  In the minimal supersymmetric model, the coannihilation of the lighter stop
$\tilde{t}_1$ and bino-like dark matter $\chi$ 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 $\tilde{t}_2\tilde{t}_2^*$ or $\tilde{b}_1\tilde{b}_1^*$, 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 $2\sigma$ sensitivity to $\chi$ mass can be as large as about
570 GeV, 600 GeV and 1.1 TeV from the production process of
$\tilde{t}_1\tilde{t}_1^*+{\rm jet}$, $\tilde{t}_2\tilde{t}_2^*$ and
$\tilde{b}_1\tilde{b}_1^*$, respectively.

High Energy Physics - Phenomenology