arXiv subjects
Publications and source records attributed to H. Garcilazo.
We present a study of the baryon spectra for all flavor sectors within a constituent quark model. We address some of the outstanding problems in baryon spectroscopy, as for example the spin splitting evolution for te different flavor sectors, the flavor independence of confinement and the missing state problem.
We review some selected recent results on hadron spectroscopy and related theoretical studies based on constituent quark models.
We calculate the doublet and quartet neutron-deuteron scattering lengths using a nonlocal nucleon-nucleon interaction fully derived from quark-quark interactions. We use as input the $NN$ $^1S_0$ and $^3S_1$-${}^3 D_1$ partial waves. Our result for the quartet scattering length agrees well with the experimental value while the result for the doublet scattering length does not. However, if we take the result for the doublet scattering length together with the one for the triton binding energy they agree well with the so-called Phillips line.
Using the two-body interactions obtained from a chiral constituent quark model we study all $ΛNN$ and $ΣNN$ states with I=0,1,2 and J=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 the $ΛN$ spin-triplet scattering length a_{1/2,1}. Using the hypertriton binding energy we find a narrow interval for the possible values of the $ΛN$ spin-singlet scattering length a_{1/2,0}. We found that the $ΣNN$ system has a quasibound state in the (I,J) = (1,1/2) channel very near threshold with a width of about 2.1 MeV.
We investigate the structure of heavy baryons containing a charm or a bottom quark. We employ a constituent quark model successful in the description of the baryon-baryon interaction which is consistent with the light baryon spectra. We solve exactly the three-quark problem by means of the Faddeev method in momentum space. Heavy baryon spectrum shows a manifest compromise between perturbative and nonperturbative contributions. The flavor dependence of the one-gluon exchange is analyzed. We assign quantum numbers to some already observed resonances and we predict the first radial and orbital excitations of all states with $J=1/2$ or 3/2. We combine our results with heavy quark symmetry and lowest-order SU(3) symmetry breaking to predict the masses and quantum numbers of six still non-measured ground-state beauty baryons.
We calculate the hypertriton binding energy and the $Λd$ and $Σd$ scattering lengths using baryon-baryon interactions obtained from a chiral constituent quark model. We study consistently the $ΛNN$ and $ΣNN$ systems analyzing the effect of the $Σ\leftrightarrow Λ$ conversion. Our interactions correctly predict the hypertriton binding energy. The $(I,J)=(0,3/2)$ $ΛNN$ channel is also attractive and it might have a bound state. From the condition of nonexistence of a (0,3/2) $ΛNN$ bound state, an upper limit for the spin-triplet $ΛN$ scattering length is obtained. We also present results for the elastic and inelastic $ΣN$ and $ΛN$ cross sections. The consistent description of the $ΣN$ scattering cross sections imposes a lower limit for the corresponding spin-triplet scattering lengths. In the $ΣNN$ system the only attractive channels are $(I,J)=(1,1/2)$ and $(0,1/2)$, the $(1,1/2)$ state being the most attractive one.
We revise the role played by symmetry in the study of the low-lying baryon spectrum and comment on the difficulties when trying to generalize the symmetry pattern to higher energy states. We show that for the $(N,Δ)$ part such a generalization is plausible allowing the identification of spectral regularities and the prediction of until now non-identified resonances.
We show that nonstrange baryon resonances can be classified according to multiplets of $SU(4)\otimes O(3)$. We identify spectral regularities and degeneracies that allow us to predict the high spin spectrum from 2 to 3 GeV.
We extract, from a quark model potential that reproduces the number and ordering of nonstrange baryonic resonances up to 2.3 GeV, the quantum numbers for the dominant configurations in the ground and first non-radial excited states. From the pattern of quantum numbers we identify, from data, spectral regularities that allow us to predict the expected high spin low-lying spectrum from 2.3 to 3.0 GeV. $N-Δ$ degeneracies and $N$ parity doublets showing up can be interpreted in terms of a simple dynamics.
We use two-body potentials derived from a constituent quark cluster model to analyze the bound-state problem of the $ΣNN$ system. The observables of the two-body subsystems, $NN$ and $ΣN$, are well reproduced. We do not find $ΣNN$ bound states, but there are two attractive channels with a resonance close above the three-body threshold. These channels are the $(I,J)=(1,1/2)$ and $(0,1/2)$, their quantum numbers, widths and energy ordering consistent with the recently measured strange tribaryons from the $^{4}{\rm He}(K_{\rm stopped}^{-},N)$ reactions in the KEK PS E471 experiment.
We investigate the structure of the SU(3) octet and decuplet baryons employing a constituent quark model designed for the study of the baryon-baryon interaction and successfully applied to the meson spectra. The model considers through the interacting potential perturbative, one-gluon exchange, and non-perturbative, boson exchanges and confinement, aspects of the underlying theory, QCD. We solve the three-quark problem by means of the Faddeev method in momentum space. We analyze the effect of the different terms in the interaction and make contact with the use of relativistic kinematics. We find an explanation to the strong contribution of the pseudoscalar forces in the semirelativistic approach for the octet baryons. A phenomenological recipe for the regularization parameter of the one-gluon exchange is found.
We review the application of non-relativistic constituent quark models to study one, two and three non-strange baryon systems. We present results for the baryon spectra, potentials and observables of the NN, N$Δ$, $ΔΔ$ and NN$^*(1440)$ systems, and also for the binding energies of three non-strange baryon systems. We make emphasis on observable effects related to quark antisymmetry and its interplay with quark dynamics.
Recent lattice QCD calculations suggest a rather abrupt transition in the confinig potential from a linear to a constant behavior. We analyze the effects of such a fast deconfinement in the simplest non-relativistic system, bottomonium.
We study the mass spectrum of baryons with two and three charmed quarks. For double charm baryons the spin splitting is found to be smaller than standard quark-model potential predictions. This splitting is not influenced either by the particular form of the confining potential or by the regularization taken for the contact term of the spin-spin potential. We consistently predict the spectra for triply charmed baryons.
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.
The non-strange baryon spectrum is studied within a three-body model that incorporates relativistic kinematics. We found that the combined effect of relativistic kinematics together with the pion exchange between quarks is able to reverse the order of the first positive- and negative-parity nucleon excited states as observed experimentally. Including the chiral partner of the pion (the $σ$ meson) leads to an overall good description of the spectrum.
We perform a quark model calculation of the $b\bar{b}$ and $c\bar{c}$ spectra from a screened funnel potential form suggested by unquenched lattice calculations. A connection between the lattice screening parameter and an effective gluon mass directly derived from QCD is established. Spin-spin energy splittings, leptonic widths and radiative decays are also examined providing a test for the description of the states.
We study the possible existence of nonstrange dibaryons and tribaryons by solving the bound-state problem of the two- and three-body systems composed of nucleons and deltas. The two-body systems are $NN$, $NΔ$, and $ΔΔ$, while the three-body systems are $NNN$, $NNΔ$, $NΔΔ$, and $ΔΔΔ$. We use as input the nonlocal $NN$, $NΔ$, and $ΔΔ$ potentials derived from the chiral quark cluster model by means of the resonating group method. We compare with previous results obtained from the local version based on the Born-Oppenheimer approximation.