Search results for "quark model"
showing 10 items of 207 documents
Charged charmonium molecules
2010
We make use of a self-consistent quark-model based study of four-quark charmonium-like states to interpret recent charmonium experimental data. We conclude that there exists a ${D}^{*}{\overline{D}}^{*}$ meson-meson molecule with quantum numbers $({I}^{G}){J}^{PC}=({1}^{\ensuremath{-}}){2}^{++}$. Our study confirms the presence of charged charmonium-like resonances on the excited charmonium spectrum. We find support from recent experimental data by the Belle Collaboration [R. Mizuk et al. (Belle Collaboration), Phys. Rev. D 78, 072004 (2008)]. Confirmation of the experimental data by the Belle Collaboration and the determination of the quantum numbers of the new structures would help in dis…
Physical observables in the decay Λb→Λc(→Λ+π)+τ−+ν̄τ
2015
We analyze the tauonic semileptonic baryon decays [Formula: see text] with particular emphasis on the lepton helicity flip contributions which vanish for zero lepton masses. We calculate the total rate, differential decay distributions, the longitudinal and transverse polarization components of the [Formula: see text] and the [Formula: see text], and the lepton-side forward-backward asymmetries. We use the covariant confined quark model to provide numerical results on these observables.
One-Pion Charm Baryon Transitions in a Relativistic Three-Quark Model
1998
We study one-pion transitions between charm baryon states in the framework of a relativistic three-quark model. We calculate the charm baryon-pion coupling factors that govern the S-wave, P-wave and D-wave one-pion transitions from the s-wave and the lowest lying p-wave charm baryon states down to the s-wave charm baryon states. For these we obtain: g_{\Sigma_c\Lambda_c\pi}=8.88 GeV^{-1}, f_{\Lambda_{c1}\Sigma_c\pi}=0.52 and f_{\Lambda_{c1}^*\Sigma_c\pi}=21.5 GeV^{-2}. We compare our rate predictions for the one-pion transitions with experimental results.
Semileptonic decays of theBcmeson
2001
We study the semileptonic transitions ${B}_{c}\ensuremath{\rightarrow}{\ensuremath{\eta}}_{c},$ $J/\ensuremath{\psi},$ D, ${D}^{*},$ B, ${B}^{*},$ ${B}_{s},$ ${B}_{s}^{*}$ in the framework of a relativistic constituent quark model. We use experimental data on leptonic $J/\ensuremath{\psi}$ decay, lattice and QCD sum rule results on leptonic ${B}_{c}$ decay, and experimental data on radiative ${\ensuremath{\eta}}_{c}$ transitions to adjust the quark model parameters. We compute all form factors of the above semileptonic ${B}_{c}$ transitions and give predictions for various semileptonic ${B}_{c}$ decay modes including their $\ensuremath{\tau}$ modes when they are kinematically accessible. Th…
Threshold pion photoproduction in a light-cone quark model
1991
Abstract The instantaneous and seagull graphs are calculated for pion photoproduction in a relativistic light-cone model of the nucleon. In both pseudoscalar and pseudovector coupling we find the ratios A (−) : A (0) : A (+) = 1: ( −1 2 μ):( −9 5 μ) in the nonrelativistic limit. These results correspond to the sum of seagull and Z -graph in the nonrelativistic quark model. In pseudovector coupling also the numerical results for realistic-model parameters are close to those values.
J/ψ dissociation cross sections in a relativistic quark model
2003
We calculate the amplitudes and the cross sections of the charm dissociation processes J/\psi \pi => D \bar D, D* \bar D, D \bar D*, D* \bar D* within a relativistic constituent quark model. We consistently account for the contributions coming from both the box and triangle diagrams that contribute to the dissociation processes. The cross section is dominated by the D* \bar D and D* \bar D* channels. When summing up the four channels we find a maximum total cross section of about 2.3 mb at sqrt(s) \approx 4.1 GeV. We compare our results to the results of other model calculations.
A SU(4) circle times O(3) scheme for nonstrange baryons
2007
4 pages, 3 tables.-- PACS nrs.: 12.39.Jh, 14.20.-c, 14.20.Gk.-- ISI Article Identifier: 000245667300027.-- ArXiv pre-print available at: http://arxiv.org/abs/hep-ph/0610257
A quark model analysis of Orbital Angular Momentum
1999
Orbital Angular Momentum (OAM) twist-two parton distributions are studied. At the low energy, hadronic, scale we calculate them for the relativistic MIT bag model and for non-relativistic potential quark models. We reach the scale of the data by leading order evolution using the OPE and perturbative QCD. We confirm that the contribution of quarks and gluons OAM to the nucleon spin grows with $Q^2$, and it can be relevant at the experimental scale, even if it is negligible at the hadronic scale, irrespective of the model used. The sign and shape of the quark OAM distribution at high $Q^2$ may depend strongly on the relative size of the OAM and spin distributions at the hadronic scale. Sizeab…
Screened potential and the baryon spectrum
2003
We show that in a quark model scheme the use of a screened potential, suggested by lattice QCD, instead of an infinitely rising one with the interquark distance, provides a more adequate description of the high-energy baryon spectrum. In particular an almost perfect parallelism between the predicted and observed number of states comes out throwing new light about the so-called missing resonance problem.
Magnetic moments of heavy baryons in the relativistic three-quark model
2006
The magnetic moments of ground state single, double and triple heavy baryons containing charm or bottom quarks are calculated in a relativistic three-quark model, which, in the heavy quark limit, is consistent with Heavy Quark Effective Theory and Heavy Hadron Chiral Perturbation Theory. The internal quark structure of baryons is modeled by baryonic three-quark currents with a spin-flavor structure patterned according to standard covariant baryonic wave functions and currents used in QCD sum rule calculations.