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We consider as an example the two-pion decay of the ρ meson, the 3 S1 q $$ \bar q $$ state of the constituent quarks—the decay being determined by the transition q $$ \bar q $$ → ππ contains information about confinement interactions. One can specify in this decay two types of transitions: (i) the bremsstrahlung radiation of a pion q → q + π (or $$ \bar q $$ → $$ \bar q $$ + π) with a subsequent fusion q $$ \bar q $$ → π, and (ii) the direct transition q $$ \bar q $$ → ππ. We demonstrate how in the amplitudes of the corresponding transitions the quark singularities have to disappear, i.e., what is the way the quark confinement at relatively short distances can be realized. We calculate and estimate the contributions of processes with bremsstrahlung radiation of the pion and of the direct transition q $$ \bar q $$ → ππ. The estimates demonstrate that the processes involving the direct transition q $$ \bar q $$ → ππ are necessary, but they cannot be determined unambiguously by the decay ρ(775) → ππ. We conclude that for the determination of the q $$ \bar q $$ → ππ transition more complete data on the resonance decays into the ππ channels are needed than those available at the moment. [ABSTRACT FROM AUTHOR]

The two-photon decay widths of scalar mesons σ(600), f0(980), and a0(980) are calculated in the framework of the local Nambu-Jona-Lasinio model. The contributions of the quark loops (Hartree-Fock approximation) and the meson loops (next 1/ N c approximation, where N c is the number of colors) are taken into account. These contributions, as we show, are the values of the same order of magnitude. For the f0 decay the K-loop contribution turns out to play the dominant role. The results are in satisfactory agreement with modern experimental data. [ABSTRACT FROM AUTHOR]

Some very unusual features of the hadron structure functions, obtained in generalized QCD sum rules, like the surprisingly strong difference between longitudinally and transversally polarized ρ-meson structure functions and the strong suppression of the gluon sea in the longitudinally polarized ρ meson, are discussed. [ABSTRACT FROM AUTHOR]

On the basis of the assumption of quark-hadron duality, it is shown that the color-singlet contribution to the cross sections for the processes e + g → e + J/ψ + g and gg → J/ψg increases upon taking into account the relative motion of quarks in the J/ψ meson. [ABSTRACT FROM AUTHOR]

It is shown that, as in the case of light mesons, heavy-quarkonium states lie, to a high precision, on Regge trajectories in the ( n, M 2) and ( M 2, J) planes with a universal slope. Specifically, $$c\bar c$$ states are described to a high precision by linear trajectories. For $$b\bar b$$ states, there is no such linearity but, as in the other cases, there is a universal quantum-number dependence of the trajectory. [ABSTRACT FROM AUTHOR]

Results of recent studies that indicate that allowance for the relative motion of quarks in mesons leads to an increase in the cross sections for the process e + e − → J/ ψη c are confirmed. It is shown that the same effect also leads to an increase in the width of scalar and tensor mesons with respect to their decay to two vector mesons, so that the decays χ b0,2 → 2 J/ ψ can be used to observe these mesons at the Tevatron collider and LHC. [ABSTRACT FROM AUTHOR]

Results of recent studies that indicate that allowance for the relative motion of quarks in mesons leads to an increase in the cross sections for the process e + e − → J/ ψη c are confirmed. It is shown that the same effect also leads to an increase in the width of scalar and tensor mesons with respect to their decay to two vector mesons, so that the decays χ b0,2 → 2 J/ ψ can be used to observe these mesons at the Tevatron collider and LHC. [ABSTRACT FROM AUTHOR]

The rare radiative leptonic decays B0d,s → ℓ+ℓ–γ are studied. The contributions to the respective amplitude from the emission of photons from the quark loop, bremsstrahlung from leptons, and weak-annihilation effects are taken into account in relevant calculations. Results are presented for the partial widths and distributions of leptons in the final state. It is shown that the previously disregarded contributions of vector resonances associated with virtual-photon emission from the light valence quark of the B meson have a significant effect on the mass spectra of dileptons.© 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]

The Bethe–Salpeter equations for quark–antiquark composite systems with different quark masses, such as qs (with q = u,d ), qQ, and sQ (with Q = c,b), are written in terms of spectral integrals. For mesons characterized by the mass M, spin J, and radial quantum number n, the equations are written for the (n, M2) trajectories with fixed J. The mixing between states with different quark spin S and angular momentum L is also discussed.© 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]

The transverse-momentum spectra of direct J/psi; arid psi;' mesonis in pp interactions at the Tevatron collider energy of √ 8 = 1.8 TeV are calculated on the basis of nonrelativistic QCD, the fragmentation model, the kT-factorization approach, arid the standard parton model. The contribution of gluon fragmentation is shown to exceed the contribution of c-quark fragmentation both within the parton model arid within the kT-factorization approach. Experimental data of the CDF Collaboration agree with the assumption that gluon fragmentation plays a dominant role in the QQ [³3 S1, 8] octet state, with the nonperturbative matrix element taking approximately equal values in the parton model arid in the kT- factorization approach. [ABSTRACT FROM AUTHOR]

This article presents information related to forthcoming books on nuclear physics published in the December 2004 issue of "Physics of Atomic Nuclei." Few of the listed books are: "Exclusive Production of Charmed-Meson Pairs," A. V. Berezhnoy and A. K. Likhoded; "Pion Electromagnetic Form Factor in QCD Sum Rules," by V. V. Braguta and A. I. Onishchenko; "Subthreshold Photofission of Even Nuclei," by S. G. Kadmensky and L. V. Rodionova; "Application of the Salpeter Equation to Describing Quark Antiquark Interaction," by I. V. Mokrov.

