Hyperon semileptonic decays and quark spin content of the proton

Abstract

We investigate the hyperon semileptonic decays and the quark spin content of the proton $\Delta \Sigma$ taking into account flavor SU(3) symmetry breaking. Symmetry breaking is implemented with the help of the chiral quark-soliton model in an approach, in which the dynamical parameters are fixed by the experimental data for six hyperon semileptonic decay constants. As a result we predict the unmeasured decay constants, particularly for $\Xi^0 \to \Sigma^+$, which will be soon measured and examine the effect of the SU(3) symmetry breaking on the spin content $\Delta \Sigma $ of the proton. Unfortunately large experimental errors of $\Xi^-$ decays propagate in our analysis making $\Delta \Sigma$ and $\Delta s$ practically undetermined. We conclude that statements concerning the values of these two quantities, which are based on the exact SU(3) symmetry, are premature. We stress that the meaningful results can be obtained only if the experimental errors for the $\Xi$ decays are reduced.Comment: The final version accepted for publication in Phys. Rev. D. 18 pages, RevTex is used with 4 figures include

Strong QCD from Hadron Structure Experiments

“…• Mass spectra of the SU(3) baryons [546,547] • Electromagnetic form factors of the baryon octet and decuplet [548][549][550][551] • Transition magnetic moments of the SU(3) baryons [552] • Axial-vector form factors of the baryon octet and decuplet [553,554] • Parity violation and Strange vector form factors of the nucleon [555][556][557] • Tensor charges and tensor form factors of the nucleon [558][559][560][561][562] • Gravitational form factors of the nucleon [563] • Semileptonic hyperon decays [564][565][566] • Unpolarized quark distributions (twist-2) of the nucleon [536,567] • Transversity distributions of the nucleon [568] • Antiquark distributions and unpolarized flavor asymmetry [569] • Quasi-parton distributions of the nucleon [570] • Electromagnetic form factors of singly heavy baryons [571,572] • Excited Ω c s as exotic baryons [573,574] • Generalized parton distributions [575] Possible extensions of the χQSM The present version of the χQSM is mainly applicable to the lowest-lying baryons. In order to explain the mass spectra and properties of both the excited light and heavy baryons, we have to extend the mean-field approximation.…”

Hyperon semileptonic decay constants with flavor SU(3) symmetry breaking

“…In a χSM, the collective operators for the HSD vector and axial-vector constants can be expressed in terms of the SU(3) Wigner D functions [20,36,37]:…”

“…Flavor SU(3) symmetry breaking in HSDs was also investigated within the 1/N c expansion [19]. In the chiral quark-soliton model (χQSM) with a model-independent approach considered, the HSD constants were investigated many years ago [20]. Being distinguished from the self-consistent χQSM [21,22], almost all dynamical parameters were fixed by using the experimental data of the masses and the HSD constants for the baryon octet in this model-independent approach.…”

Axial-vector form factors of the nucleon within the chiral quark-soliton model and their strange components

“…In fact, axialvector properties of the nucleon have to some extent already been studied in the SU (2) and SU(3) χQSM, previously [32,33,34,35,36,37,38,39,40]. However, these studies were not complete and some of them did not use the symmetry conserving quantization method [30], which guarantees that the Gell-Mann-Nishijima relations are obeyed.…”