Deciphering the CP nature of the 750 GeV resonance

TL;DR

This paper investigates the nature of a 750 GeV resonance observed in diphoton events, exploring its CP properties, production channels, and potential for detection at the LHC, emphasizing the importance of asymmetries and decay modes.

Contribution

It introduces novel methods to determine the CP nature of a new scalar singlet and analyzes various production and decay channels for experimental testing.

Findings

Asymmetries can effectively distinguish CP properties of the resonance.

The $2\gamma 2j$ channel offers promising detection prospects at the LHC.

A significant portion of parameter space can be probed with current LHC data.

Abstract

The recently observed excess in diphoton events at around 750\,GeV can be satisfactorily described in terms of a new spin-0 real singlet with effective interactions to the gauge bosons. In this letter we first review the current constraints on this setup. We further explore the production in association with a gauge boson. We show the potential of this channel to unravel current flat directions in the allowed parameter space. We then study the potential of two different asymmetries for disentangling the CP nature of such a singlet in both gluon fusion and vector-boson fusion. For this matter, we perform an estimation of the efficiency for selecting signal and background events in eight different decay modes, namely $4\ell, 2j\, 2\ell, 2j\ell\,E_T^\text{miss}, 2\gamma\,2j, 4\ell\,2j, 2\ell\,\gamma\,2j, 4j\,2\ell$ and $4j\,\ell\,E_T^\text{miss}$. We emphasize that the very different couplings of this new singlet to the Standard Model particles as well as the larger mass provide a distinctive phenomenology with respect to Higgs searches. We finally show that a large region of the parameter space region could be tested within the current LHC run, the dominant channel being $2\gamma\, 2j$.