Interpreting the 750 GeV diphoton excess by the singlet extension of the Manohar-Wise Model

TL;DR

This paper extends the Manohar-Wise model by adding a singlet scalar to explain the 750 GeV diphoton excess, fitting the data with new colored scalars mediating interactions, and analyzing experimental constraints.

Contribution

It introduces a singlet scalar extension to the Manohar-Wise model that can account for the diphoton excess through loop-mediated interactions involving new colored scalars.

Findings

The model can explain the diphoton excess at 1σ level.

Best fit points match the excess rate with high p-value.

Constraints from LHC Run I do not exclude the best-fit parameter regions.

Abstract

The evidence of a new scalar particle $X$ from the 750 GeV diphoton excess, and the absence of any other signal of new physics at the LHC so far suggest the existence of new colored scalars, which may be moderately light and thus can induce sizable $X g g$ and $X \gamma \gamma$ couplings without resorting to very strong interactions. Motivated by this speculation, we extend the Manohar-Wise model by adding one gauge singlet scalar field. The resulting theory then predicts one singlet dominated scalar $\phi$ as well as three kinds of color-octet scalars, which can mediate through loops the $\phi gg$ and $\phi \gamma \gamma$ interactions. After fitting the model to the diphoton data at the LHC, we find that in reasonable parameter regions the excess can be explained at $1\sigma$ level by the process $ g g \to \phi \to \gamma \gamma$, and the best points predict the central value of the excess rate with $\chi_{min}^2=2.32$, which corresponds to a $p$-value of $0.68$. We also consider the constraints from various LHC Run I signals, and we conclude that, although these constraints are powerful in excluding the parameter space of the model, the best points are still experimentally allowed.