Determination of the light quark masses from eta -\rightarrow 3 pi

2012

Recently, several experimental collaborations have invested considerable effort into new and more precise measurements of the η ! 3π decays. These experimental advances require revisiting the corresponding theoretical analyses. In this work, we present a new calculation of the η ! 3π decay amplitude relying on dispersive methods. We show how the study of this decay allows one to extract a fundamental parameter of the Standard Model, namely the quark mass ratio Q 2 � (m 2 − ˆ m 2 )/(m 2 − m 2), with good precision. We find Q = 21.3� 0.6. We then discuss the