Related papers: Vector and axial-vector structures of the Theta^+
We analyze recent experimental information on the excitation of the Theta+(1540) pentaquark in the hadronic reaction pp -> p Sigma+ K0. Upon describing the conventional production process - which serves as a normalization - in a meson…
The effects of SU(3) symmetry breaking and configuration mixing have been investigated for the weak vector and axial-vector form factors in the chiral constituent quark model (\chi CQM) for the strangeness changing as well as strangeness…
The data on the reactions K^+Xe --> K^0 \gamma X and K^+Xe --> K^+ \gamma X, obtained with the bubble chamber DIANA, have been analyzed for possible radiative decays of the \Theta^+(1540) baryon: \Theta^+ --> K^0 p \gamma and \Theta^+ -->…
We report on a new measurement of the neutron beta-asymmetry parameter $A$ with the instrument \perkeo. Main advancements are the high neutron polarization of $P = 99.7(1)%$ from a novel arrangement of super mirror polarizers and reduced…
We construct a chiral lagrangian for pentaquark baryons assuming that the recently found Theta^+ (1540) state belongs to an antidecuplet of SU(3) flavor symmetry with J^P = (1/2)^(+-). We derive the Gell-Mann-Okubo formulae for the…
We analyze quark-mass and $1/N_c$ corrections to all of the radiative transitions between the vector-meson nonet and the pseudoscalar-meson nonet within a chiral effective Lagrangian approach. We perform fits of the available coupling…
We consider neutral pseudoscalar, $\eta $, and axial vector, $f_1(1420)$, mesons in the OZI-rule-respecting flavor basis, $\lbrace (\bar s s), {1\over \sqrt{2}}(\bar u u + \bar d d)\rbrace$, and suggest a scenario for their coupling to the…
We investigate the chiral structure of local vector and axial-vector tetraquark currents, and study their chiral transformation properties. We consider the charge-conjugation parity and classify all the isovector vector and axial-vector…
The exotic baryon $\Theta^+(uudd\bar{s})$ is studied with microscopic calculations in a quark model by using a method of antisymmetrized molecular dynamics(AMD). We predict narrow states, $J^\pi=1/2^+(I=0)$, $J^\pi=3/2^+(I=0)$, and…
The form factor of the vector meson V conversion transition into the pseudoscalar meson P and the lepton pair l+l- is presented for V=rho0,omega,phi and P=pi0,eta. Our approach is based on the chiral effective field theory with resonances.…
The branching fractions of the axial vector meson decays $f_1 \to a_0 \pi,\pi\pi\eta$, $f_1 \to \rho \pi,\pi\pi\pi$ and $f_1 \to KK\pi$ are calculated in the standard $U(3) \times U(3)$ quark NJL model. The intermediate channels with the…
The narrow width of the exotic narrow baryon resonance $\Theta^+$ might be explained by mixing between the two nearly degenerate states that arise in models with two diquarks and an antiquark. The only open $\Theta^+$ decay channel is $KN$.…
We present results on the nucleon axial vector form factors $G_A(q^2)$ and $G_p(q^2)$ in the quenched theory and using two degenerate flavors of dynamical Wilson fermions for momentum transfer squared from about 0.1 to about 2 GeV^2 and for…
Several recent experiments have reported evidence for a narrow baryon resonance with positive strangeness ($\Theta^+$) at a mass of 1.54 GeV/$c^2$. Baryons with $S=+1$ cannot be conventional $qqq$ states and the reports have thus generated…
The newly observed $\Theta^+$ resonance is believed to be a pentaquark with the constituent quarks $uudd\bar s$. There are a few options for the constituent quark structure. Some advocate diquark-diquark-antiquark $(ud)$-$(ud)$-$\bar s$…
The rates and spectra of the anomalous $\eta\to\pi^+\pi^-\gamma$ and $\eta' \to\pi^+\pi^-\gamma$ decays are calculated. The approach is based on the effective meson Lagrangian obtained in the Nambu-Jona-Lasinio model with vector and…
A systematic lowering in mass of strangeness ambiguous $pK^0_S$ peaks relative to the $nK^+$ is noted. We discuss how measurement of $\gamma p\to \Theta^+ K^0_S\to p K^0_S K^0_S \to p\pi^+\pi^-\pi^+\pi^-$ in association with $\gamma p\to…
Form factors and decay widths for $D^{\ast}\rightarrow D \gamma$ and $D^{\ast}\rightarrow D \pi$ decays are estimated in a relativistic constituent quark model. Relativistic corrections due to light quarks are found to be substantial and to…
We report in the present talk recent results of the tensor properties of the nucleon within the framework of the chiral quark-soliton model. The tensor and anomalous tensor magnetic form factors are calculated for the momentum transfer up…
A symmetry-preserving continuum approach to the calculation of baryon properties in relativistic quantum field theory is used to predict all form factors associated with nucleon-to-$\Delta$ axial and pseudoscalar transition currents,…