New results on kaon decays from NA48/2

TL;DR

This paper reports new measurements from the NA48/2 experiment on kaon decay parameters, including scattering lengths, branching ratios, and form factors, advancing understanding of kaon decay processes and related fundamental interactions.

Contribution

It provides novel experimental results on kaon decay parameters, including scattering lengths and decay rates, using data from the NA48/2 experiment, which were not previously available.

Findings

Measured $ ext{a}_0^0$ and $ ext{a}_0^2$ scattering lengths from cusp analysis.

Determined branching ratios for several kaon decay modes.

Extracted form factors for specific kaon decay channels.

Abstract

Recent results from the NA48/2 experiment are presented. The $\pi\pi$ scattering lengths $a_0^0$ and $a_0^2$ have been extracted from the cusp in the $M_{00}^2$ distribution of $K^\pm \to \pi^\pm \pi^0 \pi^0$ decays and from the $K^\pm \to \pi^+ \pi^- e^\pm \nu$ phase shift $\delta$. Branching ratios and form factors have been measured for {$K^\pm \to \pi^\pm \gamma \gamma$}, {$K^\pm \to \pi^\pm \gamma e^+ e^-$} and {$K^\pm \to \pi^\pm e^+ e^-$} decays and are also summarized here.