Variations on a Higgs theme

TL;DR

This paper explores how Z bosons produced via gluon fusion can mimic Higgs signals in the di-photon channel, analyzing the impact of additional fermion states on these processes at different collider energies.

Contribution

It demonstrates the potential for Z boson production through gluon fusion to contribute to Higgs candidate signals and examines how new fermion states could influence these predictions.

Findings

At 7-8 TeV, the process is negligible at current LHC luminosities.

At 14 TeV, the process becomes accessible with higher luminosity (~300 fb$^{-1}$).

Additional fermion states can mimic Higgs signals in the di-photon channel.

Abstract

We show how the $Z$ boson can be generated in gluon-gluon fusion and yield two photons, via $gg\to Z\to \gamma\gamma$, through massive fermion loops only, thereby contributing events to a candidate Higgs sample in the di-photon channel. A sub-leading contribution also exists from $q\bar q\to Z\to\gamma\gamma$ events. Assuming the Standard Model, the corresponding event rates are negligible at the LHC stages of 7, 8 TeV, given the luminosities collected therein (about 5 and 20 fb$^{-1}$, respectively). Conversely, at 14 TeV, the first process become accessible for luminosities of order 300 fb$^{-1}$. Finally, we show how additional fermion states entering such loops, in production, in decay or in both cases, could affect the predictions in this channel by curiously mimicking Higgs signals.