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Once-Subtracted Dispersion Relations, Current Algebra, and Nonleptonic Weak Decays of Hyperons

K. J. Sebastian

  • Lowell Technological Institute, Lowell, Massachusetts, 01854

Phys. Rev. D 4, 771 – Published 1 August, 1971

DOI: https://doi.org/10.1103/PhysRevD.4.771

Abstract

Nonleptonic weak decays of hyperons and the K12π decay are carefully analyzed using current algebra, partial conservation of axial-vector current, and once-subtracted dispersion relations, a method suggested by Okubo, Mathur, and Marshak. We have calculated the dispersion integral by assuming it to be saturated by the low-mass intermediate states of the nucleon octet, of the 32+ decuplet of Δ(1236), and of the ½ SU3 singlet Y0*(1405), in the case of hyperon decays, and by the intermediate states of vector mesons and a possible 0+ scalar-meson nonet, in the case of K12π decay. The matrix element of the parity-violating weak Hamiltonian density between two baryons (which is required to evaluate the hyperon decay amplitudes) is related to the K12π decay amplitude by the K1 tadpole mechanism. With pseudovector SU3-symmetric coupling among the nucleon and pseudoscalar-meson octets, we are able to obtain a good fitting of all the hyperon decay amplitudes in terms of four parameters. We also find that the corrections to the soft-pion values are very important not only for P-wave hyperon decay amplitudes, but also for S-wave amplitudes. They are also extremely important for K12π decays. Furthermore, we find that, contrary to the findings of Hara and Nambu, there is no evidence for the concept of a "universal parityconserving spurion" in hyperon and K12π weak decays.

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