Alignment without Decoupling: the Portal to Light Dark Matter in the MSSM

TL;DR

This paper explores novel light dark matter candidates within the MSSM framework, focusing on the alignment without decoupling limit, and discusses their detectability through upcoming experiments and collider searches.

Contribution

It identifies three new scenarios for light neutralino dark matter in the MSSM with alignment without decoupling, linking Higgs phenomenology to dark matter properties.

Findings

Three distinct light dark matter scenarios identified.

All scenarios will be tested by next-generation direct detection experiments.

Unique Higgs signatures suggest dedicated LHC searches are needed.

Abstract

We study light, thermal neutralino dark matter in the sub-GeV to 65 GeV mass range in the Minimal Supersymmetric extension of the Standard Model (MSSM). We consider realizations of the limit of alignment without decoupling in the Higgs sector where the heavier CP-even Higgs impersonates the observed Higgs state at 125 GeV, while the lighter CP-even Higgs is the mediator of dark matter annihilation. We single out three distinct and novel possibilities for light dark matter: (i) a neutralino with mass around half the light Higgs mass, in the sub-GeV to 30 GeV mass range; (ii) a neutralino with a mass around half the pseudoscalar Higgs boson mass, in our examples around 60 to 65 GeV; (iii) a very light neutralino with mass around the light Higgs mass, pair-annihilating to Higgs pairs. We discuss the implications of all these possibilities for indirect and direct dark matter detection experiments, and we demonstrate that all scenarios will be tested by next generation direct detection experiments. We also emphasize that the unique Higgs phenomenology of these scenarios warrants a dedicated search program at the LHC.