Measurement of the $\pi^0$ electromagnetic transition form factor slope

TL;DR

This paper reports the most precise measurement to date of the $$ electromagnetic transition form factor slope, using a large sample of kaon decay events, confirming theoretical predictions and previous results.

Contribution

It provides the first high-precision experimental determination of the $$ transition form factor slope in the time-like region.

Findings

Measured slope parameter $a = (3.68 \u00b1 0.57) imes 10^{-2}$

Results agree with theoretical models

Most precise measurement in the time-like region

Abstract

The NA62 experiment collected a large sample of charged kaon decays in 2007 with a highly efficient trigger for decays into electrons. A measurement of the $\pi^0$ electromagnetic transition form factor slope parameter from $1.11\times10^{6}$ fully reconstructed $K^\pm \to \pi^\pm \pi^0_D, \pi^0_D \to e^+ e^-\gamma$ events is reported. The measured value $a = (3.68 \pm 0.57)\times10^{-2}$ is in good agreement with theoretical expectations and previous measurements, and represents the most precise experimental determination of the slope in the time-like momentum transfer region.