Hyperon Weak Radiative Decay

Abstract

We revisit the hyperon weak radiative decays in the framework of the non-relativistic constituent quark model. This study confirms the nonlocal feature of the hyperon weak radiative transition operators which are dominated by the pole terms, and an overall self-consistent description of the available experimental data for the Cabibbo-favored hyperon weak radiative decays is achieved. It provides a natural mechanism for evading the Hara theorem, where sizeable parity-violating contributions can come from the intermediate orbital excitations. Cancellations between pole terms also explain significant SU(3) flavor symmetry breaking manifested by the experimental data. We also discuss several interesting selection rules arising from either the electromagnetic or the weak interaction vertices. These features suggest nontrivial relations among different hyperon decays.

Revisiting Weak Radiative Decays of Hyperons

“…One can convince oneself (see eg. [8]) that the A µ ψf σ µν γ 5 ψ i (A µ ψf γ µ γ 5 ψ i ) expressions correspond to the subtraction (addition) of the amplitudes relevant for the two time orderings (the A and B amplitudes of [2]). Thus, if the two resulting possibilities for the total p.v.…”

“…In the subsequent Section 4 the results of the old VMD and some quark model calculations are compared with those of ref. [2]. In this Section a thorough discussion and our views on the results of [2] are also presented.…”

“…[2]. In this Section a thorough discussion and our views on the results of [2] are also presented. In particular, it is pointed out that the observed negative sign of the (experimentally sizable) Ξ 0 → Λγ asymmetry (a symmetry-related counterpart of Σ + → pγ) does not constitute a telltale and unquestionable sign of a Hara's theorem satisfying approach.…”

“…Spurred by these experimental developments, a new round of discussion on WRHD is to be expected (see eg. [1,2,3]). In particular, paper [2] adresses the issue in the framework of the non-relativistic constituent quark model, used to evaluate the weak and electromagnetic transitions relevant for their incorporation into the baryonic pole model.…”

“…In particular, paper [2] adresses the issue in the framework of the non-relativistic constituent quark model, used to evaluate the weak and electromagnetic transitions relevant for their incorporation into the baryonic pole model. The authors of paper [2] argue that the 1/2 − pole terms provide a natural mechanism for evading Hara's theorem [4], thus explaining the large negative asymmetry observed in the Σ + → pγ decay. As it is the issue of Hara's theorem that divides the (often very respectable) authors of various WRHD papers into two opposing camps (ie.…”