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.     

Quarks and diquarks in a baryon string model

Chew-Frautschi plots are found for baryons containing a quark and a diquark at the extremities of a relativistic string. The quark fields are modelled on free Dirac fields restricted to the ends of the string. Quantum numbers for the diquark field are obtained by adding those for two individual quark fields.The leading trajectory for the quark-diquark configuration is found to be energetically more favourable than the leading trajectories for the linear and Y-shaped baryon configurations considered previously.     

Mass spectra and wave functions of the doubly heavy baryons with J~P=1~+ heavy diquark cores

Mass spectra and wave functions of the doubly heavy baryons are computed assuming that the two heavy quarks inside a baryon form a compact heavy 'diquark core' in a color anti-triplet,and bind with the remaining light quark into a colorless baryon.The two reduced two-body problems are described by the relativistic Bethe-Salpeter equations(BSEs) with the relevant QCD inspired kernels.We focus on the doubly heavy baryons with 1~+ heavy diquark cores.After solving BSEs in the instantaneous approximation,we present the mass spectra and the relativistic wave functions of the diquark cores,and of the low-lying baryon states J~P=(1/2)~+ and(3/2)~+ with flavors(ccq)(bcq)and(bbq).A comparison with other approaches is also made.     

A diquark model for baryon spectroscopy

A quark-diquark approximation is used to investigate the mass spectroscopy of the spin-1/2 baryons belonging to theSU(3)-flavor group in a nonrelativistic potential approach. The baryon spectra obtained are confronted with relativistic results and experimental data. Root-mean-square radii are also calculated.     

Spectroscopy of doubly heavy baryons

Within a nonrelativistic quark model featuring a QCD-motivated Buchmüller-Tye potential, the mass spectra for the families of doubly heavy baryons are calculated by assuming the quark-diquark structure of the baryon wave functions and by taking into account spin-dependent splitting. Physically motivated evidence that, in the case where heavy quarks have identical flavors, quasistationary excited states may be formed in the heavy-diquark subsystem is analyzed.     

Charmed Baryon in Diquark Model

A diquark model is used to investigate single-charmed baryons.In this model,baryon is composed of two diquarks and an antiquark.Masses of lowest lying states with J~P=1/2~(±) are obtained.Baryons in our results are as heavy as other theoretic predictions and we suggest that the five-quark components should be considered in any three-quark model for studying the charmed baryons.     

Quark-diquark approximation of the three-quark structure of baryons in the quark confinement model

Octet (1/2⁺) and decuplet (3/2⁺) baryons as relativistic three-quark states are investigated using the quark confinement model (QCM), the relativistic quark model, based on some assumptions about hadronization and quark confinement. The quark-diquark approximation of the three-quark, structure of baryons is proposed. In the framework of this approach, the main low-energy characteristics of baryons, such as magnetic moments, electromagnetic radii and form factors, the ratio of axial and vector constants in semileptonic baryon decays, strong form factors and decay widths, are described. The obtained results agree with experimental data.     

Baryon magnetic moments in quark-diquark model

The baryon magnetic moments in quark-diquark model are studied and it is found that the diquark (spin 1 and 0) mixing which may arise as a result of quarkgluon interaction inside a hadron, leads to a good agreement of theory with experiment.     

带有两个重夸克的重子谱计算中几个困难问题的研究

由两个重夸克和一个轻夸克组成的重子可以看作是一个两体系统.它的两个重夸克组成一个玻色型的双夸克团.利用B–S方程导出了它的轻夸克和重的双夸克之间的等效相互作用势.在利用这种势计算重子质量的过程中,发现有几个困难问题需要深入探讨.它们是:(1)算符排序,(2)由非相对论展开带来的误差,(3)自旋–自旋耦合,(4)在标量双夸克组成的重子态和矢量双夸克组成的重子态之间的混合.本文详细地讨论并适当地处理了这些问题.     

