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 $\texttt{ SHiP}$.
Categories: hep-ph