Baryon Regge Trajectories Research Articles

Universal effective hadron dynamics from superconformal algebra

An effective supersymmetric QCD light-front Hamiltonian for hadrons composed of light quarks, which includes a spin-spin interaction between the hadronic constituents, is constructed by embedding superconformal quantum mechanics into AdS space. A specific breaking of conformal symmetry inside the graded algebra determines a unique effective quark-confining potential for light hadrons, as well as remarkable connections between the meson and baryon spectra. The results are consistent with the empirical features of the light-quark hadron spectra, including a universal mass scale for the slopes of the meson and baryon Regge trajectories and a zero-mass pion in the limit of massless quarks. Our analysis is consistently applied to the excitation spectra of the $\pi, \rho, K, K^*$ and $\phi$ meson families as well as to the $N, \Delta, \Lambda, \Sigma, \Sigma^*, \Xi$ and $\Xi^*$ in the baryon sector. We also predict the existence of tetraquarks which are degenerate in mass with baryons with the same angular momentum. The mass of light hadrons is expressed in a universal and frame-independent decomposition in the semiclassical approximation described here.

A rotating string model versus baryon spectra

We continue our program of describing hadrons as rotating strings with massive endpoints. In this paper we propose models of baryons and confront them with the baryon Regge trajectories. We show that these are best fitted by a model of a single string with a quark at one endpoint and a diquark at the other. This model is preferred over the Y-shaped string model with a quark at each endpoint. We show how the model follows from a stringy model of the holographic baryon which includes a baryonic vertex connected with N_c strings to flavor probe branes. From fitting to baryonic data we find that there is no clear evidence for a non-zero baryonic vertex mass, but if there is such a mass it should be located at one of the string endpoints. The available baryon trajectories in the angular momentum plane (J,M^2), involving light, strange, and charmed baryons, are rather well fitted when adding masses to the string endpoints, with a single universal slope of 0.95 GeV^-2. Most of the results for the quark masses are then found to be consistent with the results extracted from the meson spectra in a preceding paper, where the value of the slope emerging from the meson fits was found to be 0.90 GeV^-2. In the plane of quantum radial excitations, (n,M^2), we also find a good agreement between the meson and baryon slopes. The flavor structure of the diquark is examined, where our interest lies in particular on baryons composed of more than one quark heavier than the u and d quarks. For these baryons we present a method of checking the holographic interpretation of our results.

Spectroscopy and Regge trajectories of heavy baryons in the relativistic quark-diquark picture

Mass spectra of heavy baryons are calculated in the heavy-quark--light-diquark picture in the framework of the QCD-motivated relativistic quark model. The dynamics of light quarks in the diquark as well as the dynamics of the heavy quark and light diquark in the baryon are treated completely relativistically without application of nonrelativistic v/c and heavy quark 1/m_Q expansions. Such approach allows us to get predictions for the heavy baryon masses for rather high orbital and radial excitations. On this basis the Regge trajectories of heavy baryons for orbital and radial excitations are constructed, and their linearity, parallelism, and equidistance are verified. The relations between the slopes and intercepts of heavy baryons are considered and a comparison of the slopes of Regge trajectories for heavy baryons and heavy-light mesons is performed. All available experimental data on heavy baryons fit nicely to the constructed Regge trajectories. The possible assignment of the quantum numbers to the observed excited charmed baryons is discussed.

Holographic approach to Regge trajectory and rotating D5 brane

We study the Regge trajectories of holographic mesons and baryons by considering rotating strings and D5 brane, which is introduced as the baryon vertex. Our model is based on the type IIB superstring theory with the background of asymptotic $AdS_5\times S^5$. This background is dual to a confining supersymmetric Yang-Mills theory (SYM) with gauge condensate, $<F^2>$, which determines the tension of the linear potential between the quark and anti-quark. Then the slope of the meson trajectory ($\alpha'_{M}$) is given by this condensate as $\alpha'_{M}=1/\sqrt{\pi <F^2>}$ at large spin $J$. This relation is compatible with the other theoretical results and experiments. For the baryon, we show the importance of spinning baryon vertex to obtain a Regge slope compatible with the one of $N$ and $\Delta$ series. In both cases, mesons and baryons, the trajectories are shifted to large mass side with the same slope for increasing current quark mass.

