2025/05/14 by I. Adachi, Belle II Collaboration, L. Aggarwal +534 · 1 citation
Computer Science · Physics and Astronomy · #Computational Physics and Python Applications #Dark Matter and Cosmic Phenomena #FOS: Physical sciences #High Energy Physics - Experiment (hep-ex) #Particle physics theoretical and experimental studies
paper · doi:10.48550/arxiv.2505.09705
openalex publication_date 2025/05/14 · openalex created_date 2025/10/15 · openalex updated_date 2026/07/28
Inelastic dark matter models that have 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 the two dark matter particles χ1 and χ2, with m(χ2) > m(χ1), 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 from the interaction region, and missing energy. Using a 365 fb-1 data sample collected at Belle II, which operates at the SuperKEKB e+e- collider, we observe no evidence for a signal. We set upper limits on the product of the production cross section σ(e+e- → h^′ χ1 χ2), and the product of branching fractions B(χ2→χ1 e+ e-)\timesB(h^′→ x+x-), where x+x- indicates μ+μ-, π+π-, or K+K-, as functions of h′ mass and lifetime at the level of 10-1 fb. We set model-dependent upper limits on the dark Higgs mixing angle at the level of 10-5 and on the dark photon kinetic mixing parameter at the level of 10-3. This is the first search for dark Higgs bosons in association with inelastic dark matter.