Chasing higgsino dark matter at colliders in the neutrino fog era

TL;DR

This paper examines the challenges of detecting higgsino dark matter at colliders amid increasing direct detection constraints, proposing collider signatures involving heavier superpartner decays as promising probes in the neutrino fog era.

Contribution

It analyzes current and future direct detection limits on higgsino purity and proposes collider search strategies involving decays of heavier superpartners to detect higgsino dark matter.

Findings

Current LUX-ZEPLIN limits set lower bounds on gaugino masses.

Projected direct detection sensitivities will approach the neutrino fog.

Decays of stop and wino pairs to higgsinos offer promising collider signatures.

Abstract

Higgsinos can be the lightest supersymmetric particles, allowing for either a full or partial dark matter interpretation, with the correct thermal freeze-out abundance obtained for masses near 1.1 TeV. Dark matter direct detection experimental results, now rapidly approaching the neutrino fog, imposes increasingly stringent requirements on higgsino purity. We begin by summarizing the purity constraints implied by the current strong limits from the LUX-ZEPLIN experiment in 2024, presenting them as lower bounds on gaugino masses in scenarios with decoupled sfermions and heavy Higgs bosons. We further quantify how these constraints will evolve as direct detection approaches various neutrino fog discovery and exclusion definitions and future exclusion projections. Finally, given that nearly pure higgsinos remain notoriously challenging to probe directly at colliders, we explore complementary signatures in which higgsinos are produced from the decays of heavier superpartners, where additional leptons and jets can be used for triggering. In particular, we advocate for searches of stop and wino pairs decaying directly to higgsinos as a promising means to probe higgsino dark matter well into the neutrino fog era.