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Register a new userAxial charges of octet and decuplet baryons
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We present a study of axial charges of baryon ground and resonant states with relativistic constituent quark models. In particular, the axial charges of octet and decuplet $N$, $Sigma$, $Xi$, $Delta$, $Sigma^*$, and $Xi^*$ baryons are considered. The theoretical predictions are compared to existing experimental data and results from other approaches, notably from lattice quantum chromodynamics and chiral perturbation theory. The relevance of axial charges with regard to $pi$-dressing and spontaneous chiral-symmetry breaking is discussed.
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We evaluate the strangeness-conserving $N N$, $SigmaSigma$, $XiXi$, $LambdaSigma$ and the strangeness-changing $Lambda N$, $Sigma N$, $LambdaXi$, $SigmaXi$ axial charges in lattice QCD with two flavors of dynamical quarks and extend our previous work on pseudoscalar-meson-octet-baryon coupling constants so as to include $piXiXi$, $KLambdaXi$ and $KSigmaXi$ coupling constants. We find that the axial charges have rather weak quark-mass dependence and the breaking in SU(3)-flavor symmetry is small at each quark-mass point we consider.
The magnetic dipole G_M(Q^2), electric quadrupole G_E(Q^2), and Coulomb quadrupole G_C(Q^2) form factors, describing the spin-3/2 to spin-1/2 electromagnetic transitions, are investigated within the light cone QCD sum rules. The Q^2 dependence of these form factors, as well as ratios of electric quadrupole and Coulomb quadrupole form factors to the magnetic dipole form factors are studied. We also compare our results on the magnetic dipole form factor with the prediction of the covariant spectator quark model.
The self-energies of the full set of flavor SU(3) octet and decuplet baryons are computed within a relativistic chiral effective theory framework. The leading nonanalytic chiral behavior is derived for the octet and decuplet masses, and a finite-range regularization consistent with Lorentz and gauge invariance is applied to account for the finite size of the baryons. Using a four-dimensional dipole form factor, the relative importance of various meson-baryon loop contributions to the self-energies is studied numerically as a function of the dipole range parameter and meson mass, and comparison is made between the relativistic results and earlier approximations within the heavy baryon limit.
We compute the diagonal isovector axial-vector as well as induced pseudoscalar form factors of nucleon, $Sigma$ and $Xi$ baryons by employing the light-cone QCD sum rules to leading order in QCD and including distribution amplitudes up to twist 6. Extrapolating our sum-rules results to low-momentum transfers, we make a comparison with experimental and lattice-QCD results where we can achieve a nice qualitative and quantitative agreement.
Transverse densities describe the distribution of charge and current at fixed light-front time and provide a frame-independent spatial representation of hadrons as relativistic systems. We calculate the transverse densities of the octet baryons at peripheral distances b = O(M_pi^{-1}) in an approach combining chiral effective field theory (ChEFT) and dispersion analysis. The densities are represented as dispersive integrals of the imaginary parts of the baryon electromagnetic form factors in the timelike region (spectral functions). The spectral functions on the two-pion cut at t > 4 M_pi^2 are computed using relativistic ChEFT with octet and decuplet baryons in the EOMS renormalization scheme. The calculations are extended into the rho-meson mass region, using a dispersive method that incorporates the timelike pion form-factor data. The approach allows us to construct densities at distances b > 1 fm with controlled uncertainties. Our results provide insight into the peripheral structure of nucleons and hyperons and can be compared with empirical densities and lattice-QCD calculations.
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