Search

For several years the data on different pp(J[sup PC] = 0[sup –+]) → 3 mesons channels presented by the Crystal Barrel collaboration were successfully analyzed by extracting the leading amplitude singularities—pole singularities—with the aim of obtaining information about two-meson resonances. But these analyses do not take three-body final-state interactions into account in an explicitly correct way. This paper is devoted to the consideration of this problem. It is shown how the coupled three-body equations could be written for the π[sup 0]π[sup 0]π[sup 0], ηπ[sup 0]π[sup 0], ηηπ[sup 0], and KKπ[sup 0] channels in the pp annihilation at rest using the three-body dispersion-relation N/D method.© 2003 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

The N[sub c] dependence of PPPγ vertices, where P is a pseudoscalar meson and N[sub c] is the number of colors, is analyzed with allowance for the N[sub c] dependence of the quark charges. It is shown that the reactions Kγ → Kπ and π[sup ±]γ → π[sup ±]η and the decay η → π[sup +]π[sup –]γ are the best processes for determining N[sub c]. The cross section σ(π[sup –]γ → π[sup –]η) as measured by using the VES facility at IHEP agrees with the value of N[sub c] = 3.© 2003 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

In a nonlocal U(3) x U(3) chiral quark model with the local 't Hooft interaction, the first radial excitations of scalar mesons are described. Simple Lorentz-covariant form factors, having a polynomial form in the momentum space, are used for the description of radially excited states. Due to the chiral symmetry, the form factors for scalar states coincide with those for pseudoscalars. As a result, using the experimental values for the masses of pseudoscalar mesons, we predict the mass spectrum of the ground and radially excited scalar-meson states. The scalar glueball is introduced into the effective meson Lagrangian by means of the dilaton model. It is shown that 19 scalar states with masses from 0.4 to 1.7 GeV can be interpreted as two scalar nonets and a glueball. Strong decay widths of scalar mesons are calculated. The state f[sub 0](1500) is shown to be the most probable candidate for the scalar glueball. [ABSTRACT FROM AUTHOR]

The initial stage of a phenomenological analysis of experimental data on the η meson photoproduction off nucleons in the energy range from the threshold to 1.1 GeV is carried out based on a linear nonparametric model. The goal of this stage of the analysis is to obtain statistically reliable information about the partial waves that form the main characteristics of the process. The analysis uses the data of three laboratories about the angular distributions of η-mesons and their E and T asymmetries. The results of the analysis of the angular distributions demonstrate the presence of contradictions in the data obtained by different laboratories. The results of the analysis of the energy dependences of the polarization observables E and T show that the process regime probably changes in the vicinity of 0.9 GeV, which may be caused by the transition from the region of the S[sub 11](1535) and D[sub 13](1520) resonances to the region of the D[sub 15](1675) and F[sub 15](1630) resonances. [ABSTRACT FROM AUTHOR]

The production of charged particles (π[sup ±] mesons and protons) in nucleus-nucleus interactions at energies in the range 3.3-3.7 GeV/nucleon is considered. It is shown that the FRITIOF model adapted to moderately high energies reproduces satisfactorily the energy spectra of mesons emitted into the backward hemisphere in the laboratory frame, as well as their dependence on the masses of colliding nuclei. The FRITIOF model supplemented with the Reggeon model of nuclear breakup allows one to describe the soft part of the spectra of backward-emitted protons. Other approaches are required for describing the hard part of the spectra. [ABSTRACT FROM AUTHOR]

We study interference patterns in the φ →(γa[sub 0] + π[sup 0]ρ) → γπη and φ → (γf[sub 0] + π[sup 0]ρ) → γπ[sup 0]π[sup 0] reactions. Taking into account the interference, we fit the experimental data and show that the background reaction does not distort the π[sup 0]η/spectrum in the decay φ → γπη everywhere over the energy region and does not distort the π[sup 0]π[sup 0] spectrum in the decay φ → γπ[sup 0]π[sup 0] in the wide region of the π[sup 0]π[sup 0]-system invariant mass, m[sub ππ] > 670 MeV, or when the photon energy is less than 300 MeV. We discuss the details of the scalar meson production in the radiative decays and note that there are reasonable arguments in favor of the oneloop mechanism φ → K+K[sup -] → γa[sub 0] and φ → K[sup +]K[sup -] → γf[sub 0]. We also discuss distinctions between the four-quark, molecular, and two-quark models and argue that the Novosibirsk data give evidence in favor of the four-quark nature of the scalar a[sub 0] (980) and f[sub 0] (980) mesons. [ABSTRACT FROM AUTHOR]

