First Lattice QCD Study of the Sigma -> n Axial and Vector Form Factors with SU(3) Breaking Corrections

Abstract

We present the first quenched lattice QCD study of the form factors relevant for the hyperon semileptonic decay Sigma -> n l nu. The momentum dependence of both axial and vector form factors is investigated and the values of all the form factors at zero-momentum transfer are presented. Following the same strategy already applied to the decay K0 -> pi- l nu, the SU(3)-breaking corrections to the vector form factor at zero-momentum transfer, f1(0), are determined with great statistical accuracy in the regime of the simulated quark masses, which correspond to pion masses above ~ 0.7 GeV. Besides f1(0) also the axial to vector ratio g1(0) / f1(0), which is relevant for the extraction of the CKM matrix element Vus, is determined with significant accuracy. Due to the heavy masses involved, a polynomial extrapolation, which does not include the effects of meson loops, is performed down to the physical quark masses, obtaining f1(0) = -0.948 +/- 0.029 and g1(0) / f1(0) = -0.287 +/- 0.052, where the uncertainties do not include the quenching effect. Adding a recent next-to-leading order determination of chiral loops, calculated within the Heavy Baryon Chiral Perturbation Theory in the approximation of neglecting the decuplet contribution, we obtain f1(0) = -0.988 +/- 0.029(lattice) +/- 0.040(HBChPT). Our findings indicate that SU(3)-breaking corrections are moderate on both f1(0) and g1(0). They also favor the experimental scenario in which the weak electricity form factor, g2(0), is large and positive, and correspondingly the value of |g1(0) / f1(0)| is reduced with respect to the one obtained with the conventional assumption g2(q**2) = 0 based on exact SU(3) symmetry.

arXiv commentfinal version to appear in Nucl. Phys. B

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• Recent developments in SU(3) covariant baryon chiral perturbation theory
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• Chiral Corrections to the Hyperon Vector Form Factors
• Weak vector and axial-vector form factors in the chiral constituent quark model with configuration mixing
• Hyperon decay form factors in chiral perturbation theory
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• Testing SU(3) Flavor Symmetry in Semileptonic and Two-body Nonleptonic Decays of Hyperons
• Hyperon vector form factor from 2+1 flavor lattice QCD
• Renormalization of the baryon axial vector current in large-N_c chiral perturbation theory: Effects of the decuplet-octet mass difference and flavor symmetry breaking
• Hyperon semileptonic decays in QCD sum rules
• SU(3) breaking in hyperon transition vector form factors
• Continuum limit of hyperon vector coupling $f_1(0)$ from 2+1 flavor domain wall QCD
• The baryon vector current in the combined chiral and 1/Nc expansions
• Hyperon Physics from Lattice QCD
• Chiral Effective Theory Methods and their Application to the Structure of Hadrons from Lattice QCD
• Chiral extrapolation and finite-volume dependence of the hyperon vector couplings
• Patterns of flavour symmetry breaking in hadron matrix elements involving u, d and s quarks
• Feynman--Hellmann approach to transition matrix elements and quasi-degenerate energy states
• Baryon axial vector current in large-$N_c$ chiral perturbation theory: Complete analysis for $N_c=3$
• Properties of hyperons in chiral perturbation theory
• ${\Sigma }^{+}\to p{\ell }^{+}{\ell }^{-}$ decays within the standard model and beyond
• Hyperon Form Factors from N_f=2+1 QCD
• The effects of flavour symmetry breaking on hadron matrix elements
• Baryons and baryoniums in the perspective of QCD sum rules
• Properties of the ground-state baryons in chiral perturbation theory
• Study of vector and axial-vector form factors and the decay parameters for the semileptonic hyperon decays