Search

Shoichi Sakata and his Nagoya School made a lot of important achievements at the predawn of the particle physics revolution. The “two-meson” theory (introduction of the second generation leptons), the “C-meson theory” (a theory which inspired Tomonaga’s renormalization theory), the “Sakata model” (a precursor to the quark model), and the “MakiNakagawa-Sakata” theory on the neutrino mixings are among them. These outputs are now regarded as essential ingredients in modern particle physics. Sakata also took his leadership in setting up democratic administration system in his theoretical particle physics group (Eken). It was this democratic atmosphere in which many excellent physicists were brought up as Sakata’s diciples. In this talk, I introduce Sakata and his achievements in physics, showing various materials archived in the Sakata Memorial Archival Library (SMAL), an archival repository of primary material showing Sakata’s activities. These SMAL documents vividly show Sakata’s way of thinking in his approach to the new physics.

A phase structure and phase transitions are investigated in the modified Bonn quark model. The force strength, which represents the particle-hole type interaction, is devised so as to depend on the quark number, namely quark number density. As a result, it is shown that the phase transition from the quark-triplet state as a nucleon to the quark-pair state as a color-superconducting state occurs as the density increases.

Ground-state energies are investigated in a many-quark model with pairing interactions, which has the su(4)-algebraic structure. Exact eigenstates in the boson realization method are constructed by imposing a color-singlet condition developed in the previous paper. An interaction term breaking the su(4)-dynamical symmetry plays an important role to determine the ground state. As a result, a quark-pairing state or a quark-triplet state as a nucleon is realized with a certain value of a variable which is regarded as an order parameter. In addition to the parameter regions in which these ground states are realized, it is shown that there are two transition regions between the quark-pairing and the quark-triplet states with different values of the order parameter.

The low-energy breakup differential cross sections of the neutron-deuteron (nd) scattering are studied by employing the energy-independent version of the quark-model baryon-baryon interaction fss2. This interaction reproduces almost all the breakup differential cross sections predicted by the meson-exchange potentials for the neutron incident energies $E_n \leq$ 65 MeV. The space star anomaly of 13 MeV nd scattering is not improved even in our model. Some overestimation of the breakup differential cross sections at $E_n$=22.7 - 65 MeV implies that systematic studies of various breakup configurations are necessary both experimentally and theoretically., 32 pages, 12 figures, submitted to Prog. Theor. Phys

We report the chiral quark model approach for the study of baryon resonances in meson photoproduction and meson-nucleon scattering processes. Focussing on the $\pi N$ and $K N$ scatterings, we show that the cross sections near threshold can be well accounted for by the chiral quark model with only few parameters. The $S$-wave dominance in both $\pi^- p\to \eta n$ and $K^- p\to \Sigma^0\pi^0$ can be well understood in the quark model framework. In particular, the quark model provides a constraint on the relative signs for resonance coupling form factors, which seems to be consistent with results from isobaric models., Comment: Talk given on the New Frontiers in QCD 2010, YITP, Japan

Based on the boson realization, the ground state and phase structure are investigated in a many-quark model with algebraic structure developed in our previous paper, in which the two-body pairing and particle-hole type interactions are active. The physical interpretation of the exact eigenstates obtained in the boson realization in our previous paper is given in a many-quark model with su(4) algebraic structure., 15 pages, 4 figures, using PTPTeX.cls

With the use of a certain type of the Schwinger boson representation of the su(4) algebra, the Bonn model for many-quark systems and an extension of the model, in which the energies of the various exact states are controled, namely, the energies are enhanced or de-enhanced, are investigated. In the boson space spanned by the use of the boson realization, the exact eigenstates and the exact energy eigenvalues are constructed. Thus, all the results in this Bonn model and its extension are analytically expressed in the exact forms. Especially, the quark-triplet formation and the pairing correlation in many-quark states are widely discussed in the boson realization.

