Eta --> 3 pi and quark masses

Abstract

In recent years, the decay eta --> 3 pi has received considerable attention from experimental and theoretical side. It is of particular theoretical interest because it allows for the determination of (m_u - m_d). In addition, for many years now theory has had difficulties to understand the slope of the neutral channel Dalitz plot distribution, which in contrast is very well measured. I discuss here the relation of the decay to the masses of the light quarks and review a number of theoretical and experimental works that are concerned with these questions.

Comments: 15 pages, 5 figures, plenary talk presented at The 7th International Workshop on Chiral Dynamics, August 6 -10, 2012, Jefferson Lab, Newport News, Virginia, USA