A diquark model for baryons containing one heavy quark

We present a phenomenological ansatz for coupling a heavy quark with two light quarks to form a heavy baryon. The heavy quark is treated in the heavy mass limit, and the light quark dynamics is approximated by propagating scalar and axial vector ??diquarks??. The resulting effective lagrangian, which incorporates heavy quark and chiral symmetry, describes interactions of heavy baryons with Goldstone bosons in the low energy region. As an application, the Isgur-Wise form factors are estimated.     

A relativistic quark model for baryons

The Bethe-Salpeter equation for the relativistic three quark bound state is solved for an instantaneous interaction in the ladder approximation. The particular solution obtained is valid for simple potentials in both the weak and strong binding situations. The general method for calculating matrix elements for the interaction of the bound state with an external electromagnetic field is presented. Particular attention is paid to the emergence of the nonrelativistic quark model interaction as the lowest order approximation in a perturbative expansion in the inverse quark mass. Relativistic corrections to this approximation are investigated, and their importance is seen to depend on the quark mass. For light quarks these corrections can be large, and to reproduce the proton magnetic moment, for instance, a substantial anomalous moment is necessary. The model has several encouraging features. The form factors with a harmonic potential have an asymptotic k^?2 behavior, and the relativistic corrections to the SU(6) results for the form factors are of the correct order of magnitude.     

Triply heavy baryons in the constituent quark model

The constituent quark model is used to compute the ground and excited state masses of QQQ baryons containing either c or b quarks.The quark model parameters previously used to describe the properties of charmonium and bottomonium states were used in this analysis.The non-relativistic three-body bound state problem is solved by means of the Gaussian expansion method which provides sufficient accuracy and simplifies the subsequent evaluation of the matrix elements.Several low-lying states with quantum numbers J^P=1/2^±,3/2^±,5/2^±and 7/2^+are reported.We compare the results with those obtained by the other theoretical formalisms.There is a general agreement for the mass of the ground state in each sector of triply heavy baryons.However,the situation is more puzzling for the excited states,and appropriate comments about the most relevant features of our comparison are given.     

Properties of doubly heavy baryons in the relativistic quark model

Mass spectra and semileptonic decay rates of baryons consisting of two heavy (b or c) and one light quark are calculated in the framework of the relativistic quark model. The doubly heavy baryons are treated in the quark-diquark approximation. The ground and excited states of both the diquark and quark-diquark bound systems are considered. The quark-diquark potential is constructed. The light quark is treated completely relativistically, while the expansion in the inverse heavy-quark mass is used. The weak transition amplitudes of heavy diquarks bb and bc going, respectively, to bc and cc are explicitly expressed through the overlap integrals of the diquark wave functions in the whole accessible kinematic range. The relativistic baryon wave functions of the quark-diquark bound system are used for the calculation of the decay matrix elements, the Isgur-Wise function, and decay rates in the heavy-quark limit.     

Diquark structure in heavy quark baryons in a geometric model

Using a geometric model to study the structure of hadrons, baryons having one, two and three heavy quarks have been studied here. The study reveals diquark structure in baryons with one and two heavy quarks but not with three heavy identical quarks.     

Covariant quark model for the baryons

A family of simply solvable covariant quark models for the baryons is presented. With optimal parameter choices the models reproduce the empirical spectra of the baryons in all flavor sectors to an accuracy of a few percent. Complete spectra are obtained for all states of the strange, charm and beauty hyperons with L ⩽2. The magnetic moments and axial coupling constants of the ground state baryons correspond to those of conventional quark models. We construct current-density operators tjat are consistent with empirical nucleon form factors at low and medium momenta.     

Mass spectra of heavy baryons in the relativistic quark model

The mass spectra of the ground state and excited heavy baryons consisting of two light (u, d, s) and one heavy (c, b) quarks are calculated. The heavy-quark-light-diquark picture is used within the relativistic quark model. An overall good agreement of the obtained predictions with available experimental data is found. The text was submitted by the authors in English.     

Radiative decays of heavy baryons with heavy quark symmetry

The decay widths for the radiative decays of heavy baryons are calculated in the heavy quark effective theory. Introducing the interpolating fields for heavy baryons we obtain the transition matrix elements and the corresponding decay widths. Considering theSU(6) flavor-spin wave functions for heavy baryons, the coupling constants are calculated in the nonrelativistic quark model. Since the masses of the heavy baryons are not available, we have taken the predicted bag model masses. We find our results are quite different from that of the heavy quark bag model calculations.     

