Precision measurements of kaon and pion decays at NA62

Jun 12, 2025, 11:30 AM
20m
Plenary presentation Precision Physics at High Intensities Plenary

Speaker

Peter Cooper (George Mason Univ)

Description

The NA62 experiment at CERN collected the world's largest dataset of charged kaon decays, leading to the most precise measurement of the branching ratio of the ultra-rare $K^+ \rightarrow \pi^+ \nu \bar\nu$ decay. In this talk NA62 reports recent results from precision measurements of kaon and pion decays, using data samples collected in 2017-2018. A sample of $K^+ \rightarrow \pi^+ \gamma \gamma$ decays is collected using a minimum-bias trigger, and the results include measurement of the branching ratio, study of the di-photon mass spectrum, and the first search for production and prompt decay of an axion-like particle with gluon coupling in the process $K^+ \rightarrow \pi^+ A$, $A \rightarrow \gamma \gamma$. A sample of $\pi^0 \rightarrow e^+ e^-$ decay candidates is collected using a dedicated scaled down di-electron trigger, and a preliminary result of the branching fraction measurement is presented. The radiative kaon decay $K^+ \rightarrow \pi^0 e^+ \nu \gamma$ (Ke3g) is studied with a data sample of O(100k) Ke3g candidates with sub-percent background contaminations. Results with the most precise measurements of the Ke3g branching ratios and T-asymmetry are presented. The $K^+ \rightarrow \pi^+ \mu^+ \mu^-$ sample comprises about 27k signal events with negligible background contamination, and the presented analysis results include the most precise determination of the branching ratio and the form factor.

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