Selection rules for production and η-π decays of odd-CP exotics

Abstract

Statements and conditions of validity are presented for three selection rules relevant to the analysis of data indicating the existence of a possible CP-exotic state and to the determination of whether it is a four-quark or hybrid state. SU(3) flavor symmetyry forbids the decay of an odd-CP SU(3)-octet state into two octet pseudoscalar mesons. Isospin symmetry forbids the ηπ decay of an odd-parity hybrid state via an OZI-allowed diagram. No selection rule forbids the ηπ decay of a four-quark state. All n-point functions in which there are an odd number of particles with unnatural parity, all momental lying in the same plane and all particles with spin having zero helicity, are forbidden by angular momentum and parity conservation.