Measurement of the $K^{+}\to {\pi }^{+}\gamma \gamma$ decay

Abstract

A sample of 3984 candidates of the $K^{+}\to {\pi }^{+}\gamma \gamma$ decay, with an estimated background of $291\pm 14$ 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 $(9.61\pm 0.17)\times 10^{-7}$. The first search for production and prompt decay of an axion-like particle with gluon coupling in the process $K^{+}\to {\pi }^{+}a$, $a\to \gamma \gamma$ is also reported.

Revised version, accepted for publication in Physics Letters B

References in corpus (1)

• The integrated low-level trigger and readout system of the CERN NA62 experiment

Cited by in corpus (5)

• Wess-Zumino-Witten Interactions of Axions
• Search for hadronic decays of feebly-interacting particles at NA62
• Constraining axion-gluon coupling in monohadron processes
• Sweeping the pion chimney for axion-like particles with KOTO
• $K\to \pi {\gamma }^{\ast }{\gamma }^{\ast }$ transitions at leading order and beyond