Study of K^0 \to pi^- e^+ nu_e e^+ e^- in chiral perturbation theory

TL;DR

This paper investigates the decay process K^0 to pi^- e^+ nu_e e^+ e^- using chiral perturbation theory up to next-to-leading order, revealing significant effects on lepton invariant mass and neutrino energy distributions.

Contribution

It provides the first detailed analysis of this decay mode at O^4 in chiral perturbation theory, highlighting the importance of higher-order corrections.

Findings

O^4 terms significantly alter invariant mass distributions.

Energy spectrum of neutrinos is notably affected.

Next-to-leading order calculations improve theoretical predictions.

Abstract

K^0 \to pi^- e^+ nu_e e^+ e^- decay is studied up to the next-to-leading order O^4 in chiral perturbation theory. It is found that the O^4 terms appreciably modifiy the shape of the invariant mass distribution of the leptons and the energy spectrum of the neutrino.