A non-relativistic quark model for baryons with pion cloud

We incorporate chiral invariance into a non-relativistic scheme for baryon structure in an approximate way, by introducing additional mesonic degrees of freedom. We proceed to calculate static properties for the nucleon and isobar. Using standard few-body techniques we are able to eliminate center-of-mass spurious motion from the wave functions. In our scheme a D-state admixture arises in the nucleon and isobar wave functions. There are parametrizations compatible with sphericity leading to a strong quenching of the effective quark axial coupling constant. Others lead to deformed ground-state baryons with almost no quenching of the weak-coupling constant.     

B meson decays to baryons in the diquark model

We study B meson decays to two charmless baryons in the diquark model, including strong and electroweak penguins as well as the tree operators. It is shown that penguin operators can enhance considerably, but affect only slightly, where and are non-strange and strange baryons, respectively. The dependence of the decay rates due to tree–penguin interference is illustrated. In principle, some of the modes could dominate over for , but in general the effect is milder than their mesonic counterparts. This is because the operator can only produce vector but not scalar diquarks, while the opposite is true for and . Predictions from the diquark model are compared to those from the sum rule calculation. The decays and inclusive baryonic decays are also discussed. Received: 27 December 2001 / Published online: 5 April 2002     

Light and heavy hadron masses in a relativistic quark potential model with diquark clustering

Meson masses are calculated in the quark model with a phenomenological spin-dependent potential of form motivated by QCD. For comparison, the potential is used in two different wave equations, both of which incorporate the feature of relativistic two-body kinematics. The masses of light and heavy pseudoscalar and vector mesons are calculated in the model with only a small number of adjustable parameters, and good qualitative agreement with experiment is obtained. The masses of diquarks are calculated without any additional parameters, using the same potential as for mesons except for a QCD color factor. Then baryon masses are calculated, also without additional parameters, in an approximation in which a baryon is a composite of a quark and a diquark. Again the results are in good qualitative agreement with experiment. Both wave equations yield similar solutions, although there are differences in detail. One distinctive feature of the model is that quark current masses are used as input, and effective constituent quark masses are obtained as a result of the calculation.     

Heavy baryons in the relativistic quark model

We present a summary of results for exclusive decays of single and double heavy-flavored baryons in the relativistic three-quark model.     

Charmed baryons in a relativistic quark model

We calculate mass spectra of charmed baryons within a relativistically covariant quark model based on the Bethe-Salpeter equation in instantaneous approximation. Interactions are given by a linearly rising three-body confinement potential and a flavor-dependent two-body force derived from QCD instanton effects. This model has already been successfully applied to the calculation of light flavor baryon spectra and is now extended to heavy baryons. Within the same framework we compare the results to those obtained with the more conventional one-gluon exchange potential.     

Heavy baryons in the relativistic quark model

In the framework of the relativistic quasipotential quark model the mass spectrum of baryons with two heavy quarks is calculated. The quasipotentials for interactions of two quarks and of a quark with a scalar and axial vector diquark are evaluated. The bound state masses of baryons with are computed.     

An application of a heavy quark bag model to non-leptonic decays of charmed baryons

Non-leptonic decays of lower mass charmed baryons are calculated by employing the QCD corrected weak Hamiltonian and wave functions of a heavy quark bag model. Baryon matrix elements of the parity violating part of the charmchanging weak Hamiltonian are included, too. The results for the partial widths Γ and asymmetry parameters α are compared with the results of other models and with experiments.     

Static properties and semileptonic decays of doubly heavy baryons in a nonrelativistic quark model

We evaluate static properties and semileptonic decays for the ground state of doubly heavy Ξ, Ξ', Ξ ^* and Ω, Ω', Ω ^* baryons. Working in the framework of a nonrelativistic quark model, we solve the three-body problem by means of a variational ansatz made possible by heavy-quark spin symmetry constraints. To check the dependence of our results on the inter-quark interaction we use five different quark-quark potentials that include a confining term plus Coulomb and hyperfine terms coming from one-gluon exchange. Our results for static properties (masses, charge radii and magnetic moments) are, with a few exceptions for the magnetic moments, in good agreement with a previous Faddeev calculation. Our much simpler wave functions are used to evaluate semileptonic decays of doubly heavy Ξ, Ξ'(J = 1/2) and Ω, Ω'(J = 1/2) baryons. Our results for the decay widths are in good agreement with calculations done within a relativistic quark model in the quark-diquark approximation. An erratum to this article is available at .