Signal for a light singlet scalar at the LHC

TL;DR

This paper explores the potential to detect a light singlet scalar particle at the LHC and future colliders, focusing on specific production and decay channels to improve search sensitivity.

Contribution

It introduces a novel search strategy for a light singlet scalar in the 20-100 GeV range via $pp o tar{t}S$ with $S o bar{b}$, extending current exploration.

Findings

Signal significance achievable with a few ab$^{-1}$ luminosity.

Future colliders can significantly improve current limits on scalar-Higgs mixing.

The proposed channel is promising for discovering light scalars in unexplored mass ranges.

Abstract

In the general Higgs portal like models, the extra neutral scalar, $S$, can mix with the Standard Model (SM) Higgs boson, $H$. We perform an exploratory study focusing on the direct search for such a light singlet $S$ at the Large Hadron Collider (LHC). After careful study of the SM background, we find the process $pp\rightarrow t\bar{t}S$ followed by $S\rightarrow b\bar{b}$ can be used to investigate $S$ with mass in the $20<M_S<100$ GeV range, which has not been well explored at the LHC. The signal significance becomes meaningful with a luminosity around a few $\mbox{ab}^{-1}$. Also, we study the prospects of finding the light scalar at the future 100 TeV $pp$ collider, the $Z$ and Higgs factories. With similar luminosity, the current LEP limits on the mixing between $S$ and $H$ can be improved by at least one or two orders of magnitude.