TeV Higgsino Dark Matter from LZ Nuclear Recoil to Fermi-LAT Gamma Rays

Abstract

The excess of high-energy nuclear recoils, which was recently reported by the LUX-ZEPLIN (LZ) experiment, together with the Fermi-LAT Galactic-Center preference, suggests new physics beyond the standard model (SM). One of the minimal extensions of the SM is to introduce a fermionic electroweak doublet in which the lightest neutral component can play the role of a stable dark matter particle. We show that the minimal higgsino dark matter can offer a common origin for both excesses. The inferred mass splitting, however, depends on the local dark matter velocity distribution, and including the high-velocity tail generated by the gravitational influence of the Large Magellanic Cloud yields ${\delta }_m=481$--$519\mathrm{keV}$ for $m_{\chi }=1000$--$1183\mathrm{GeV}$ at $1\sigma$ level. Near elastic-scattering blind spots, solar-captured higgsinos fail to reach thermal equilibrium, weakening their annihilation signal, so that ten years of IceCube data exclude ${\delta }_m\lesssim 475\mathrm{keV}$ at 90% C.L. The viable parameter space can be tested through the associated gamma-ray line, which is within the projected reach of CTAO.

Updated version, two columns, 7+8 pages. Added numerical calculations of non-equilibrium annihilation of solar-captured dark matter and the LMC-enhanced high-velocity tail