# Last Electroweak WIMP Standing: Pseudo-Dirac Higgsino Status and Compact Stars as Future Probes

## TL;DR

This paper reviews current constraints on pseudo-Dirac higgsino dark matter, explores astrophysical probes like white dwarf heating, and discusses future observational prospects to detect or constrain such elusive WIMPs.

## Contribution

It provides an updated assessment of experimental bounds on higgsino dark matter and proposes novel astrophysical methods for future detection.

## Key findings

- AMS-02 antiproton measurements impose strong bounds with uncertainties.
- White dwarf heating could serve as a new indirect detection method.
- Astrophysical observations may help probe the challenging MeV mass splitting regime.

## Abstract

Electroweak WIMPs are under intense scrutiny from direct detection, indirect detection, and collider experiments. Nonetheless the pure (pseudo-Dirac) higgsino, one of the simplest such WIMPs, remains elusive. We present an up-to-date assessment of current experimental constraints on neutralino dark matter. The strongest bound on pure higgsino dark matter currently may arise from AMS-02 measurements of antiprotons, though the interpretation of these results has sizable uncertainty. We discuss whether future astrophysical observations could offer novel ways to test higgsino dark matter, especially in the challenging regime with order MeV mass splitting between the two neutral higgsinos. We find that heating of white dwarfs by annihilation of higgsinos captured via inelastic scattering could be one useful probe, although it will require challenging observations of distant dwarf galaxies or a convincing case to be made for substantial dark matter content in Omega Centauri, a globular cluster that may be a remnant of a disrupted dwarf galaxy. White dwarfs and neutron stars give a target for astronomical observations that could eventually help to close the last, most difficult corner of parameter space for dark matter with weak interactions.