Abstract
In the minimal supersymmetric standard model (MSSM) the bino-wino coannihilation provides a feasible way to accommodate the observed cosmological dark matter (DM) relic density. However, such a scenario usually predicts a very small DM-nucleon scattering cross section that is below the neutrino floor, and can not be tested by DM direct detection experiments. In this work, we investigate the discovery potential of this bino-wino co-annihilation region by searching for the soft dilepton events from the process $pp \to \chi^0_2 (\to \ell^+\ell^- \chi^0_1) \chi^\pm_1+jets$ at the LHC. We find that the mass of the wino-like $\chi^0_2$ can be probed up to about 310 (230) GeV at $2\sigma$ ($5\sigma$) level for an integrated luminosity ${\cal L}=300$ fb$^{-1}$. In the future HL-LHC with 3000 fb$^{-1}$ luminosity, the corresponding mass limits can be pushed up to 430 (330) GeV.
Highlights
Dark matter accounts for about 27% of the global energy budget in the Universe
The weakly interacting massive particles (WIMPs) dark matter (DM) may interact with the nucleons at loop levels [4] or annihilate with a light species
We can see that the SI cross sections for bino-wino coannihilation samples are very small because of the tiny couplings of bino-like LSP with the Higgs boson2 Most of them are even below the neutrino floor so that they can escape the existing strong limits from PandaX-II(2017), XENON1T(2017), XENON100(2016), LUX(2017) and the future direct detection experiments, such as LUX-ZEPLIN, which will improve the current sensitivity of LUX by about two orders of magnitude
Summary
Dark matter accounts for about 27% of the global energy budget in the Universe. it has not yet been directly detected and its identity remains a mystery. Given the strong LHC constraints on the colored SUSY particles and the nonobservation of DM in direct detections, the bino-wino coannihilation is one of the feasible ways that can provide the correct DM relic density and escape the direct detections [15,17,18]. It may happen in the so-called split supersymmetry [19,20,21,22], the spread supersymmetry [23] or supersymmetric GUT models with nonuniversal gaugino masses at the boundary [15].
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