In this talk, I briefly review how Nagoya physics has contributed to the development of flavor physics over the past 50 years. It began with the introduction of Sakata model back in 1956, and recently it contributed to the discovery of CP violation in 2000. Along the way Kobayashi and Maskawa completed the standard model by introducing the KM ansatz for CP violation. We shall also describe two discoveries by Nagoya emulsion group made before 1990: (1) the first evidence for the charm quark; (2) discovery of the D 0 and D + mesons. §1. Introduction — Sakata’s physics There have been many major Japanese contributors to elementary particle physics. In this talk I was asked by the organizers to talk about Nagoya’s contributions to particle physics. I am not a historian and I will not try to be one. There are many people who have more balanced and complete knowledge of Nagoya physics. So, I will concentrate on what I know best and leave the rest to other experts. With an apology in advance, I shall concentrate on Nagoya’s contributions to part of flavor physics which I was involved in. When I was a graduate student at Princeton during the mid to late 1960’s, most of the people around me have been studying analyticity, unitarity, and dispersion relations. We have been told by our leaders that field theory cannot deal with strong interaction dynamics. The nuclear democracy, which states that all particles were bound states of each other, was thought to be correct, and idea that fundamental constituents existed and that their interactions are governed by field theory was not very popular — if not rejected. Fortunately, Nagoya was located very far from these centers and it was out of their reach. The Sakata model was introduced in this type of atmosphere. It was little bit ahead of its time — the fundamental particles in this model was P , N ,a ndΛ. We now know about the fractionally charged quarks, and Sakata’s model was wrong. But, it certainly paved the way for the correct model, Gell-Mann’s 1) SU(3) of quarks in 1964. It is interesting to observe that Gell-Mann 2) too was influenced by the propaganda of the establishment. He had to justify introducing such fundamental particles — stating that they are only a mathematical tool and they can be thrown out after physics has been extracted from the quark model.

We study the five-quark system $uudd{\bar s}$ in the standard non-relativistic quark model by solving the scattering problem. Using the Gaussian Expansion Method (GEM), we perform the almost precise multi-quark calculations by treating a very large five-body modelspace including the NK scattering channel explicitly. Although a lot of pseudostates (discretized continuum states) with $J^\pi={1/2}^\pm$ and $J^\pi={3/2}^\pm$ are obtained within the bound-state approximation, all the states in $1.4-1.85$ GeV in mass around ${\rm {\rm \Theta}}^+(1540)$ melt into non-resonant continuum states through the coupling with the NK scattering state in the realistic case, i.e., there is no five-quark resonance below 1.85GeV. Instead, we predict a five-quark resonance state of $J^\pi={1/2}^-$ with the mass of about 1.9GeV and the width of $\Gamma \simeq$ 2.68MeV. Similar calculation is done for the four-quark system $c{\bar c}q{\bar q}$ ($q=u,d$) in connection with X$^0$(3872).

We investigate the in-medium modification of pseudoscalar and vector mesons within a QCD motivated chiral quark model by solving the Dyson-Schwinger equations for quarks and mesons at finite temperature in the wide mass range from light mesons (π, σρ ) to opencharm mesons (D, D ∗ ). At the chiral/deconfinement phase transition, the quark-antiquark bound states enter the continuum of unbound states and become broad resonances (Mott effect). We calculate the in-medium cross section for charmonium breakup processes due to light hadron impact within a chiral Lagrangian approach and show that the Mott effect for the D-mesons effectively reduces the threshold for charmonium breakup and leads to a step-like behaviour of the reaction rate. This is suggested as an explanation of the anomalous J/ψ suppression phenomenon in the NA50 experiment.

The study of the weak radiative decay B → K∗γ has attracted considerable attention as a test of the Standard Model (SM) since the CLEO experiment 1) gave the preliminary value of the branching ratio Br(B → K∗γ) = (4.0±1.7±0.8)×10−5. This decay mode arises from the quark level process b → sγ via flavor changing neutral current (FCNC). There are two essential contributions to the amplitude of the weak radiative decay b → sγ, the short distance (SD) contribution due to the electromagnetic penguin and the long distance (LD) contribution due to strong interactions. The LD contribution is calculated using the vector meson dominance (VMD) method 2) at the quark level as b → s[cc], followed by the conversion [cc] → γ. In order to obtain the relevant ratio Br(B → K∗γ), it is necessary to take into account the quark confined effect. The estimation of this effect is a problem of non-perturbative QCD, and we must use some models presently. In a previous work 3) we studied the problem of determining the width of this decay by using the covariant oscillator quark model (COQM), 4) where we have taken into account only the leading SD contribution. In the present work we improve our calculation by adding the LD contribution.

