Long-Lived Fermions at AL3X

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 $\texttt{SHiP}$.