On the pion decay constant

TL;DR

This paper discusses the determination of the pion decay constant f_pi, highlighting its sensitivity to the pion mass used in chiral expansion given current experimental accuracy.

Contribution

It provides insights into how the experimental determination of f_pi depends on the pion mass in chiral expansion, emphasizing potential sources of uncertainty.

Findings

f_pi value is sensitive to pion mass choice

Current experimental accuracy influences f_pi determination

Comments on evaluation methods for f_pi

Abstract

The pion decay constant f_pi plays a crucial role in many areas of low energy particle physics. Its value may e.g. be deduced from experimental data on leptonic pion decays. Here, we provide comments on several aspects of this evaluation. In particular, we point out that at the present level of experimental accuracy, the value of f_pi is sensitive to the value of the pion mass chosen in its chiral expansion.