Search for axionlike particles produced in collisions at Belle II

Abudinn, F.*; Tanida, Kiyoshi   ; Belle II Collaboration*; 334 of others*

We present a search for the direct production of a light pseudoscalar decaying into two photons with the Belle II detector at the SuperKEKB collider. We search for the process in the mass range using data corresponding to an integrated luminosity of pb. 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 of ALPs to photons at the level of GeV. The limits are the most restrictive to date for GeV/.