Within an extended chiral constituent quark formalism, we investigate contributions from all possible five-quark components in the octet baryons to the pion-baryon ($sigma_{pi B}$) and strangeness-baryon ($sigma_{s B}$) sigma terms; $B equiv N,~Lambd
a,~Sigma,~Xi$. The probabilities of the quark-antiquark components in the ground-state baryon octet wave functions are calculated by taking the baryons to be admixtures of three- and five-quark components, with the relevant transitions handled {it via} the $^{3}$P$_{0}$ mechanism. Predictions for $sigma_{pi B}$ and $sigma_{s B}$ obtained by using input parameters taken from the literature are reported. Our results turn out to be, in general, consistent with the findings via lattice QCD and chiral perturbation theory.
Our earlier Faddeev three-body study in the $K^-$-deuteron scattering length, $A_{K^-d}$, is revisited here in the light of the recent developments in two fronts: {it (i)} the improved chiral unitary approach to the theoretical description of the cou
pled $Kbar N$ related channels at low energies, and {it (ii)} the new and improved measurement from SIDDHARTA Collaboration of the strong interaction energy shift and width in the lowest $K^-$-hydrogen atomic level. Those two, in combination, have allowed us to produced a reliable two-body input to the three-body calculation. All available low-energy $K^-p$ observables are well reproduced and predictions for the $Kbar N$ scattering lengths and amplitudes, $(pi Sigma)^circ$ invariant-mass spectra, as well as for $A_{K^-d}$ are put forward and compared with results from other sources. The findings of the present work are expected to be useful in interpreting the forthcoming data from CLAS, HADES, LEPS and SIDDHARTA Collaborations.
A chiral constituent quark model approach, embodying s- and u-channel exchanges,complemented with a Reggeized treatment for t-channel is presented. A model is obtained allowing data for $pi^- p to eta n$ and $gamma p to eta p$ to be describe satisfac
torily. For the latter reaction, recently released data by CLAS and CBELSA/TAPS Collaborations in the system total energy range $1.6 lesssim W lesssim 2.8$ GeV are well reproduced due to the inclusion of Reggeized trajectories instead of simple $rho$ and $omega$ poles. Contribution from missing resonances is found to be negligible in the considered processes.
Within an extended chiral constituent quark model, three- and five-quark structure of the $S_{01}$ resonance $Lambda(1405)$ is investigated. Helicity amplitudes for the electromagnetic decays ($Lambda(1405) to Lambda(1116)gamma$, $Sigma(1194)gamma$),
and transition amplitudes for strong decays ($Lambda(1405)toSigma(1194)pi$, $ K^{-}p$) are drived, as well as the relevant decay widths. The experimental value for the strong decay width, $Gamma_{Lambda(1405)to (Sigma pi)^circ}=50pm 2$ MeV, is well reproduced with about 50% of five-quark admixture in the $Lambda(1405)$. Important effects due to the configuration mixings among $Lambda^{2}_{1}P_{A}$, $Lambda^{2}_{8}P_{M}$ and $Lambda^{4}_{8}P_{M}$ are found. In addition, transitions between the three- and five-quark components in the baryons turn out to be significant in both radiative and strong decays of the $Lambda(1405)$ resonance.
A formalism based on a chiral quark model ($chi$QM) approach complemented with a one-gluon exchange model, to take into account the breakdown of the $SU(6)otimes O(3)$ symmetry, is presented. The configuration mixing of wave functions for nucleon and
resonances are derived. % With few adjustable parameters, differential cross-section and polarized beam asymmetry for the $gamma p to eta p$ process are calculated and successfully compared with the data in the centre-of-mass energy range from threshold up to 2 GeV. The known resonances $S_{11}(1535)$, $S_{11}(1650)$, $P_{13}(1720)$, $D_{13}(1520)$, and $F_{15}(1680)$, as well as two new $S_{11}$ and $D_{15}$ resonances are found to be dominant in the reaction mechanism. Besides, connections among the scattering amplitudes of the $chi$QM approach and the helicity amplitudes, as well as decay widths of resonances are established. Possible contributions from the so-called missing resonances are investigated and found to be negligible.
