Measurement of the K+ → π+γγ decay

UNSPECIFIED (2024) Measurement of the K+ → π+γγ decay. Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics, 850: 138513. p. 138513.

Text (2311.01837) - Accepted Version
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Text (2311.01837)
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Abstract

A sample of 3984 candidates of the K +→π +γγ decay, with an estimated background of 291±14 events, was collected by the NA62 experiment at CERN during 2017–2018. In order to describe the observed di-photon mass spectrum, the next-to-leading order contribution in chiral perturbation theory was found to be necessary. The decay branching ratio in the full kinematic range is measured to be (9.61±0.17)×10 −7. The first search for production and prompt decay of an axion-like particle with gluon coupling in the process K +→π +a, a→γγ is also reported.