Formation of $\pi\mu$ atoms in $K_{\mu 4} decay

TL;DR

This paper derives the decay rate of $$ atoms formed in $K_{}4$ decay and assesses its significance as a background in rare kaon decay experiments.

Contribution

It provides the first calculation of the $$ atom formation rate in $K_{}4$ decay, highlighting its potential impact on experimental measurements.

Findings

Calculated decay rate of $$ atom formation in $K_{}4$ decay.

Identified $$ atom formation as a notable background in $K^+ o ^+ uar{ u}$ decay searches.

Abstract

We derive the decay rate of $\pi\mu$ atom formation in $K_{\mu 4}$ decay. Using the obtained expressions we calculate the decay rate of atom formation and point out that considered decay can give a noticeable contribution as a background to the fundamental decay $K^+\to \pi^+\nu\bar{\nu}$.