Hadronic Regge trajectories: Problems and approaches

We scrutinized hadronic Regge trajectories in a framework of two different models --- string and potential. Our results are compared with broad spectrum of existing theoretical quark models and all experimental data from PDG98. It was recognized that Regge trajectories for mesons and baryons are not straight and parallel lines in general in the current resonance region both experimentally and theoretically, but very often have appreciable curvature, which is flavor-dependent. For a set of baryon Regge trajectories this fact is well described in the considered potential model. The standard string models predict linear trajectories at high angular momenta J with some form of nonlinearity at low J.

Deuteron photodisintegration within the Quark-Gluon Strings Model and QCD motivated nonlinear Regge trajectories

We investigate deuteron two-body photodisintegration within the framework of the Quark-Gluon Strings Model with nonlinear baryon Regge trajectories. Special attention is paid to the use of QCD motivated Regge trajectories of the logarithmic and square-root form which have been suggested recently by Brisudov\'{a}, Burakovsky and Goldman. We find that the recent experimental data from TJNAF in the few GeV region can reasonably be described by the model. Angular distributions at different $\gamma$-energies are presented and the effect of a forward-backward asymmetry is discussed. Predictions for the energy dependence of $d\sigma/dt$ at higher energies and different $\Theta_{cm}$ are presented, too.

New quadratic baryon mass relations

By assuming the existence of (quasi)linear baryon Regge trajectories, we derive new quadratic Gell-Mann--Okubo-type baryon mass relations. These relations are used to predict the masses of the charmed baryons absent from the baryon summary table so far, in good agreement with the predictions of many other approaches.

Relativistic three-dimensional two- and three-body equations on a null plane and applications to meson and baryon Regge trajectories

We start from a field-theoretical model of zero range approximation to derive three-dimensional relativistic two- and three-body equations on a null plane. We generalize those equations to finite range interactions. We propose a three-body null-plane equation whose form is different from the one presented earlier in the framework of light-cone dynamics. We discuss the choices of the kernels in two- and three-body cases and apply our model to the description of meson and baryon Regge trajectories. Our approach overcomes some theoretical and phenomenological difficulties met in preceding relativized treatments of the three-body problem.

A Rotating Bag Model for Hadrons. II: Regge Trajectories of Baryons

The MIT bag model is modified in order to describe rotational motion of hadrons. It has a kind of «diatomic molecular» structure. The rotational excitation of the MIT bag is described by the polarized two colored sub-bags which are connected with each other by the gluon flux. One sub-bag contains a quark and the other has an antiquark for mesons. For baryons, the latter sub-bag contains the remaining two quarks instead of the antiquark. The Regge trajectories of hadrons are explained qualitatively by our new model with the usual MIT bag parameters. In particular the Regge slopes are reproduced fairly well. It is also pointed out that the gluon flux plays an important role in the rotational motion of hadrons

EFFECTIVE HAMILTONIAN OF THE RELATIVISTIC QUARK MODEL

We derive an effective Hamiltonian of the relativistic quark model. In the limit of zero quark masses, we obtain linear Regge trajectories for mesons. Based on the diquark-antiquark symmetry, we show that the Regge trajectories of baryons and mesons are parallel at high angular moments. We discuss the breaking of the hadronic supersymmetry and obtain a mass relation of mesons and baryons.

Relativistic calculation of baryon properties in nonperturbative QCD

Baryon structure and baryon Regge trajectories are studied in a relativistic approach based on the method of vacuum correlators. Generation of constituent mass for quarks and diquarks is studied quantitatively for baryons with angular momenta up to L=5. Two types of linear baryon Regge trajectorieis are found with the same asymptotic slope equal to the mesonic slope.

Regge trajectories of baryons in the MIT bag model

We investigate Regge trajectories of baryons in the MIT bag model. It is shown that the energy spectra shown by the trajectories can be described fairly well by the stringlike solutions of the bag model. In particular, three strings with one junction and three ends can explain the delta trajectory better than one string with two ends. The three ends occupied by each quark are assumed to be an equilateral triangle configuration in our calculations.

Baryon Regge trajectories from the area law of the Wilson loop

Abstract In the proper-time path integral representation of the three-quark Green function, baryon masses are calculated for large angular momenta L . The dynamics is given by vacuum background fields in the Wilson loop. Assuming an area law for large Wilson loops one obtains linear baryon Regge trajectories with the same slope as for mesons. For large L the baryon has an asymmetric structure of the quark-diquark type. Dynamic masses of the quark and diquark are generated, which grow with L .