For various kinematical domains, the cross section for the diffractive photoproduction of D[sup *] mesons at the HERA ep collider is calculated within a model based on perturbation theory. The results obtained by using different models of the Pomeron are compared. [ABSTRACT FROM AUTHOR]

We present a comparative analysis of three different theoretical approaches to the production of B[sub s] and B[sub c] mesons in high-energy hadron collisions. Our attention focuses on the azimuthal and pseudorapidity correlations between B[sub s] or B[sub c] mesons and accompanying strange or charmed particles. The corresponding kinematical distributions are found to exhibit a high sensitivity to details of the production mechanism and can therefore serve as indicators of interaction dynamics. [ABSTRACT FROM AUTHOR]

A critical consideration of all unusual properties of the scalar a[sub 0](980) and f[sub 0](980) mesons is presented within the four-quark, two-quark, and molecular models. Arguments in favor of the four-quark model are given. Further experiments that could finally resolve this issue are discussed. [ABSTRACT FROM AUTHOR]

The spectra of fast π[sup +] mesons from the π[sup -]A → π[sup +]X reaction on A = [sup 6]Li, [sup 7]Li, and [sup 16]O nuclei at a primary momentum of p[sub 0] = 0.72 GeV/c (T[sub 0] = 0.,59 GeV) are measured at emission-angle values in the range ... = 0°-14°. The results obtained in this way are compared with experimental data taken in other studies at lower energies and with the results of model calculations. The energy dependence of the cross sections and of shadowing effects is analyzed for the reactions in question that occur on lithium isotopes. [ABSTRACT FROM AUTHOR]

The first measurement of the cross sections for D[sup *±]-meson diffractive photoproduction was performed with the ZEUS detector at the HERA ep collider by using an integrated luminosity of 38 pb[sup -1]. The measurement was performed for photon-proton c.m. energies in the range 130 < W < 280 GeV and photon virtualities in the region Q² < 1 GeV². The product D[sup *±] mesons were reconstructed for p[sup D*, sub T] > 2 GeV and -1.5 < η[sup D[sup *]] < 1.5 from the decay channel D[sup *+] → D[sup 0]π[sup +, sub s] with D[sup 0] → K[sup -]π[sup +] (+ c.c.). The diffractive component was selected for 0.001 < x[sub P] < 0.018. The measured cross section in this kinematical range is σ[sup diff, sub ep→ e' D[sup *] X p'] = 0.74±0.21(stat.)[sup 0.27, sub -0.18](syst.) ±0.16(p.diss.) nb (ZEUS preliminary). The measured integrated and differential cross sections are compared with theoretical expectations. [ABSTRACT FROM AUTHOR]

The valence-quark distributions in the π meson and in transversely and longitudinally polarized p mesons in the region of intermediate x are obtained on the basis of generalized QCD sum rules. Powerlaw corrections up to d = 6 are taken into account. The quark distributions in the pion agree with those found from the data on Drell-Yan processes. A comparison of the results for the π and ρ mesons show that polarization effects are very significant and that the distribution functions do not have SU(6) symmetry. [ABSTRACT FROM AUTHOR]

On the basis of the model of hard one-gluon exchange, the two-particle hadronic decays of B[sub c] mesons into S- and P-wave charmonium states, B[sub c] → X[sub cc]-π(ρ), are considered at high momentum transfers and in the nonrelativistic approximation. It is shown that the width with respect to B[sub c]-meson decay into S-wave charmonium states is two times greater than the width with respect to B[sub c]-meson decay into P-wave states and that the yield of J/ψ mesons in the cascade processes of B[sub c]-meson decay via the formation and radiative decay of P-wave charmonium states is approximately 8% of the yield of directly produced J/ψ mesons. [ABSTRACT FROM AUTHOR]

