Probing stops in the coannihilation region at the HL-LHC: a comparative study of different processes

Abstract

In the minimal supersymmetric model, the coannihilation of the lighter stop ${\tilde{t}}_1$ and bino-like dark matter $\ddot{I}‡$ provides a feasible way to accommodate the correct dark matter relic abundance. In this scenario, due to the compressed masses, ${\tilde{t}}_1$ merely appears as missing energy at the LHC and thus the pair production of ${\tilde{t}}_1$ can only be probed by requiring an associated energetic jet. Meanwhile, since ${\tilde{t}}_2$ and ${\tilde{b}}_1$ are correlated in mass and mixing with ${\tilde{t}}_1$, the production of ${\tilde{t}}_2{\tilde{t}}_2^{\ast }$ or ${\tilde{b}}_1{\tilde{b}}_1^{\ast }$, each of which dominantly decays into ${\tilde{t}}_1$ plus $Z$, $h$ or $W$ boson, may serve as a complementary probe. We examine all these processes at the HL-LHC and find that the $2\ddot{I}ƒ$ sensitivity to $\ddot{I}‡$ mass can be as large as about 570 GeV, 600 GeV and 1.1 TeV from the production process of ${\tilde{t}}_1{\tilde{t}}_1^{\ast }+\mathrm{jet}$, ${\tilde{t}}_2{\tilde{t}}_2^{\ast }$ and ${\tilde{b}}_1{\tilde{b}}_1^{\ast }$, respectively.

16 pages,9 figures