The standard theory of elementary particles has achieved remarkable success in describing weak-electromagnetic properties and reactions of leptons. It is successful for hadrons although a care must be taken for corrections due to strong interaction. At high energy perturbative calculations are reliable thanks to the asymptotic free nature of the strong interaction, while low energy phenomena can be studied with the help of low energy effective theories based on the low energy symmetries, such as gauge invariance and chiral symmetry. Also the renormalizability guaranteed by the gauge invariance allows us to relate phenomena at different energy-momentum scale with each other. For instance, employing the renormalization group equation we study energy-scale dependence of physical matrix elements. Yet, a few unsolved problems remain for the hadronic weak interactions. One such problem is the mechanism for nonleptonic weak interactions of hadrons. For instance, the ∆I =1 /2 dominance in the flavor changing weak decays has not convincingly been explained. Chiral perturbation theory for the weak decays of hyperons cannot even fit experimental data of the decay amplitudes. One of the reasons of the difficulty seems that nonperturbative corrections of the strong interaction are fully intermingled with the weak interaction. There is no current conservation which protects the weak vertex from strong renormalization contrary to leptonic processes, where the vector and the axial vector currents are (almost) conserved. This has been a challenging problem in the hadron physics. Recent experimental studies of weak decays of hypernuclei have added a new difficulty to the nonleptonic weak interaction of hadrons. In hypernuclei, the Λ decays from the ground state into nonstrange hadrons. The standard decay modes of Λ are Λ → pπ − and Λ → nπ 0 , but these modes are known to be suppressed in nuclear medium as the momentum of the final nucleon is not large enough to go above the Fermi surface. Instead, the main decay modes of medium-to heavy

The role of pseudoscalar mesons in the dynamical properties of baryon resonances is examinedby means of the constituent quark mod el with meson-quark coupling. Since resonance properties are closely relatedto meson-baryon scatterings, it is important to includ e reaction processes as well as mass spectra in the analysis. The isobar model is employed to properly extract information of baryon resonances from reaction amplitudes. Prominent features of resonance spectra are reproduced fairly well by taking account of baryon selfenergies due to meson-quark coupling. Several problems remained in the static quark model of baryons, e.g. Λ(1405)-Λ(1520) mass difference, are also studied. Brief comments on some improvements of the present model are given.

Motivated by the observation of the decay B to K* gamma by the CLEO collaboration, we have systematically analyzed the weak radiative decay Lambda_b to Lambda gamma, evaluating the confined effects of quarks in the covariant oscillator quark model. This decay process receives both short distance (electromagnetic penguins at the one loop level) the long distance contributions in the quark level. The long distance contributions are analyzed using the vector meson dominance (VMD) method. The estimated branching ratio is found to be 0.23 times 10^-5.

The spectra of exclusive semi-leptonic decays of heavy b-quark and c-quark mesons are derived, taking account of confined effects of quarks in the covariant oscillator quark model (COQM). The respective partial widths are also calculated using the standard values of KM-matrix elements. In COQM all kinematics and effective interactions are expressed in a manifestly covariant and unified way. The effective weak currents are given as overlapping integrals between initial and final hadron “wave functions” and lead to the many relations among the form factors, including those derived by HQET in the case of heavy-light quark meson systems. On the other hand, for reference the values of the relevant KM-matrix elements, estimated in COQM directly from each experimental decay width, are also given.

We study all the SU(3) baryonic states known experimentally and identify them in the scheme of the deformed oscillator quark (DOQ) model. The DOQ model is motivated by confinement of quarks and chiral symmetry breaking, which are the most important nonperturbative phenomena of QCD. We find most of the baryonic states fall into the DOQ scheme. We then attempt to study the microscopic origin of the DOQ model using a model of three constituent quarks with two-body interactions. We find, however, that such a simple treatment is not able to produce the large deformation effect. We argue then that the confinement caused by the gluon dynamics is essentially important for the deformed baryons.

