SU ( 3 ) symmetry breaking in hyperon semileptonic decays

We study the weak interaction axial form factors of the octet baryons, within the covariant spectator quark model, focusing on the dependence of four-momentum transfer squared, Q 2 . In our model the axial form factors GA(Q 2 ) (axial-vector form factor) and GP (Q 2 ) (induced pseudoscalar form factor), are calculated based on the constituent quark axial form factors and the octet baryon wave functions. The quark axial current is parametrized by the two constituent quark form factors, the axial-vector form factor g q A (Q 2 ), and the induced pseudoscalar form factor g q P (Q 2 ). The baryon wave functions are composed of a dominant S-state and a P -state mixture for the relative angular momentum of the quarks. First, we study in detail the nucleon case. We assume that the quark axial-vector form factor g q A (Q 2 ) has the same function form as that of the quark electromagnetic isovector form factor. The remaining parameters of the model, the P -state mixture and the Q 2 -dependence of g q P (Q 2 ), are determined by a fit to the nucleon axial form factor data obtained by lattice QCD simulations with large pion masses. In this lattice QCD regime the meson cloud effects are small, and the physics associated with the valence quarks can be better calibrated. Once the valence quark model is calibrated, we extend the model to the physical regime, and use the low Q 2 experimental data to estimate the meson cloud contributions for GA(Q 2 ) and GP (Q 2 ). Using the calibrated quark axial form factors, and the generalization of the nucleon wave function for the other octet baryon members, we make predictions for all the possible weak interaction axial form factors GA(Q 2 ) and GP (Q 2 ) of the octet baryons. The results are compared with the corresponding experimental data for GA(0), and with the estimates of baryon-meson models based on SU (6) symmetry.

Section: Su (3) Baryon-meson Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Axial form factors of the octet baryons in a covariant quark model

Ramalho

Tsushima

2016

“…The sub-leading terms involve (i) the recoil piece of the convection current, which is O (q/M B ), where q is the momentum transfer through the current which is At q 2 = 0 the baryon matrix elements for the vector current in the limit of exact SU (3) symmetry are simply given by the matrix elements of the associated charge or SU(3) generator. Therefore, to all orders in the 1/N c expansion [29]:…”

Section: The Baryon Vector Current At Tree Levelmentioning

confidence: 99%

“…Among the most relevant QCD operators studied in the 1/N c expansion are the Hamiltonian (baryon masses) [25,27], axial [6,7,10,23,28] and vector [29] currents and magnetic moments [8,9,28].…”

Section: Baryon Chiral Perturbation Theory In the 1/n C Expansionmentioning

confidence: 99%

Baryon vector current in the chiral and1/Ncexpansions

Flores‐Mendieta

Goity

2014

Self Cite

“…It is then possible to consider physical quantities in the large-N c limit, where corrections arise at relative orders 1/N c , 1/N 2 c and so on, which is precisely the origin of the 1/N c expansion. Applications of this formalism to the computation of static properties of baryons range from masses [5,9,10], couplings [5,9,11,12] to magnetic moments [11,13], to name but a few.…”

Section: Introductionmentioning

confidence: 99%

Renormalization of the baryon axial vector current in large-Ncchiral perturbation theory

Flores‐Mendieta

Hofmann

2006

Self Cite

The baryon axial vector current is computed at one-loop order in heavy baryon chiral perturbation theory in the large-Nc limit, where Nc is the number of colors. Loop graphs with octet and decuplet intermediate states cancel to various orders in Nc as a consequence of the large-Nc spin-flavor symmetry of QCD baryons. These cancellations are explicitly shown for the general case of N f flavors of light quarks. In particular, a new generic cancellation is identified in the renormalization of the baryon axial vector current at one-loop order. A comparison with conventional heavy baryon chiral perturbation theory is performed at the physical values Nc = 3, N f = 3.