The contribution to the cross section for D[sup *]-meson photoproduction at the HERA accelerator from the scattering of the virtual c&cmacr; vector mesons in the content of the photon on a proton is estimated within the vector-dominance model. It is shown that this mechanism plays an important role throughout the range of D[sup *]-meson transverse momenta available at the HERA facility and that its inclusion significantly improves a theoretical description of the experimental differential distributions. [ABSTRACT FROM AUTHOR]

On the basis of three-point sum rules, the form factors for the semileptonic decays B[sup +][sub c] → B[sub s](B[sup *][sub s])l[sup +]ν[sub l] are calculated with allowance for α[sub s]/υ Coulomb corrections for the heavy quarkonium. Generalized relations associated with spin symmetry within the approach combining heavy-quark effective theory and nonrelativistic QCD are derived for form factors in the region of recoil momenta close to zero. The nonleptonic decays of the B[sub c] meson are studied on the basis of the factorization hypothesis. By summing the main exclusive modes of c-quark decays and by using the results of a previous analysis of b-quark decays, the B[sub c]-meson lifetime is estimated within QCD sum rules and within nonrelativistic QCD. [ABSTRACT FROM AUTHOR]

By including the Z diagram in an analysis performed in the laboratory frame (instantaneous form of dynamics), the notion of quasielastic pion knockout by protons and electrons [(p, 2p) and (e, e'p) reactions treated in terms of the relevant pole diagrams] is generalized to the relativistic case where a meson is quasielastically knocked out of a nucleon by an electron having an energy of a few GeV. The concept of the wave function is introduced for the pion (and for other mesons), and its relation to the vertex constant G[sub π]NN and the vertex function gπNN(k²) is indicated. The spectroscopic factor S[sup BM][sub N] is defined as the normalization of the wave function for the meson M. It is shown by two methods that, under the kinematical conditions of quasielastic knockout that include the condition E[sub π] » m[sub π] (E[sub π] is the energy of the knock-on pion) and the condition that the square Q² of the virtual pion mass is large, the competing tree diagram is suppressed in relation to the pole diagram (this is not so in the case of pion photoproduction). From data of a p(e, e'π[sup +])n, experiment involving longitudinal virtual photons γ[sup *][sub L], the momentum distribution ψ[sup nπ][sub p] (k)² of pions in the nucleon is extracted for the first time over the entire range of significant momenta k, and this result is used to determine the cutoff constant Λ[sub π] = 0.7 GeV/c and the value of S[sup nπ][sub p] ≈ 0.2. The momentum distribution of positive rho mesons in the soft section of the spectrum is determined from experimental data on the process p(e, e'π[sup +])n proceeding through the mechanism p[sup +] + γ[sup *][sub T] → π[sup +] involving transverse photons. A way to determine the momentum distribution of omega mesons through data on the process p(e, e'π[sup 0])p is indicated. Two forms of dynamics—instantaneous form and that of light-front... [ABSTRACT FROM AUTHOR]

The behavior of the inclusive cross sections for the cumulative production of π[sup ±] mesons and protons in pA, DA, and [sup 4]HeA interactions is studied versus the atomic mass number of fragmenting nuclei. The primary-beam momenta were 4.5 GeV/c per nucleon. Secondary pions and protons were recorded with a fixed momentum of 0.5 GeV/c at an angle of 120°. Specifically, the experiment explored the fragmentation of D, He, [sup 6]Li, [sup 7]Li, C, Si, [sup 58]Ni, [sup 64]Ni, [sup 64]Zn, [sup 114]Sn, [sup 124]Sn, and Pb nuclei. The energy spectra of π[sup +] and π[sup -] mesons and protons with momenta in the range 0.3-0.7 GeV/c (the emission angle being 120°) were measured in an 8.9-GeV/c proton beam for Ni, Zn, and Sn isotopes. The special features in the behavior of the cross sections are found and discussed, and a comparison is drawn with the results of other studies. [ABSTRACT FROM AUTHOR]

