Physical Review Letters 125, 161806 (2020)

ISSN: 0031-9007, SCIE

Search for Axionlike Particles Produced in e + e − Collisions at Belle II

The Belle II collaboration (F. Abudinén, ..., N. Anh Ky, ...)

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 < 9.7 GeV/c^2 using data corresponding to an integrated luminosity of (445 +_ 3) pb^−1. Light pseudoscalars interacting predominantly with standard model gauge bosons (so-called axionlike 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^−3 GeV^−1. The limits are the most restrictive to date for 0.2 < ma < 1 GeV/c^2.

DOI: 10.1103/PhysRevLett.125.161806

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