2025/12/22 by Wang, Zihan
#Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #High Energy Physics - Phenomenology (hep-ph)
paper · doi:10.48550/arxiv.2512.18959
We propose a scalar-mediated Self-Interacting Dark Matter (SIDM) model to address small-scale structure anomalies such as the core-cusp and diversity problems. The model is composed by a leptophilic scalar mediator and a pseudo-Dirac dark matter candidate with a mass splitting of 100 eV.We imposed aA dark discrete ℤ2 symmetry forbids tree-level elastic scattering. Therefore creates kinematic threshold that suppresses scattering in ultra-faint satellite galaxies while enabling large self-interaction cross-sections in dwarf galaxies via resonant enhancement. To satisfy Big Bang Nucleosynthesis (BBN) requirements, we introduce a dimension-5 magnetic dipole operator that enable the decay of the excited state (χ2 → χ1 γ). This operator also provides a unique, low-threshold signal for direct detection experiments, characterized by a distinct 1/ER recoil spectrum. We identify a benchmark parameter space around (mχ≈ 40 GeV, mϕ≈ 20 MeV) where non-perturbative coupled-channel dynamics successfully reconcile astrophysical observations with cosmological bounds, including CMB constraints on annihilation.