Within the diffraction theory of multiple scattering, the differential cross sections for elastic and inelastic pion scattering on a [sup 7]Li nucleus are calculated for the case where the final nucleus is either in the ground or in the first excited state. The nuclear wave function is set to that in the αt cluster model. The sensitivity of the calculated observables to variations in the type of the wave functions for the alpha-particle and the triton cluster and for their relative motion is investigated. Various multiplicities of scattering and rescattering on the clusters constituting the [sup 7]Li nucleus are taken into account, and their contributions to the cross section are revealed. The results of the calculations are compared with experimental data at E[sub π] = 143, 164, and 194 MeV. [ABSTRACT FROM AUTHOR]

Charmed-particle production in pp interactions at 70 GeV/c was studied with the SVD setup at the IHEP accelerator (Protvino). The experimental procedure used and the data-selection methods are described. Data obtained by using a quickly cycling bubble chamber and a magnetic spectrometer are analyzed. The number of inelastic-interaction events recorded in the chamber is 109000, with the charge multiplicity being n[sub ch] ≥ 4. The corresponding statistics are 4.96 event/µb. Part of the events were recorded in the magnetic spectrometer. Three three-prong decays of charged particles near the primary vertex are found on the films, two of these being recorded with the spectrometer. All three are interpreted as D[sup -] decays. Two neutral decays observed simultaneously in the chamber and in the spectrometer are interpreted as &Dmacr;[sup 0] decays. The total cross section for c&cmacr; production in the Feynman variable region -1 < x [sub F] < +1 is estimated at σ (c&cmacr;) = 1.6[sup +1.1][sub -0.7](stat.) ± 0.3 (syst.) µb. The cross-section values and the mean values 〈x[sub F]〉 and 〈p&perp〉 for D mesons are compared with other experimental results in the energy range 58-800 GeV. The data of this experiment are compatible with the cross-section estimates obtained in the beam-dump experiment at 70 GeV and with those predicted by perturbative QCD. [ABSTRACT FROM AUTHOR]

Electroweak form factors for the decays of heavy B and D mesons are considered within the covariant formulation of light-front dynamics. With the aid of this approach, it is possible to separate the physical and unphysical contributions to the form factors. An analytic expression is obtained for gluon corrections to the electroweak vertex of the vector and the vector-axial quark current, and it is shown that, for constructing a quantitative description of available experimental data, it is important to take into account such corrections to the decay widths of heavy hadrons. The effect of contact interaction on the transition form factors is analyzed, and the importance of taking into account contact interaction for 0-→1-transitions is demonstrated numerically. The elements V[sub bc], V[sub bu], V[sub cs], and V[sub cd] of the Cabibbo-Kobayashi-Maskawa matrix are determined from an analysis of the entire body of data on 0-→ 0- and 0-→ 1-semileptonic decays. Within the experimental errors, the results obtained in this way are intrinsically consistent and comply with world-averaged data. [ABSTRACT FROM AUTHOR]

We compare two different possibilities of including meson-loop corrections in the Nambu-JonaLasinio model: a strict 1/N[sub c] expansion in the next-to-leading order and a nonperturbative scheme corresponding to a one-meson-loop approximation to the effective action. Both schemes are consistent with chiral symmetry, in particular, with the Goldstone theorem and the Gell-Mann-Oakes-Renner relation. The numerical part at zero temperature focuses on the pion and the p-meson sector. For the latter, meson-loop corrections are crucial in order to include the dominant ρ → ππ-decay channel, while the standard Hartree + RPA approximation only contains unphysical q&qmacr;-decay channels. We find that m[sub π], f[sub π], 〈 &ψmacr; and quantities related to the p-meson self-energy can be described reasonably with one parameter set in the 1/N[sub c].-expansion scheme, whereas we did not succeed in obtaining such a fit in the nonperturbative scheme. We also investigate the temperature dependence of the quark condensate. Here, we find consistency with the chiral perturbation theory to the lowest order. Similarities and differences of both schemes are discussed. [ABSTRACT FROM AUTHOR]

