Discovery potential of a long-lived partner of inelastic dark matter at MATHUSLA in $U(1)_{X_3}$ extension of the standard model

TL;DR

This paper explores the potential for detecting a long-lived particle from inelastic scalar dark matter in a specific $U(1)$ extension of the standard model at MATHUSLA, highlighting the model's unique features and experimental prospects.

Contribution

It introduces a novel $U(1)_{X_3}$ extension with a third generation-philic right-handed $U(1)$ that predicts long-lived particles detectable at MATHUSLA.

Findings

LLP travel distance can be around 100 meters.

Production cross section at 14 TeV LHC is about 10 fb.

Potential for discovery of LLP at MATHUSLA.

Abstract

We investigate the discovery potential at the MATHUSLA experiment of a long-lived particle (LLP), which is the heavier state of inelastic scalar dark matter (DM) in third generation-philic $U(1)$ ($U(1)_{X_3}$) extension of the standard model. Since the heavier state and DM state form the complex scalar charged under the $U(1)_{X_3}$, it is natural that the heavier state $P$ is almost degenerate with the DM state and hence long-lived. We find that third generation-philic right-handed $U(1)$, $U(1)_{R_3}$, model is the most interesting, because third generation-philic models are less constrained by the current experimental results and right-handed $U(1)$ interactions leave visible final decay products without produing neutrinos. For a benchmark of the model parameters consistent with the current phenomenological constraints, we find that the travel distance of the LLP can be $\mathcal{O}(100)$ m and the LLP production cross section at the 14 TeV LHC can be $\mathcal{O}(10)$ fb. Thus, we conclude that the LLP can be discovered at the MATHUSLA with a sufficiently large number of LLP decay events inside the MATHUSLA detector.