Sigma and sigma-like terms in pion weak-production near threshold

초록

The scalar and the pseudo-scalar (PS) form factors represent the scalar and the PS quark density distributions, respectively, on a nucleon due to finite quark masses, and they are directly related to the sigma term in pi - N scattering and to the sigma-like term in charged pion electro-production. We show that they manifest themselves in pion weak-productions. We also discuss how to deduce and estimate the effects of such form factors in pion weak-productions.