A meson-theoretical model for the reaction πp → π[sup 0]π[sub 0]n for large π[sup -] momenta is developed which treats the final-state interaction between the two produced pions microscopically. For small momentum transfers, the squares of the S-wave amplitudes of the produced two-pion system show a dip for invariant twopion masses in the vicinity of the f[sub 0](980) meson, while for momentum transfers -t > 0.2 (GeV/c)². the f[sub 0](980) meson appears as a bump. The model provides a microscopic explanation of the long-standing puzzle seen by both the GAMS and the BNL experimental collaborations. [ABSTRACT FROM AUTHOR]

The influence of the nucleon-nucleon final-state interaction (FSI) on properties of the meson-production amplitude near threshold is discussed. For nucleon-nucleon interaction, a simple Yamaguchi potential and realistic potential models are considered. It is shown that FSI effects cannot be factorized from the production amplitude. The absolute magnitude of FSI effects depends on the momentum transfer (or on the mass of the produced meson) and hence is not universal. Only in the case of the production of rather heavy mesons like η' or φ FSI do effects become universal. The Jost function approach to FSI effects is critically examined. The influence of the nucleon-nucleon final-state interaction (FSI) on properties of the meson-production amplitude near threshold is discussed. For nucleon-nucleon interaction, a simple Yamaguchi potential and realistic potential models are considered. It is shown that FSI effects cannot be factorized from the production amplitude. The absolute magnitude of FSI effects depends on the momentum transfer (or on the mass of the produced meson) and hence is not universal. Only in the case of the production of rather heavy mesons like η' or φ FSI do effects become universal. The Jost function approach to FSI effects is critically examined. [ABSTRACT FROM AUTHOR]

The cross sections for B-meson production as obtained on the basis of the PYTHIA code and the Quark-Gluon String Model (QGSM) are compared at energies of the proton colliders SPS, Tevatron, and LHC. Model predictions are based on the idea of exchanges of a supercritical Pomeron with phenomenological intercept Δ[sub P](0) = 0.3 for heavy-quark production. The transverse-momentum spectra of B mesons are also compared. It is shown that the cross sections calculated with PYTHIA using CTEQ structure functions are at odds with the asymptotic estimate of the cross sections for B&Bmacr; production within the QGSM. Asymmetries between the spectra of B[sup 0] and &Bmacr;[sup 0] mesons also contradict the PYTHIA result. The reasons for the difference are discussed. [ABSTRACT FROM AUTHOR]

A model that describes the formation of η mesic nuclei in the γ + A → N + [sub η]A' reactions is formulated on the basis of the quasi-free meson photoproduction on nuclei and the concept of a meson-nucleus optical potential. The amplitude of this reaction involving more than four nucleons is obtained in the general form within the nuclear shell model featuring intermediate coupling. The dependences of the cross sections for these reactions on the excitation levels of η mesic nuclei, on the discrete excitation levels of the nucleonic cores of these nuclei, on the type of emitted nucleon, and on the final-state interaction are analyzed for the incident-photon energies from the reaction threshold to 1 GeV. [ABSTRACT FROM AUTHOR]

The distributions of fields generated by static Q&Qmacr; and QQQ sources are calculated analytically within the bilocal approximation of the method of vacuum correlation functions. At large distances between the quarks, the fields assume a clear-cut stringlike shape. The main contribution to the string comes from the longitudinal component of the chromoelectric field. The contribution of the transverse chromoelectric field is below 3% of the contribution from the longitudinal component. A baryonic string has a Y-like shape with a deep well in the region of the string-junction position. Field distributions are considered for a quark-diquark configuration and in the case of three quarks occurring on a straight line. The interaction potential is calculated for three quarks residing at the vertices of an equilateral triangle. [ABSTRACT FROM AUTHOR]