Exclusive weak radiative B meson decays are studied using the covariant oscillator quark model. The branching ratios for the processes B0 to K*0 gamma and B to K* gamma have been estimated. These are in reasonable agreement with the available experimental data. The calculation has been extended to the CKM-suppressed decay processes B- to rho- gamma and Bs to K*0 gamma ., Comment: 9 pages, uses ptptex.sty

We present a model to describe inclusive meson production in e+ e- reactions based on a quark cascade approach whose formulation is put in terms of diffusion equations for three quark flavors (u, d, s). These equations are solved by using a formalism previously developed for the problem of the electromagnetic cascade generated in the atmosphere by cosmic­ ray interactions. The obtained solutions are given in terms of a combination of power-law functions whose profiles are adequate to describe the characteristics observed in the inclusive spectrum of mesons. Quantum Chromodynamics (QCD), the putative theory of fundamental hadronic interactions, has not yet provided a rigorous scheme to describe how hadrons are produced in electron-positron annihilation processes. The status of art in this matter is represented by QCD-based models which are usually implemented in terms of very complex Monte Carlo algorithms. Such models/algorithms have become able to describe more and more data, but at expenses of increasing complexity. Probably, that is the best that can be done about this subject and trying to simplify the problem would correspond to distort it. However, simpler analytical models can be helpful in the sense that they (hope­ fully) may provide a more intuitive view about the role of the elementary interactions underlying such processes (for a general account on Monte Carlo and analytical mod­ els see an excellent review in Ref. 1)). The present paper is an attempt to develop one of these models. Its basic idea is not new: it consists fundamentally in expressing the cascade of quarks formed after the collision in terms of diffusion equations. Due to the nature of the problem and to the dynamics of the quark/ gluon interactions, these equations are necessarily coupled which renders this problem very complex in mathematical terms. Even so, in the present approach we show that it is possible to obtain simple solutions for the case of three flavors by applying a method of calculation previously developed to the problem of the electromagnetic cascade generated in the atmosphere

oscillator quark model. Our results on gluonia especially seem to be consistent with the recent lattice-QeD results, and also to suggest that the pomeron is a leading gluonium trajectory, in comparison with phenomenological properties of the pomeron trajectory.

Scattering observables of the N N interaction are investigated in a recent quark model developed for a unified description of N N and hyperon-nucleon systems. Satisfactory agree­ ment with experiment is obtained for the total and differential cross sections, as well as the polarization observables of np and pp scattering. Since quantum chromodynamics (QCD) is widely accepted as the dynamics un­ derlying the strong interaction, 1) there have been many attempts to investigate the baryon-baryon interaction in terms of QCD-inspired quark models. The study of the nucleon-nucleon (N N) interaction is particularly important, not only because the N N system is most fundamental, but also because all the essential aspects and ingredients of this kind of approach are already involved in this system. The most successful quark-model study of the N N interaction is carried out within the frame­ work of the resonating-group method (RGM) applied to the (3q)-(3q) system, in which the gluon effect is incorporated through the color analog of the Fermi-Breit (FB) interaction in the one-gluon exchange approximation, and through a simple power-law confinement potential put in by hand. 2) The conclusion drawn from such calculations can be summarized as follows: The phase-shift equivalent local poten­ tials derived from the (3q)-(3q) model of N N scattering are short-ranged, strongly energy dependent and purely repulsive. The repulsive core of several hundred MeV is determined mainly by the color-magnetic term of the FB interaction (for even-parity states) and by the effect of the Pauli principle (for odd-parity states). Although the confinement potential strongly influences single-baryon properties (such as the ab­ solute values of baryon masses), it plays an insignificant role in the N N scattering. The most important conclusion of the simple (3q)-(3q) RGM is that it gives only the extreme short-range part of the N N interaction and fails to make a natural connec­ tion to the mesonic degree of freedom responsible for the medium- and long-range attractive part of this interaction. In recent quark-model studies for the N N inter­ action, various kinds of effective meson-exchange potentials (EMEP) are therefore introduced more or less phenomenologically, to achieve a realistic description of the experimental data. Recent interest in the hyperon-nucleon (Y N) interaction has motivated the reex­ amination of the EMEP employed in the quark model for the N N interaction. In our

