Search results for "SCALAR"
showing 10 items of 1002 documents
Decay of axial-vector mesons into VP andPγ
2004
We propose a phenomenological Lagrangian for the decay of the SU(3) nonets of the axial-vector mesons of J{sup PC}=1{sup +-},1{sup ++} into a vector meson and a pseudoscalar constructed with tensor fields for the vector and axial-vector mesons. The formulation leads to a good reproduction of the different decay branching ratios and assuming vector meson dominance (VMD) it also leads to good results for the radiative decay of the a{sub 1} into pion and photon, and in agreement with the structure proposed in the chiral tensor formulation of radiative decay of axial-vector mesons. The two SU(3) parameters and the mixing angle of K{sub 1A} and K{sub 1B} needed to give the physical K{sub 1}(1270…
Decay of vector-vector resonances into $\gamma$ and a pseudoscalar meson
2010
We study the decay of dynamically generated resonances from the interaction of two vectors into a $\ensuremath{\gamma}$ and a pseudoscalar meson. The dynamics requires anomalous terms involving vertices with two vectors and a pseudoscalar, which renders it special. We compare our result with data on ${K}_{2}^{*+}(1430)\ensuremath{\rightarrow}{K}^{+}\ensuremath{\gamma}$ and ${K}_{2}^{*0}(1430)\ensuremath{\rightarrow}{K}^{0}\ensuremath{\gamma}$ and find a good agreement with the data for the ${K}_{2}^{*+}(1430)$ case and a width considerably smaller than the upper bound measured for the ${K}_{2}^{*0}(1430)$ meson. We also investigate the decay into ${\ensuremath{\pi}}^{+}\ensuremath{\gamma}$ …
Hidden gauge formalism for the radiative decays of axial-vector mesons
2009
24 pages, 6 tables, 11 figures.--ISI article identifier:000262979700040 .-- ArXiv pre-print avaible at:http://arxiv.org/abs/0809.0943
Two-body effects in coherent η-meson photoproduction on the deuteron in the region of theS11(1535)resonance
2001
Coherent \ensuremath{\eta}-meson photoproduction on the deuteron has been studied, where the emphasis is on the relative importance of two-body contributions from hadronic rescattering and electromagnetic meson exchange currents besides the impulse approximation. For the elementary photoproduction amplitude a coupled resonance model developed by Bennhold and Tanabe has been used that fits reasonably well with the experimental data. The rescattering effects are treated within a coupled channel approach considering the intermediate excitation of the ${P}_{11}(1440),$ ${D}_{13}(1520),$ and ${S}_{11}(1535)$ nucleon resonances. The hadronic interaction between nucleon and resonances is modeled b…
Resonances and the Weinberg-Tomozawa 56-baryon-35-meson interaction
2006
Vector meson degrees of freedom are incorporated into the Weinberg-Tomozawa (WT) meson-baryon chiral Lagrangian by using a scheme which relies on spin--flavor SU(6) symmetry. The corresponding Bethe-Salpeter approximation successfully reproduces previous SU(3)--flavor WT results for the lowest-lying s--wave negative parity baryon resonances, and it also provides some information on the dynamics of the heavier ones. Moreover, it also predicts the existence of an isoscalar spin-parity $\frac32^-$ $K^*N$ bound state (strangeness +1) with a mass around 1.7--1.8 GeV, unstable through $K^*$ decay. Neglecting d-wave KN decays, this state turns out to be quite narrow ($\Gamma \le 15$ MeV) and it mi…
sigma meson in a nuclear medium through two pion photoproduction
2003
We show theoretical results for $(\gamma, \pi^0 \pi^0)$ production on nucleons and nuclei in the kinematical region where the scalar isoscalar $\pi \pi$ amplitude is influenced by the $\sigma$ pole. The final state interaction of the pions modified by the nuclear medium produces a spectacular shift of strength of the two pion invariant mass distribution induced by the moving of the $\sigma$ pole to lower masses and widths as the nuclear density increases.
The ρ–ω splitting in constituent quark models
2009
Abstract In this Letter we present a solution to describe simultaneously the light isoscalar and isovector vector mesons in constituent quark models. In Ref. [J. Vijande, F. Fernandez, A. Valcarce, J. Phys. G 31 (2005) 481] the q q ¯ spectrum was studied in a generalized constituent quark model constrained by the NN phenomenology and the baryon spectrum. An overall good fit to the available experimental data was obtained. A major problem of this description was the relative position of the vector ω and ρ mesons. The present results improve the description of the isoscalar meson spectroscopy. They should serve as a step forward in distinguishing conventional quark model mesons from exotic st…
Relativistic nuclear structure. I. Nuclear matter.
1990
The formalism for the Dirac-Brueckner approach to the nuclear many-body problem is described including its basis in relativistic two-nucleon scattering. A family of relativistic meson-exchange potentials is constructed which (apart from the usual coupling terms for heavy mesons) apply the pseudovector (gradient) coupling for the interaction of pseudoscalar mesons (\ensuremath{\pi},\ensuremath{\eta}) with nucleons. These potentials describe low-energy two-nucleon scattering and the deuteron data accurately. Using these potentials, the properties of nuclear matter are calculated in the Dirac-Brueckner-Hartree-Fock approximation, in which the empirical nuclear matter saturation is explained qu…
Antistrange meson-baryon interaction in hot and dense nuclear matter
2014
We present a study of in-medium cross sections and (off-shell) transition rates for the most relevant binary reactions for strange pseudoscalar meson production close to threshold in heavy-ion collisions at FAIR energies. Our results rely on a chiral unitary approach in coupled channels which incorporates the $s$- and $p$-waves of the kaon-nucleon interaction. The formalism, which is modified in the hot and dense medium to account for Pauli blocking effects, mean-field binding on baryons, and pion and kaon self-energies, has been improved to implement full unitarization and self-consistency for both the $s$- and $p$-wave interactions at finite temperature and density. This gives access to i…
Unitary chiral dynamics in J/Psi decays into VPP and the role of the scalar mesons
2004
We make a theoretical study of the $\J$ decays into $\omega\pi\pi$, $\phi\pi\pi$, $\omega K \bar{K}$ and $\phi K\bar{K}$ using the techniques of the chiral unitary approach stressing the important role of the scalar resonances dynamically generated through the final state interaction of the two pseudoscalar mesons. We also discuss the importance of new mechanisms with intermediate exchange of vector and axial-vector mesons and the role played by the OZI rule in the $\J\phi\pi\pi$ vertex, quantifying its effects. The results nicely reproduce the experimental data for the invariant mass distributions in all the channels considered.