Search for Axionlike Particles Produced in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mi>e</mml:mi><mml:mo>+</mml:mo></mml:msup><mml:msup><mml:mi>e</mml:mi><mml:mo>−</mml:mo></mml:msup></mml:math> 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 ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\ensuremath{\gamma}a$, $a\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma}$ in the mass range $0.2&lt;{m}_{a}&lt;9.7\text{ }\text{ }\mathrm{GeV}/{c}^{2}$ using data corresponding to an integrated luminosity of $(445\ifmmode\pm\else\textpm\fi{}3)\text{ }\text{ }{\mathrm{pb}}^{\ensuremath{-}1}$. 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 ${g}_{a\ensuremath{\gamma}\ensuremath{\gamma}}$ of ALPs to photons at the level of ${10}^{\ensuremath{-}3}\text{ }\text{ }{\mathrm{GeV}}^{\ensuremath{-}1}$. The limits are the most restrictive to date for $0.2&lt;{m}_{a}&lt;1\text{ }\text{ }\mathrm{GeV}/{c}^{2}$.

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