We show on gauge invariance grounds that a new threshold phenomenon has been discovered in the radiative decays φ → γa0 → γπ0η and φ → γf0 → γπ0π0. This enables us to conclude that production of the light scalar mesons a0(980) and f0(980) in these decays is caused by the four-quark transitions, resulting in strong restrictions on the large-Nc expansions of the decay amplitudes. The analysis shows that these constraints give new evidence in favor of the four-quark nature of a0(980) and f0(980) mesons.© 2004 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

We calculate the processes Ds+ → π+ss and Ds+ → π+resonance, respectively, in the spectator and W-annihilation mechanisms. The data on the reaction Ds+ → π+ρ0, which is due to the W-annihilation mechanism only, point to a negligibly small contribution of the W annihilation to the production of scalar–isoscalar resonances Ds+ → π+f0. As to spectator mechanism, we evaluate the 13P0ss component in the resonances f0(980), f0(1300), and f0(1500) and broad state f0(1200–1600) on the basis of data on the decay ratios (Ds+ → π+f0)/(Ds+ → π+φ). The data point to a large ss component in the f0(980): 40 ≲ ss ≲ 70%. Nearly 30% of the 13P0ss component flows to the mass region 1300–1500 MeV, being shared by f0(1300), f0(1500), and broad state f0(1200–1600): the interference of these states results in a peak near 1400 MeV with the width around 200 MeV. Our calculations show that the yield of the radial-excitation state 23P0ss is relatively suppressed, Γ(Ds+ → π+(23P0ss))/Γ(Ds+ → π+(13P0ss)) <= 0.05.© 2004 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

Masses and interactions of light mesons are described in the framework of the model with the chiral invariant SU (2)×SU (2) four-quark interaction. The nonlocal kernel of the interaction is chosen in the form that ensures the absence of ultraviolet divergences in the Feynman diagrams and poles in the quark propagator. Within this model, we demonstrate that, in the chiral limit, the pion mass equals zero and the Goldberger–Treiman relation is fulfilled. The sigma-meson mass and the widths of strong decays σ →ππ , ρ →ππ are estimated.© 2004 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

The light hadron spectrum as computed in nonperturbative QCD is reviewed and compared to lattice data and experiment. The mixing of mesons, hybrids, and glueballs is calculated in the field correlator method. The strong decay mechanisms are found in the method and compared to the known phenomenological models. The role of sea quarks (unquenched approximation) is studied analytically, using radially excited mesons as an example, and compared to experiment. © 2004 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

The low-temperature relations for the trace of the energy–momentum tensor in QCD with two and three quarks are obtained. It is shown that the temperature derivatives of the anomalous and normal (quark massive term) contributions to the trace of the energy–momentum tensor in QCD are equal to each other in the low-temperature region. Leading corrections connected with ππ interaction and thermal excitations of K and η mesons are calculated.© 2004 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

The process γ[sup *]γ → σ is investigated in the framework of the SU(2) × SU(2) chiral NJL model. The form factor of the process is derived for arbitrary virtuality of γ[sup *] in the Euclidean kinematic domain. The asymptotic behavior of this form factor resembles the asymptotic behavior of the γ[sup *]γ → π form factor.© 2003 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

The deep-inelastic production of J/ψ mesons in electron–proton interactions at the HERA collider is considered within the semihard (k[sub T]-factorization) QCD approach and within the color-singlet model. The dependence of the Q[sup 2], p[sub T][sup 2], z, y[sup *], and W distributions of J/ψ mesons on various sets of unintegrated gluon distributions and the dependence of the spin parameter α on p[sub T][sup 2] and Q[sup 2] are investigated. The results of the calculations are compared with the latest experimental data obtained by the H1 and ZEUS Collaborations at the HERA collider. It is shown that experimental investigations of the polarization properties of J/ψ mesons over the kinematical region Q[sup 2] < 1 GeV[sup 2] may provide an additional test of the statement that the dynamics of gluon distributions is governed by the Balitsky–Fadin–Kuraev–Lipatov equations.© 2003 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

On the basis of the decay couplings f[SUB0] ππ, K&Kmacron;, ηη, ηeta;' found earlier in the study of analytical (IJ[SUPPC]= 00[SUP++]) amplitude in the mass range 450-1900 MeV, we analyze the quark-gluonium content of the resonances f[SUB0](980), f[SUB0](1300), f[SUB0](1500), and f[SUB0] (1750) and the broad state f[SUB0](1420) [SUB-70,SUP+150]. The K-matrix technique used in the analysis makes it possible to evaluate the quark-gluonium content both for the states with switched-off decay channels (bare states, (f[SUB0,SUPbare]) and for the real resonances. We observe a significant change in the quark-gluonium composition in the evolution from bare states to real resonances, which is due to the mixing of states in the transitions f[SUB0] (m[SUB1]) → real mesons &rarr f[SUB0] (m[SUB2]) responsible for the)decay processes as well. For f[SUB0](980), the analysis confirmed the dominance of q&qmcrn; component, thus proving the n&nmcr;/s&smacr; composition found in the study of the radiative decays. For the mesons f[SUB0] (1300), f[SUB0](1500), and f[SUB0](1750), the hadronic decays do not allow one to determine uniquely the n&nmcr; s&smacr;, and gluonium components, providing relative percentage only. The analysis shows that the broad state f[SUB0] (1420[SUB-70,SUP+150]) can mix with the flavor singlet q&qmac; component only, which is consistent with gluonium origin of the broad resonance. [ABSTRACT FROM AUTHOR]