The asymmetry between the spectra of leading and nonleading charmed mesons that was measured in Σ[sup -]A interactions at p[sub L] = 340 GeV/c in the WA89 experiment is described within the Model of Quark-Gluon Strings (QGS model also known as QGSM) under the assumption that there is a fraction of charmed sea quark-antiquark pairs (intrinsic charm) in an interacting hyperon. It is shown that the asymmetries between D[sup -]- and D[sup +]-meson spectra and between D[sup -, sub s]- and D[sup +, sub s] -meson spectra can be approximated by QGSM curves obtained with the same string-fragmentation parameter, a[sup 1] = 10, and the same intrinsic-charm fraction, δ[sub c, &cmarc;] = 0.01, as those that were used in describing D[sup -, sub s]/D[sup +, sub s]-meson asymmetry of π[sup -]A experiments in previous studies. The asymmetry between the spectra of Λ[sub c] and &Λmacr;[sub c] that was measured in Σ[sup -]A collisions at p[sub L] = 600 GeV/c in the E781 experiment is also described within this scheme. The QGSM results are compared with the results of the calculations in the next-to-leading approximation of perturbative QCD that were performed by other authors. [ABSTRACT FROM AUTHOR]

The semileptonic decays of the B[sub c] meson into heavy quarkonia J/ψ(η[sub c]) and a pair of leptons are investigated on the basis of three-point sum rules of QCD and nonrelativistic QCD (NRQCD). Calculations of analytic expressions for the spectral densities of QCD and NRQCD correlation functions with allowance for Coulomb-like α[sub s]/v terms are presented. At recoil momenta close to zero, generalized relations due to the spin symmetry of NRQCD are derived for the B[sub c] → J/ψ (η[sub c]) lv[sub l] form factors, with l denoting one of the leptons (e, μ, or τ). This allows one to express all NRQCD form factors in terms of a single universal quantity, an analog of the Isgur-Wise function at the maximal lepton-pair invariant mass. The gluon-condensate corrections to three-point functions are calculated both in full QCD in the Borel transform scheme and in NRQCD in the moment scheme. This enlarges the parametric-stability region of the sum-rule method, thereby rendering the results of the approach more reliable. Numerical estimates of the widths for the transitions B[sub c] → J/ψ(η[sub c]) lv[sub l] are presented. [ABSTRACT FROM AUTHOR]

Spin effects in the weak two-body hadronic decays of the B[sup c] and B[sup *, sub c] mesons into J/ψ and ρ(π) mesons are considered within the model of hard one-gluon exchange between quarks at high momentum transfers. It is shown that the polarization of the J/ψ meson in the decays of the B[sup *, sub c] meson differs substantially from that in the decays of the B[sub c] meson. The decay widths of the B[sup *, sub c] meson differ significantly from the widths of the B[sub c] meson. [ABSTRACT FROM AUTHOR]

It is shown that the list of unusual mesons that are planned to be studied in photoproduction reactions can be supplemented with I[sup G] (J[sup PC]) = 2[sup +] (2[sup ++]) exotic states X[sup ±](1600), which are natural to seek as manifestations of the ρ[sub ±]ρ[sup 0] decay channels in the reactions γN → ρ[sub ±]ρ[sup 0]N and γN → ρ[sub ±]ρ[sup 0]&Delta A classification of the ρ[sub ±]ρ[sup 0] states according to their quantum numbers is presented. A model for the spin structure of the amplitudes for the reactions γp → ƒ[sub 2](1270)p, γp → a[sub 2][sup 0] (1320)p, and γN → X[sub ±](N, Δ) is proposed, and estimates are obtained for the corresponding cross sections. At E[sub γ] ≈ 6 GeV, it is found that σ(γp → ƒ[sub 2](1270)p) ≈ 0.12 µb, A σ(γp → a[sub 2][sup 0] (1320)p) ≈ 0.25 µb, σ(γN → X[sup ±]N → ρ[sub ±]ρ[sup 0]N) &≈ 0.018 µb, and σ (γp → X[sup -] Δ[sup ++] → ρ[sup -]ρ[sup 0] Δ[sup ++]) ≈ 0.031 µb. The problem of isolating signals from X[sup ±] states against the natural background that is associated with other channels of π[sup ±]π[sup 0]π[sup +]π[sup -] production is discussed. It is deduced that searches for exotic states X[sup ±](2[sup +] (2[sup ++])) in experiments at JLAB will be quite efficient—for example, the yield of about 2.8 x 10[sup 6] events per month is expected to correspond to the estimated cross sections for the reactions γN → X[sup ±]N → ρ[sub ±]ρ[sup 0]N. [ABSTRACT FROM AUTHOR]

