, $ZZ\gamma$ and $W^+W^-\gamma$) at the LHC, which is formally part of NNLO effects compared to the LO quark-antiquark channels corrections. For each process we present the ratio between the gluon-gluon channels contribution and the quark-antiquark channels contribution. We found that such a ratio for $Z\gamma\gamma$ ($ZZ\gamma$) is of the order of $10^{-3}$ ($10^{-4}$), much smaller than the corresponding ratio for the diboson production due to the decrease of gluon PDF when more particles appear in the final states. These small ratios imply that gluon-gluon fusion contribution is phenomenological negligible for the productions of $Z\gamma\gamma$ and $ZZ\gamma$. However, for $W^+W^-\gamma$ production, the ratio is about 5\%, which is of the same order of magnitude as the ratio for $W^+W^-$ production due to the big cancellation between the amplitudes of quark-antiquark channels. While such an effect can be neglected currently at the LHC, it may be accessible at the HL-LHC.