Three pion nucleon coupling constants

Abstract

There exist four pion nucleon coupling constants, [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] which coincide when up and down quark masses are identical and the electron charge is zero. While there is no reason why the pion–nucleon–nucleon coupling constants should be identical in the real world, one expects that the small differences might be pinned down from a sufficiently large number of independent and mutually consistent data. Our discussion provides a rationale for our recent determination [Formula: see text] based on a partial wave analysis of the [Formula: see text] self-consistent nucleon–nucleon Granada-2013 database comprising 6713 published data in the period 1950–2013.