The reactions pn → dω) and pn → dφ) are investigated near the corresponding thresholds. The S-wave amplitudes are calculated within the two-step model described by a triangle graph with π, ρ, and ω) mesons in the intermediate state. The cross sections for the reactions pn → dω) and pn → dφ) are predicted to be significantly larger than the cross sections for the corresponding reactions pp → ppω) and pp → ppφ) at the same values of the c.m. excess energy Q. The phi-to-omega yield ratio is found to be (34 ± 10) x 10[sup -3]. [ABSTRACT FROM AUTHOR]

The inclusive K[sup +]-meson production in photon-induced reactions in the near-threshold and subthreshold energy regimes is analyzed for the one-step (γN → K[sup +]Y, Y = Λ, Σ) incoherent production processes on the basis of an appropriate new folding model that takes properly into account the struck-target nucleon-removal energy and the internal momentum distribution (nucleon spectral function), extracted from recent quasielastic-electron-scattering experiments and from many-body calculations based on realistic models of NN interaction. Simple parametrizations of the total and differential cross sections for K[sup +] production in photonnucleon collisions are presented. A comparison of the model calculations of the K[sup +] differential cross sections for γ[sup 12]C interactions in the threshold region with existing experimental data is given, which displays the contributions to K[sup +] production at considered incident energies from the use of the single-particle part, as well as high momentum and high removal energy part, of the nucleon spectral function. Detailed predictions for the K[sup +] total and differential cross sections for γ²H, γ[sup 12]C, and γ[sup 208]Pb interactions at subthreshold and near-threshold energies are provided. The effect of the uncertainties in the elementary K[sup +]-production cross sections on the K[sup +] yield is explored. [ABSTRACT FROM AUTHOR]

The spectra of π[sup -] mesons originating from pC, HeC, CC, and CTa collisions are analyzed in terms of the light-front variables ξ and ζ. The angular and momentum distributions of π[sup -] mesons are studied in various regions of the variables ξ[sup ±] and ζ[sup ±]. These distributions in the regions ξ[sup +] < &ζtilde;[sup +] and ξ[sup +] > &ξtilde;[sup +] do not admit a unified description. In the region ξ[sup +] < &ξtilde;[sup +], the distributions in question are consistent with predictions of the statistical model. The temperature parameter T decreases almost linearly with increasing product of the mass numbers of colliding nuclei (that is, with increasing number of interacting nucleons). The distributions in the region ξ[sup +] > &ξtilde;[sup +] are fitted to semiempirical forms. [ABSTRACT FROM AUTHOR]

The differential and total cross sections for the photoproduction of vector D[sup *] mesons and for their production in deep-inelastic interactions at the HERA collider are estimated on the basis of a model motivated by perturbative calculations within QCD. The proposed model makes it possible to take into account higher twists in the meson transverse momentum at p[sub T] ∼ m[sub c] and to reproduce correctly the dominance of c-quark fragmentation for p[sub T] » m[sub c]. The possibility of the hadronization of an octet c&qmacr; state into a meson is considered, whereby good agreement with experimental data is obtained both for the case of D[sup *]-meson photoproduction and for the case of D[sup *]-meson formation in a deep-inelastic process. [ABSTRACT FROM AUTHOR]

The mean multiplicities of π[sup -] mesons and protons originating from pC, dC, αC, and CC interactions at a momentum of p = 4.2 GeV/c per projectile nucleon and the distributions of these particles in kinematical variables are presented. These experimental distributions are compared with the corresponding predictions obtained on the basis of the FRITIOF model. It is shown that the FRITIOF version used in the present analysis describes satisfactorily our experimental data. [ABSTRACT FROM AUTHOR]

In this paper, we investigate an SU(3) extension of the chiral quark-meson model. The spectra of baryons with strangeness, charm, and bottom are considered within a "rigid oscillator" version of this model. The similarity between the quark sector of the Lagrangian in the model and the Wess-Zumino term in the Skyrme model is noted. The binding energies of baryonic systems with baryon numbers B = 2 and 3 possessing strangeness or heavy flavor are also estimated. The results are in good qualitative agreement with those obtained previously in the chiral soliton (Skyrme) model. [ABSTRACT FROM AUTHOR]

