K^+ -> pi^+pi^0e^+e^-: a novel short-distance probe

TL;DR

This paper analyzes the decay K^+ -> pi^+ pi^0 e^+ e^- to explore short-distance physics, focusing on Dalitz plot analysis and charge asymmetries to identify potential new physics signals.

Contribution

It provides a detailed analysis of the decay's Dalitz plot and charge asymmetries, proposing methods to detect short-distance effects in K^+ decays, and compares this process to related decays.

Findings

Charge asymmetries are effective for detecting short-distance effects.

The decay offers advantages over related processes for probing new physics.

Detailed predictions for asymmetry signals in K^+ -> pi^+ pi^0 e^+ e^-.

Abstract

We study the decay K^+ -> pi^+ pi^0 e^+ e^-, currently under analysis by the NA62 Collaboration at CERN. In particular, we provide a detailed analysis of the Dalitz plot for the long-distance, gamma^*-mediated, contributions (Bremsstrahlung, direct emission and its interference). We also examine a set of asymmetries to isolate genuine short-distance effects. While we show that charge asymmetries are not required to test short distances, they provide the best environment for its detection. This constitutes by itself a strong motivation for NA62 to study K^- decays in the future. We therefore provide a detailed study of different charge asymmetries and the corresponding estimated signals. Whenever possible, we make contact with the related processes K^+ -> pi^+ pi^0 gamma and K_L -> pi^+ pi^- e^+ e^- and discuss the advantages of K^+ -> pi^+ pi^0 e^+ e^- over them.