Exclusion limits on a scalar decaying to photons and distinguishing its production mechanisms

TL;DR

This paper establishes model-independent limits on a new scalar decaying to diphotons at the LHC, and demonstrates how multivariate analysis can differentiate its production mechanisms, aiding in understanding the underlying physics.

Contribution

It provides a framework to set limits on scalar production modes and introduces a multivariate approach to distinguish production mechanisms at the LHC.

Findings

Recast of ATLAS diphoton search constrains scalar mass and couplings.

Multivariate analysis effectively differentiates production mechanisms.

Effective field theory approach enables model-independent limits.

Abstract

LHC run-II has a great potential to search for new resonances in the diphoton channel. Latest 13 TeV data already put stringent limits on the cross sections in the diphoton channel assuming the resonance is produced through the gluon-gluon fusion. Many beyond the Standard Model (SM) theories predict TeV-scale scalars, which copiously decay to diphotons. Apart from the gluon-gluon fusion production, these scalars can also be dominantly produced in other ways too at the LHC namely through the quark-quark fusion or the gauge boson fusions like the photon-photon, photon-$Z$, $WW$ or $ZZ$ fusions. In this paper, we use an effective field theory approach where a heavy scalar can be produced in various ways and recast the latest ATLAS diphoton resonance search to put model-independent limits on its mass and effective couplings to the SM particles. If a new scalar is discovered at the LHC, it would be very important to identify its production mechanism in order to probe the nature of the underlying theory. We show that combining various kinematic variables in a multivariate analysis can be very powerful to distinguish different production mechanisms one from the other.