Search for Axion-Like Particles produced in e+e− collisions at Belle II
We present a search for the direct production of a light pseudoscalar a decaying into two photons with the Belle II detector at the SuperKEKB collider. We search for the process e+e−→γa,a→γγ in the mass range 0.2<ma<9.7GeV/c2 using data corresponding to an integrated luminosity of (445±3)pb−1. Light pseudoscalars interacting predominantly with standard model gauge bosons (so-called axion-like particles or ALPs) are frequently postulated in extensions of the standard model. We find no evidence for ALPs and set 95% confidence level upper limits on the coupling strength gaγγ of ALPs to photons at the level of 10−3GeV−1. The limits are the most restrictive to date for 0.2<ma<1GeV/c2.