ALP-Mediated Dark Matter at Low Reheating Temperature and the Belle II Excess

Joel Jones-Pérez, Luca Merlo, Javier Silva-Malpartida

Belle II has reported a $2.7\sigma$ excess in $B^{+}\to K^{+}\nu \bar{\nu }$ over its Standard Model prediction, recently interpreted as arising from an axion-like particle mediating a thermal dark…