Improved KL->pi e nu Form Factor and Phase Space Integral with Reduced Model Uncertainty

TL;DR

This paper presents a refined measurement of the KL->pi e nu decay form factor and phase space integral, significantly reducing the uncertainty through a new form factor expansion with rigorous bounds, based on extensive decay data.

Contribution

The study introduces a novel form factor expansion with strict bounds, leading to a more precise determination of the phase space integral with minimal model uncertainty.

Findings

Phase space integral IKe = 0.15392 ± 0.00048

Uncertainty in form factor expansion is negligible

Overall uncertainty in IKe is halved compared to previous results

Abstract

Using the published KTeV sample of 2 million KL-> pi e nu decays and a new form factor expansion with a rigorous bound on higher order terms, we present a new determination of the KL->pi e nu form factor and phase space integral. Compared to the previous KTeV result, the uncertainty in the new form factor expansion is negligible and results in an overall uncertainty in the phase space integral (IKe) that is a factor of two smaller: IKe = 0.15392 +- 0.00048 \.