A prominent feature of the first order rotational correction (or the 1/Nc correction) to YA recently found within the framework of the chiral quark soliton model (CQSM) is that the corresponding effect is entirely missing in the Skyrme model. We attempt to reveal the origin of this crucial observation through a comparison of two approaches based on the lagrangian of the chiral quark model. In the first approach, which is nothing but a path integral formulation of the CQSM, it is shown that a crucial ingredient leading to this novel 1/Nc correction is the correct account of the physical time order of two collective space operators in the quantization of the rotational zero-energy mode. On the other hand, the standard functional bosonization of the same lagrangian turns out to lose this indispensable information on the chronological order of these two operators. Once this information is lost, the generalized time-reversal invariance or the particle conjugation symmetry does not allow this 1/Nc correction to survive, which explains the reason why the gA problem of the Skyrme model arises. On the other hand, within the CQSM the existence of the 1/Nc correction to YA is shown to be nothing incompatible with the particle conjugation symmetry of strong interactions. It is emphas­ ized that the same 1/Nc correction to YA is also obtained by using an ordinary perturbation theory based on the cranking procedure, contrary to a recent claim. We also discuss the recently raised PCAC consistency problem to show that the required 1/Nc correction term in the equation of motion naturally follows from an action principle so that there is no contradiction between the new 1/Nc correction to YA and the PCAC relation.

A detailed quark-model study of the AN-IN(/=1/2) system is given in a coupled-channel formulation of the RGM-F which has been recently introduced to achieve a unified understanding of the NN and hyperon-nucleon interaction. It is found that the effect of the AN-IN transition potential is strongly enhanced in the threshold region through important contributions of the non­ central components. The antisymmetric LSH force, which is characteristically strong in the quark model with the full Fermi-Breit interaction, reproduces the prominent bump structure in the AN total scattering cross sections at energies slightly below the IN threshold.

A unified description of the hyperon-nucleon interaction consistent with the NN interaction is given in the RGM formulation of the SUs quark model, in which the full Fermi-Breit interaction with explicit flavor symmetry breaking is incorporated. The medium-range central and long-range tensor components of the hyperon-nucleon interaction are augumented by the effective meson-exchange potentials generated from the scalar-meson nonet and ;r and K mesons of the Nijmegen model-F. With two parameters determined from the deuteron binding energy and NN 'So phase shift, all the low-energy cross sections of the hyperon-nucleon interaction currently available are reasonably reproduced. The analysis of NN and ;I;+p systems is presented.

The years of 1960-1965 were a remarkable period for Yoichiro Nambu. Starting with a reformulation of BCS theory with emphasis on gauge invariance, he recognized the realization of spontaneous chiral symmetry breaking in particle physics as is evidenced by the Goldberger-Treiman relation. A concrete model of Nambu and Jona-Lasinio illustrated the essence of the Nambu-Goldstone theorem and the idea of soft pions. After the proposal of the quark model by Gell-Mann, he together with Han constructed an alternative model of integrally charged quarks with possible non-Abelian gluons. All those remarkable works were performed during the years 1960-1965. Here I briefly review those works following the original papers of Nambu chronologically, together with a brief introduction to a formulation of Neother's theorem and Ward-Takahashi identities using path integrals. This article is mostly based on a lecture given at the Nambu Memorial Symposium held at Osaka City University in September 2015, where Nambu started his professional career., Comment: 21 pages. An introductory lecture given at Nambu Memorial Symposium at Osaka City University, September 29, 2015

The recently discovered first order rotational correction to the nucleon axial-vector coupling constant gA within the chiral quark soliton model appears to provide us with an unexpectedly simple solution to the long-standing gA problem in the Skyrme model. A prominent feature of this special type of 1/Nc correction is that the corresponding effect is entirely missing in the Skyrme model. We try to clarify the underlying mathematical reason why such a crucial difference appears between the two effective theories of baryons.

We study the lambda hypernuclei and neutron stars in terms of the relativistic mean field theory. A special emphasis is placed on the importance of the lambda -omega tensor coupling, which affects largely the spin-orbit splitting. The presently available data on hypernuclei are not good enough to identify its strength. We find that the neutron star property is sensitive to its strength and the observational neutron star mass provides the necessity of the tensor coupling. For a long time, special attention has been paid to the lambda hypernuclei which are nuclei with a lambda particle with strangeness quantum number. We expect to extract a lot of detailed knowledge concerning strangeness from the investigation of lambda hypernuclei. In fact, spectroscopic studies of the lambda hypernuclei show conspicuous features, that is, as compared with the nucleon, a lambda is weakly bound in nuclear medium and its spin-orbit splitting is quite smali_lHl The microscopic understanding of these properties was principally given in two different viewpoints. One is based on the meson exchange model and the other the quark modeL In terms of the meson exchange picture, Brockmann and Weise were the first to derive the A-N interaction. 5 l By taking the 2Jr and 3Jr exchanges and their correla­ tions into account, they performed a detailed analysis for the dominant part of the A-N interaction which is constructed from the isoscalar-scalar and -vector channels. The resultant scalar and the vector parts become smaller with a common reduction factor of about three than the corresponding ones for the N-N interaction. Namely representing the SCalar and the Vector partS aS V(S) and V(V) respectively