We bosonize the Nambu-Jona-Lasinio quark model with separable nonlocal interactions in order to derive a chiral U(3) × U(3) Lagrangian, containing, besides the usual meson fields, their first radial excitations. The spontaneous breaking of chiral symmetry is governed by the Nambu-Jona-Lasinio gap equation. The first radial excitations of the kaon, K[sup *], and φ are described with the help of two form factors. The decays K[sup *]' → ρK, K[sup *]' → K[sup *]π,K[sup *]' → Kπ, φ', → K[sup *]K, φ' → &Kmacr;K, K' →Kρ, K' → K[sup *]π, and K' → K2π are considered, and a qualitative agreement of our results with the experimental data is found. [ABSTRACT FROM AUTHOR]

An SU(2) × SU(2) chiral quark model describing the properties and interaction of pions and scalar and vector mesons is considered. The confinement of quarks is introduced in the model by means of an infrared cut-off in the one-loop quark diagrams. This cutoff gives rise to the elimination of the unphysical thresholds of the quark-antiquark pair production. The π-a[sub 1] transitions are taken into account. The model conserves all lowenergy theorems. The masses of mesons and the widths of the decays ρ → 2π and σ → 2π are calculated. [ABSTRACT FROM AUTHOR]

A new interpretation of the intrinsic charm phenomenon based on the assumption of the pentaquark $$\left| {uudc\bar c} \right\rangle$$ mixing with a proton is offered. The structure function of the c-quark in the pentaquark is constructed. The mixing ration is evaluated theoretically, using experimental data on the D-meson production and the inclusive production of the hidden charm particles. [ABSTRACT FROM AUTHOR]

A nonlocal chiral quark model is consistently extended beyond mean field using a strict 1/ N expansion scheme. It is found that the 1/ N corrections lead to a lowering of the temperature of the chiral phase transition in comparison with the mean-field result. On the other hand, near the phase transition the 1/ N expansion breaks down and a nonperturbative scheme for the inclusion of mesonic correlations is needed in order to describe the phase transition region. [ABSTRACT FROM AUTHOR]

We study the finite temperature behavior of light scalar and pseudoscalar meson properties in the context of a three-flavor nonlocal chiral quark model. The model includes mixing with active strangeness degrees of freedom, and takes care of the effect of gauge interactions by coupling the quarks with a background color field. We analyze the chiral restoration and deconfinement transitions, as well as the temperature dependence of meson masses, mixing angles, and decay constants. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented which reports on a comparative analysis of the properties of cumulative mesons produced in high-energy proton-nucleus and nucleus-nucleus interactions.

It is shown that if the a[sub 0](980) boson is the scalar chiral partner of a π meson, its contribution to the transition η → πγγ has a value comparable to that originated by vector meson exchange. Together, these two mechanisms give the decay probability consistent with the experimental observation. [ABSTRACT FROM AUTHOR]

Reports on the investigation of the resonance of two meson systems based on experimental data from the spectrometer developed at the Institute of Theoretical and Experimental Physics in Moscow, Russia. Existence of resonance states revealed in the meson systems; Calculation of the effective mass from the measured parameters; Observance of the resonance maxima accumulated by the spectrometer in runs of different durations.

The contributions of the axial-vector and vector resonance states to D → P(V)l&νmacr;[sub l] decays are investigated on the basis of phenomenological chiral Lagrangians. It is shown that inclusion of such intermediate states improves agreement with experimental data. [ABSTRACT FROM AUTHOR]

The amplitude of the decay η → π[sup +]π[sup -]γ is derived in the soft limit of the current scheme of η-η' mixing. The results are compared with experimental values of the phenomenological contribution additive to the p-meson contribution. [ABSTRACT FROM AUTHOR]

The most recent experimental results obtained by studying the X(3872) state in the CLEO-c, LHCb, and BESIII experiments are surveyed, and prospects of its further studies are discussed. [ABSTRACT FROM AUTHOR]