Hara's theorem in the constituent quark model.

Abstract

We show that the parity-violating electromagnetic matrix elements describing the hyperon decay in the nonrelativistic constituent quark model obey Hara{close_quote}s theorem in first-order perturbation theory, i.e., to {ital O}({ital G}{sub {ital F}}), where {ital G}{sub {ital F}}{approx_equal}10{sup {minus}5}{ital M}{sub {ital N}}{sup {minus}2} is the Fermi weak interaction coupling constant and {ital M}{sub {ital N}} is the nucleon mass. Particular emphasis is put on questions of gauge invariance and of threshold behavior. We discuss our results and compare them with the literature. {copyright} {ital 1996 The American Physical Society.}