Search results for "quark model"
showing 10 items of 207 documents
Quark model description of the tetraquark stateX(3872)in a relativistic constituent quark model with infrared confinement
2010
We explore the consequences of treating the $X(3872)$ meson as a tetraquark bound state. As dynamical framework we employ a relativistic constituent quark model which includes infrared confinement in an effective way. We calculate the decay widths of the observed channels $X\ensuremath{\rightarrow}J/\ensuremath{\psi}+2\ensuremath{\pi}(3\ensuremath{\pi})$ and $X\ensuremath{\rightarrow}{\overline{D}}^{0}+{D}^{0}+{\ensuremath{\pi}}^{0}$ via the intermediate off-shell states $X\ensuremath{\rightarrow}J/\ensuremath{\psi}+\ensuremath{\rho}(\ensuremath{\omega})$ and $X\ensuremath{\rightarrow}\overline{D}+{D}^{*}$. For reasonable values of the size parameter ${\ensuremath{\Lambda}}_{X}$ of the $X(3…
A quark model analysis of the transversity distribution
1997
The feasibility of measuring chiral-odd parton distribution functions in polarized Drell-Yan and semi-inclusive experiments has renewed theoretical interest in their study. Models of hadron structure have proven succesful in describing the gross features of the chiral-even structure functions. Similar expectations support our study of the transversity parton distributions in the Isgur-Karl and MIT bag models. We confirm the diverse low x behavior of the transversity and spin structure functions at the experimental scale and show that it is fundamentally a consequence of the different behavior under evolution of these functions. The inequalities of Soffer establish constraints between data a…
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.
Re-analysis of theΛ(1520)photoproduction reaction
2014
Based on previous studies that support the important role of the N*(2120)D-13 resonance in the gamma p -> K+ A(1520) reaction, we make a re-analysis of this A(1520) photoproduction reaction taking into account the recent CLAS differential cross-section data. In addition to the contact, t-channel (K) over bar exchange, s-channel nucleon pole, and N*(2120) [previously called N*(2080)] resonance contributions, which have been considered in previous works, we also study the u-channel A(1115) hyperon pole term. The latter mechanism has always been ignored in all theoretical analysis, which has mostly relied on the very forward K+ angular LEPS data. It is shown that when the contributions from th…
The baryonic spectrum in a constituent quark model including a three-body force
1992
We analyze, within a non-relativistic quark model, the low energy part of the baryonic spectrum in the octet and decuplet flavour representations. The relevance of a strong Coulomb potential is emphasized in order to explain its general features. The addition of a three-body force allows to solve the ‘Roper puzzle’, giving a consistent explanation to its relative position in the spectrum.
Exclusive nonleptonic decays of bottom and charm baryons in a relativistic three-quark model: Evaluation of nonfactorizing diagrams
1998
Exclusive nonleptonic decays of bottom and charm baryons are studied within a relativistic three-quark model with a Gaussian shape for the momentum dependence of the baryon-three-quark vertex. We include factorizing as well as nonfactorizing contributions to the decay amplitudes. For heavy-to-light transitions Q -> q u d the total contribution of the nonfactorizing diagrams amount up to approximately 60% of the factorizing contributions in amplitude, and up to approximately 30% for b -> c u d transitions. We calculate the rates and the polarization asymmetry parameters for various nonleptonic decays and compare them to existing data and to the results of other model calculations.
Heavy-to-light semileptonic decays ofΛbandΛcbaryons in the covariant confined quark model
2014
We present a detailed analysis of the heavy-to-light semileptonic decays of theb andc baryons �b → pl ¯ νl andc → nl + νl in the covariant confined quark model. We calculate the invariant and helicity amplitudes of the two processes which are then used to analyze their angular decay distributions, their rates and asymmetry parameters.
Adiabaticity and color mixing in tetraquark spectroscopy
2013
We revisit the role of color mixing in the quark model calculation of tetraquark states, and compare simple pairwise potentials to more elaborate string models with three-and four-body forces. We attempt to disentangle the improved dynamics of confinement from the approximations made in the treatment of the internal color degrees of freedom.
ΛNNandΣNNsystems at threshold. II. The effect ofDwaves
2007
Using the two-body interactions obtained from a chiral constituent quark model, we study allN N andN N states with I = 0, 1, 2a ndJ = 1/2, 3/2 at threshold, taking into account all three-body configurations with S and D wave components. We constrain further the limits for theN spin-triplet scattering length a1/2,1 .U sing the hypertriton binding energy, we find a narrow interval for the possible values of theN spin-singlet scattering length a1/2,0. We find that theN N system has a quasibound state in the (I,J ) = (1, 1/2) channel very near threshold with a width of about 2.1 MeV.
Flavor-changing decays of theZ0and leptoquarks
1989
Many extensions of the standard model, e.g., certain composite models and some superstring- inspired'' E{sub 6} models, contain new scalar matter fields which couple to both quarks and leptons, i.e., leptoquarks. We consider leptonic flavor-changing decays of the {ital Z}{sup 0}, e.g., {ital Z}{sup 0}{r arrow}{mu}{sup +}{tau}{sup {minus}}, due to one-loop diagrams involving such leptoquarks. We find branching ratios which are at most {approx}10{sup {minus}7}, even assuming generous values for unknown Yukawa couplings.