Search for Light Neutral Scalar in the Georgi-Machacek Model with Forward Detectors at the LHC

TL;DR

This paper explores the potential of forward detectors at the LHC to detect long-lived neutral scalars predicted by the Georgi-Machacek model, highlighting their sensitivity to parameter regions beyond traditional methods.

Contribution

It demonstrates that forward detectors can effectively probe long-lived neutral scalars in the Georgi-Machacek model, extending the search for extended Higgs sectors.

Findings

Forward detectors can probe $s_H$ down to ~10^{-5} for sub-GeV scalars.

Long-lived $H_5^0$ can be produced via meson decay with observable signatures.

The method complements existing terrestrial and astrophysical constraints.

Abstract

Long-lived particle (LLP) is one of the well-motivated targets for current collider experiments searching for the physics beyond the Standard Model. In recent years, many dedicated detectors have been developed for such scenarios which are designed to extend the sensitivity to weakly coupled particles with macroscopic $c\tau$. In this work, we investigate the LLP signatures of the neutral component of the fermiophobic fiveplet $H_5^0$ in the Georgi-Machacek model. Due to its fermiophobic nature at tree level, it possesses suppressed decay widths in the low mass region and can naturally be long-lived over a wide region of parameter space. We show that $H_5^0$ can be produced with an appreciable flux in the forward region from the meson decay through loop-induced couplings leading to observable LLP signatures in forward detectors. We evaluate the sensitivity of representative forward detectors to this scenario and compare the result with existing constraints from terrestrial experiments and astrophysical observations. Our results demonstrate that the forward detectors can probe the $s_H$ down to $\mathcal{O}(10^{-5})$ for sub-GeV scalar masses, and hence providing a powerful and complementary probe of the extended Higgs sectors that is inaccessible to conventional searches.