Heavy photophilic scalar at the LHC from a varying electromagnetic coupling

TL;DR

This paper explores a heavy scalar particle linked to varying electromagnetic coupling theories, analyzing its production and decay at the LHC, and setting limits on its parameters based on diphoton resonance data.

Contribution

It introduces a model of a heavy scalar with two free parameters, analyzing its LHC phenomenology and deriving experimental constraints from current data.

Findings

Lower limit on scale Λ of 18 TeV for 1 TeV scalar mass

Dominant decay to diphotons with significant three-body fermion-photon decay

Potential for new physics related to extra dimensions or string theory

Abstract

We investigate the phenomenology of a heavy scalar $\phi$ of the type involved in Bekenstein's framework for varying electromagnetic coupling theories, with the difference that the scalar in our model has a large mass. The model has only two free parameters, the mass $M_{\phi}$ of the scalar and the scale $\Lambda$ of new physics. The scalar is dominantly produced through photon-photon fusion at the LHC and leads to a diphoton final state. It can also be produced by quark-antiquark fusion in association with a photon or a fermion pair. Its dominating decay is to diphotons, but it also has a large three-body branching to a fermion pair and a photon, which can provide an interesting search channel with a dilepton-photon resonance. We derive exclusion limits on the $M_{\phi}-\Lambda$ plane from the latest 13 TeV LHC diphoton resonance search data. For a benchmark mass of $M_{\phi}\sim 1$ TeV, we find a lower limit on $\Lambda$ of 18 TeV. We discuss the more complex possibility of varying couplings in the full electroweak theory and comment on the possibility that the new physics is related to extra dimensions or string theory.