Abstract
Recently Gligorov $\textit{et al.}$ [arXiv:1810.03636] proposed to build a cylindrical detector named '$\texttt{AL3X}$' close to the $\texttt{ALICE}$ experiment at interaction point (IP) 2 of the LHC, aiming for discovery of long-lived particles (LLPs) during Run 5 of the HL-LHC. We investigate the potential sensitivity reach of this detector in the parameter space of different new-physics models with long-lived fermions namely heavy neutral leptons (HNLs) and light supersymmetric neutralinos, which have both not previously been studied in this context. Our results show that the $\texttt{AL3X}$ reach can be complementary or superior to that of other proposed detectors such as $\texttt{CODEX-b}$, $\texttt{FASER}$, $\texttt{MATHUSLA}$ and $\texttt{SHiP}$.
Highlights
There has recently been an increased interest in neutral long-lived particles (LLPs)
Our results show that the AL3X reach can be complementary or superior to that of other proposed detectors such as CODEX-b, FASER, MATHUSLA and SHiP
Before we present the sensitivity estimates, we compare the average decay probability hP1⁄2LLP in d:r:i, called fiducial efficiencies εfid in Ref. [10], of AL3X and MATHUSLA for the different benchmark models considered in this study
Summary
There has recently been an increased interest in neutral long-lived particles (LLPs). Very recently a further experiment has been proposed, AL3X [10], which would be located at the ALICE site at the LHC It differs from MATHUSLA, CODEX-b and FASER in that the center of the detector is located only 11.25 m from the ALICE IP, and the detector would have a magnet. In this paper we shall focus on two examples: (a) heavy neutral leptons (HNLs) These are often called sterile neutrinos in the literature. We have investigated the search sensitivity of MATHUSLA, CODEX-b and FASER for these specific HNFs [15,16] It is the purpose of this paper to directly extend this recent work and investigate the sensitivity of the proposed AL3X detector to these HNFs, i.e., sterile neutrinos, as well as the lightest neutralino in supersymmetry, as they were not considered in the original AL3X paper [10].
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