The baryon mass spectrum and the reciprocity principle of Born

The reciprocity principle of Born, when used in the context of the phase-space representation of relativistic quantum mechanics, suggests a Yukawa-like equation whose eigenfunctions properly describe the baryon mass spectrum. Good numerical agreement with experimental data is established by introducing internal SU3 symmetry, which when broken leads to a satisfactory quantitative description of the well-known linear baryon Regge trajectories.

Semiclassical approach to the quark-string model and the hadron spectrum. II. Baryons and exotic hadrons

Leading Regge trajectories of baryons and exotic hadrons are studied in the quark-string model. Boundary conditions at the string end point and the junction provide a simple topological rule on the configuration of hadron structure and also provide a relationship between the asymptotic Regge slope and the hadron structure. The center of mass of the string is shown to play a special role in classical solutions. The quark-diquark type of the baryon is absent in our formalism.

Perturbative recipe for quark-gluon theories and some of its applications

We explore the possibility that the intercepts of the nonstrange meson and baryon Regge trajectories are simply related to quark spin. This possibility arises if one adopts a multiperipheral bootstrap for these (ordinary) trajectories and also a perturbative recipe relating a process with a given number of particles to quark-gluon diagrams. The possible implication of the scheme for the Pomeron are also discussed.

Chew-Frautschi plot and string structure of baryons

In this let ter we show tha t the baryon Chew-Frautschi plots exhibit some regular i ty suggested by the string structure of baryons. I t has been argued (1,2) tha t for the string structure of baryons there are theoret ical ly three possible string configurations which connect the three quarks as shown in fig. 1. The regular i ty we are concerned with is just the one due to the th i rd configuration (fig. lc)). At present, the string with quarks a t tached at the end points has not yet been successfully formulated. The spin and the un i ta ry spin of the quark are, however, impor tan t in discussing the structure of baryons. So tha t we take into account these spins, but we ignore the mass of the quark. In what follows, the whole orbital angular momentum J5 is assumed due to the string motion. A~TRU has recently invest igated (~) the classical motion of the relativistic string with the junction (fig. le)). He found a s ta t ionary solution where all three branches of the revolving string have the same length (the symmetric configuration). There might exist other excitat ion modes: only one or two branches can have large length and the remainders are infinitesimal (no excitation). In the la t te r modes, the baryonic string behaves like a mesonic string because the infinitesimal branches may give no marked contributions to the energy and to the angular momentum. These modes will produce the leading baryon Regge trajectories with almost the same slope as tha t of meson trajectories, i.e. ~'___ 1 (GeV) -2. On the other hand, the slope of the t ra jec tory corresponding to the symmetr ic configuration is predicted to be equal to ~ t imes the slope of the leading t ra jec tory mentioned above (2). In the meson theory, the well-known classical solution (the rotat ing single r igid string) gives the maximum angular momentum for a given energy and corresponds to the upper boundary of the continuum of more general classical solutions. This fact gives the unique connection between the t ra jec tory of this classical solution and the quantummechanical (leading) Reggc trajectory. For our classical solutions the symmetric configuration gives lower angular momenta than those of the mesonlike configuration. However, these two classical motions cannot be superposed on each other, since these have the junction at quite different positions and may belong to different branches

Total Decay Widths of Resonances and Regge Trajectories

The compatibility of the imaginary parts of baryon Regge trajectories alpha (u) with the almost linearly rising feature of Re alpha (u) is investigated. Corrections to Re alpha (u) due to nonvanishing Im alpha (u), which is estimated from the total decay widths of resonances lying on the leading trajectories, are calculated in a phenomenological way through dispersion relations with unitarity cuts only. It is found that Im alpha (u) must decrease when u becomes large in order to maintain the deviation of Re alpha (u) from linearity small in the low energy region. A brief discussion on meson trajectories is also presented. (auth)

Self-sustaining regime for Regge trajectories

Abstract The question of correspondence between the experimental data on baryon Regge trajectories and the spectral representation without an additional linear term is considered. The hypothesis of ‘self-sustaining regime’ for trajectories is formulated and its consequences are discussed. The determining role of inelastic contributions to Im α is established. We propose the hypothesis of the cascade mechanism of forming of the total resonances widths.

EXCHANGE DEGENERACY AND SU(3) FOR BARYONS

It is assumed that the contributions of baryon Regge trajectories cancel in the imaginary parts of meson-baryon scattering amplitudes in states of the SU(3) representations 10* and 27. Predictions concerning interaction ratios, mass splitting, and particle mixing are made and compared with experiment.