Probing bino-wino coannihilation dark matter below the neutrino floor at the LHC

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 $pp\to {\chi }_2^0(\to {\ell }^{+}{\ell }^{-}{\chi }_1^0){\chi }_1^{\pm }+\text{jets}$ at the LHC. We find that the mass of the winolike ${\chi }_2^0$ can be probed up to about 310 (230) GeV at $2\sigma$ ($5\sigma$) level for an integrated luminosity $\mathcal{L}=300{\mathrm{fb}}^{-1}$. In the future HL-LHC with $3000{\mathrm{fb}}^{-1}$ luminosity, the corresponding mass limits can be pushed up to 430 (330) GeV.

Figure 1

The scatter plots of bino-wino coannihilation on the plane of $m_{{\chi }_1^0}$ versus $m_{{\chi }_2^0}$. All samples satisfy the constraints (i) and (ii).

Figure 2

Same as Fig. 1, but for the spin-independent and spin-dependent neutralino LSP-nucleon scattering cross sections. The observed 90% C.L. upper limits are from PandaX-II with a total exposure of $90.4\mathrm{kg}\times \mathrm{yr}$ [3], XENON1T (2017) with a total exposure of $97.1\mathrm{kg}\times \mathrm{yr}$ [2], XENON100 (2016) with a total exposure of $48\mathrm{kg}\times \mathrm{yr}$ [48] and LUX (2017) with a total exposure of $129.5\mathrm{kg}\times \mathrm{yr}$ [49]. The projected LUX-ZEPLIN with a exposure of $153.4\times {10}^2\mathrm{kg}\times \mathrm{yr}$ [50] sensitivity limits are plotted.

Figure 3

The cross section of $pp\to {\chi }_2^0{\chi }_1^{\pm }$ at the 13 TeV LHC. Here $M_1=M_2-30\mathrm{GeV}$ and $\tan \beta =30$.

Figure 4

Diagram representing for the process $pp\to {\chi }_2^0{\chi }_1^{\pm }+\mathrm{jets}$, ${\chi }_2^0\to Z^{*}{\chi }_1^0\to {\ell }^{+}{\ell }^{-}{\chi }_1^0$.

Figure 5

Same as Fig. 1, but show the statistical significance ($\alpha$) of the process $pp\to {\chi }_2^0{\chi }_1^{\pm }+\mathrm{jets}$ on the plane of $m_{{\chi }_2^0}$ versus $m_{{\chi }_2^0}-m_{{\chi }_1^0}$ at the 13 TeV LHC with the luminosity $\mathcal{L}=300$, $3000{\mathrm{fb}}^{-1}$. The gray, blue and red bullets denote $\alpha <2\sigma$, $2\sigma <\alpha <5\sigma$ and $\alpha >5\sigma$, respectively.