In this paper, we introduce two parts of work: the hyperon-meson vertex structure from the one-gluon-exchange quark-antiquark pair creation model and the hyperon-nucleon interactions on a modified quark potential model. For both parts some significant results have been obtained.

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

We get the electric charge distribution of the lambda particle in 5U(3) Skyrme model using the "collective approach". We compare it with the electric charge distribution obtained in the non­ relativistic quark model. It is pointed out that the electric charge distribution of the lambda from the collective approach has. an opposite sign to those obtained from the non-relativistic quark model and the bound state approach in the 5U(3) Skyrme model.

In the covariant oscillator quark model (COQM) the squared-mass spectra of confined meson systems are described by harmonic oscillators. On the basis of a «proto-type» classical Lagrangian for the confined particle system, which leads to the basic equation in the COQM, we propose, in this work, a hypothesis of universal spring, which predicts the respective values of oscillator quanta in terms of constituent quark masses and a spring constant. This prediction is compared systematically with experiments by examining various kinds of meson-mass trajectories versus number of oscillator quanta in all possible cases of flavor-configurations. It seems to us that our universality is realized experimentally, although much more confirmation is necessary

Recently, the European Muon Collaboration (EMC) measured the polarized structure function of the proton g/(x, Q2).1) The EMC found that the value of the first moment of g/(x, Q2) is smaller than the one expected by the naive quark modeL) The result has been investigated by means of various approaches. However, the sign. and magnitude of the sea and gluon polarizations are not clear. For example, Kobayakawa et aL) suggest the positive sea and positive gluon polarizations, while Cheng et aL) do the negative sea and negative gluon polarizations. Also, many authors),6) have discussed the negative sea and positive gluon polarizations. It is important to clarify the relations among their results. In this paper, we investigate the sea and gluon polarizations in the proton by considering the effect of the anomaly7) and the broken flavour-SU(3) (SUA3)) sea. It is pointed out that the sign and magnitude of the sea and gluon contributions demanded by the experimental data, are strongly correlated to the amount of the spins carried by valence quarks and the SUA3) symmetry breaking parametenwhen combined with the data of neutron and hyperon beta decays.S),9) Also, we calculate the magnitude of the valence quark spins in a framework of a constituent quark model,6) as an example. We consider the polarized parton distributions in a proton with positive helicity. Let us introduce the helicity-weighted quark and gluon densities Llq(x, Q2), Llg(x, Q2) and their polarizations (first moments) Llq( Q2), Llg( Q2) at Q2 Ge V

Various types of meson condensations are discussed within the chiral symmetry approach. For P-wave pion condensations, some realistic effects such as inclusion of the isobar .d(l232), baryon-baryon short range correlations, and form factors are taken into account in a simple way; inclusion of isobar is described in terms of SU(4) constituent quark model and short range correlations are simulated by the minimal interactions with the Landau-Migdal parameter. Kaon condensation by virtue of s-wave condensation is also described in a similar framework.

Characteristic features of the baryon-meson coupling vertices are studied in terms of a quark model in which quark-antiquark pair-creation processes inherent in the quark-gluon interaction Lagrangian are explicitly incorporated. It is shown that the standard non-relativistic baryon-meson vertex functions are naturally derived from quark exchange diagrams in a way that approximate SU 6 relations are apparently satisfied for the coupling constants. Under the assumption of the flavor SU 3 symmetry, this formalism yields a simple analytic expression for the coupling constants of S'-wave baryons, which contains only- one parameter related to the overall strength. The model predictions are examined in conjunction with the available empirical information. The effect of flavor symmetry breaking is also discussed with respect to the pion decay widths of decuplet baryons

