PubDB | BELLE2-PUB-DRAFT-2024-022

Abstract	Inelastic dark matter models that feature two dark matter particles and a massive dark photon can reproduce the observed relic dark matter density without violating cosmological limits. The mass splitting between two dark matter particles chi1 and chi2 with mchi2 > mchi1 is induced by a dark Higgs field and a corresponding dark Higgs boson h'. We present a search for dark matter in events with two vertices, at least one of which must be displaced, and missing energy. Based on a sample corresponding to an integrated luminosity of 364fb-1 collected at Belle II, we observe no evidence for signal. We set upper limits on the product of branching fractions, where $x^+x^-$ indicates $\mu^+\mu^-, \pi^+\pi^-$, or $K^+K^-$, as functions of h' mass and lifetime at the level of 1e-1 fb. We set model-dependent upper limits on the dark Higgs mixing angle at the level of 1e-5 and on the dark photon kinetic mixing parameter at the level of 1e-3. This is the first search for dark Higgs bosons in association with inelastic dark matter.
Tags	Run 1
Working group	Dark Sector and Low Multiplicity
Principal authors	@ Giacomo De Pietro, Patrick Ecker, Jonas Eppelt, Torben Ferber, Pablo Goldenzweig
Reference	published in PRL
Document	BELLE2-PUB-DRAFT-2024-022
Links	arXiv:2505.09705,

Abstract

Inelastic dark matter models that feature two dark matter particles and a massive dark photon can reproduce the observed relic dark matter density without violating cosmological limits. The mass splitting between two dark matter particles chi1 and chi2 with mchi2 > mchi1 is induced by a dark Higgs field and a corresponding dark Higgs boson h'. We present a search for dark matter in events with two vertices, at least one of which must be displaced, and missing energy. Based on a sample corresponding to an integrated luminosity of 364fb-1 collected at Belle II, we observe no evidence for signal. We set upper limits on the product of branching fractions, where $x^+x^-$ indicates $\mu^+\mu^-, \pi^+\pi^-$, or $K^+K^-$, as functions of h' mass and lifetime at the level of 1e-1 fb. We set model-dependent upper limits on the dark Higgs mixing angle at the level of 1e-5 and on the dark photon kinetic mixing parameter at the level of 1e-3. This is the first search for dark Higgs bosons in association with inelastic dark matter.

Search for a Dark Higgs produced in association with inelastic Dark Matter at the Belle II experiment