Finite Volume Effect of Baryons in Strange Hadronic Matter

The finite volume effect of baryons in strange hadronic matter (SHM) is studied within the framework of relativistic mean-field theory. As this effect is concerned, the saturation density of SHM turns lower, and the binding energy per baryon decreases. Its influence to the compression modulus of SHM is also discussed.     

Relativistic effects in the processes of heavy-quark fragmentation to double-heavy baryons

In the framework based on the quasipotential method and relativistic quark model, we investigate the heavy-quark fragmentation into double-heavy baryons with spin J = 1/2, 3/2. Adopting a two-step scenario for the fragmentation, we take into account relativistic corrections to the fragmentation probabilities at both stages of the production process for the double-heavy diquark and double-heavy baryon, correspondingly. We take into account all possible relativistic corrections including the terms connected with the transformation law of the bound-state wave function to the reference frame of the moving bound state. The text was submitted by the author in English.     

Predictions for semileptonic decay rates of charmed baryons in the quark confinement model

Baryons as relativistic three-quark states are investigated in the quark confinement model (QCM), a relativistic quark model based on some assumptions about hadronization and quark confinement. In the framework of the quark-diquark approximation of the three-quark structure of baryons, the main characteristics of light (noncharmed) baryons are calculated. The obtained results agree with experimental data. Predictions are also given for semileptonic decay of charmed baryons and differential production cross-sections in quasielastic neutrino scattering of charmed baryons.     

Baryon formation and dissociation in dense hadronic and quark matter

We study the formation of baryons as composed of quarks and diquarks in hot and dense hadronic matter in a Nambu-Jona-Lasinio (NJL)-type model. We first solve the Dyson-Schwinger equation for the diquark propagator and then use this to solve the Dyson-Schwinger equation for the baryon propagator. We find that stable baryon resonances exist only in the phase of broken chiral symmetry. In the chirally symmetric phase, we do not find a pole in the baryon propagator. In the color-superconducting phase, there is a pole, but it has a large decay width. The diquark does not need to be stable in order to form a stable baryon, a feature typical for so-called Borromean states. Varying the strength of the diquark coupling constant, we also find similarities to the properties of an Efimov state.     

Regge trajectories in the quark model

We prove that the large angular momentum behaviour of the leading Regge trajectory of a meson (q \(\bar q\) ) or a baryon (qqq) can be obtained by minimizing the classical energy of the system for given angular momentum. A two-body quark-antiquark linear potential plus relativistic kinematics produces asymptotically linear Regge trajectories for mesons. For baryons we take either a sum of two-body potentials with half strength or a string of minimum length connecting the quarks, and find in both cases that the favoured configuration is a quark-diquark system and that the baryon and meson trajectories have the same slope. Short-distance singularities of the potential are shown to be unimportant.     

Study of Doubly Heavy Baryon Spectrum via QCD Sum Rules

In this work,we calculate the mass spectrum of doubly heavy baryons with the diquark model in terms of the QCD sum rules.The interpolating currents are composed of a heavy diquark field and a light quark field.Contributions of the operators up to dimension six are taken into account in the operator product expansion.Within a reasonable error tolerance,our numerical results are compatible with other theoretical predictions.This indicates that the diquark picture reflects the reality and is applicable to the study of doubly heavy baryons.     

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.     

Charmed hadron production in \pi p and Kp collisions and leading particle effect by constituent quark-diquark cascade model

We investigate the meson, baryon and anti-baryon productions in and collisions in terms of a constituent cascade model which includes charm flavour. The constituent diquark in an incident baryon has a tendency to get a large momentum fraction, resulting in considerable difference of subenergies for particle productions from quark-diquark and quark-antiquark chains in a meson-baryon collision. As a consequence, the leading particle effects on meson productions are expected to be quite different in and beams at present accelerator energies. Received: 5 November 1996 / Revised version: 30 June 1997 / Published online: 20 February 1998