An attempt to understand better the modern situation with short range baryon-baryon (by example of nucleon-nucleon) interaction is undertaken. The article covers five main ingredients of the whole problem: (i) visual demonstration of the inadequacy of modern models for short-range N-N interaction, (ii) the general property of the Wigner supermultiplet symmetry of interaction potentials for composite particles, (iii) a short outline of the main results of realistic six-quark microscopic calculations for nucleon-nucleon interaction and the results based on the Moscow model for N-N interaction

The masses of s-wave bottom baryons are discussed in a semirelativistic quark model, on the basis of a quark-distance relation. We stress that the Σ b is heavier than Ξ' b (b[su], b[sd]) containing the antisymmetric su(or sd) subsystem. We conclude that the two candidates for Λ b with very different masses are different states; Basile et al.'s result 5425 +175 −75 MeV is Λ b (b([du]), but Arenton et al.'s result ∼5750 MeV is Ξ' 0 b (b[su])

We study the chiral invariant quark model lagrangians under the Hartree approximation for construction of a hedgehog solution with the baryon number B=1. We take into account the Dirac sea contributions to the energy and various densities in terms of the heat-kernel method. With the parameters of the Nambu-Jona-Lasinio model lagrangian fixed by the meson properties, we do not find any B=1 hedgehog solutions except for one case, even which is, however, unstable against small perturbation. We study then the Diakonov-Petrov model lagrangian, which is introduced by investigating the properties of the quark field in the instanton background in QCD

The chiral quark model as an effective theory of low energy QCD contains an abundance of physics despite its extremely simple appearance. The soliton model of baryons based on this effective lagrangian is reviewed, by paying special attention to the comparison with other models of baryons, especially the Skyrme model. A careful study of the baryon number and the flavor-singlet axial charge is shown to reveal the special role of valence quarks, which is the core of the standard quark models of baryons but is definitely missing in the skyrmion idea

We discuss the weak transitions of low-lying hyperons in the Skyrme model. It is shown that both the SU(3) Skyrme model and the bound kaon approach to strangeness can derive the il/=1/2 dominance for matrix elements of the currentXcurrent interaction between one-hyperon states, which is. qualitatively similar to the quark model, although the structure of the weak transition amplitudes in the quark model is different from that in the Skyrme model. The vector currents, which are relevant to semileptonic decays, are shown to exhibit a peculiar behavior in the bound kaon .approach. In the strong SU(3)f symmetry breaking lirnit, however, the SU(3) Skyrme model treated in the Yabu-Ando approach turns out to show the same behaviors as those of the bound kaon approach.

It is well known that configuration mixed three quark wavefunctions can explain many aspects of baryons like their spectroscopy, size and structure, decay properties, etc. However, in this work we show that this picture cannot be applied to explain GA of protons simultaneously with the integrated spin-dependent structure function glP. In fact, accepting a value of 1.26 for GAl) we get a lower limit for glP which is quite similar to the one obtained by Preparata and Soffer Z ) and which exceeds the EMC result of 0.114. 3 ) Configuration mixing is essential to explain many facets of baryons. One of its earliest applications was to reproduce the negative mean square charge radius of neutron. 4 ) Glashow has shown 5 ) that an adequate admixture of D-states (~0.25) could reproduce the GA of proton. Semileptonic decays of baryons can also be obtained with similar D-state admixtures. Also Isgur and co-workers have shown that the observed Ez/Ml ratio of the LJ-> Ny transition requires D-state admixtures for theoretical explanations. 6 ) Similarly, the observed value of g/ can also be re­ produced if one uses a large D-state admixture (~0.6). It is also shown that theoreti­ cal estimates of these observables can be made to agree with their experimental values (separately) if one uses relativistic corrections. 7 ) Keeping in view the above successes, several workers have attempted to reproduce GA and g/ within the frame­ work of a single non-relativistic quark model. However, they have failed. In the present work we take a closer look at this problem and show for the first time that it is impossible to reproduce these two quantities simultaneously using a single NRQM. The problem is non-trivial and the interest in these two quantities stems from the fact that they do not depend upon the space wavefunctions. Hence their theoretical estimates are relatively free of the uncertainties due to the choice of the model. In fact, the following analysis is completely free of any such choice and depends only on the standard assumptions of all NRQM. The total wavefunction of three quarks in a nucleon can be written as 8 ),9)