124707884
The Decay $\tau \to 3 \pi \nu_\tau$ and Characteristics of $A1$ Meson
The phenomenological meson Lagrangian based on the four-quark interactions of the scalar, pseudoscalar, vector and axial-vector types is used for description of the decay τ−→π+π−π−vτ. The structure of the main hadronic vertexa 1 − ρπ is discussed. The expression for the axial hadronic currentJμ(a1→3π) is obtained. The low-energy limit of this current is analysed. Spectral functions for the main channel of the given process are calculated. The fitting of the experimental data leads to the following values of thea1 parameters: 
 
$$\begin{gathered} m_{a_1 } = 1242 \pm 37MeV,\Gamma _{a_1 } = 465_{ - 143}^{ + 228} MeV\left( {DELCO} \right); \hfill \\ \hfill \\ m_{a_1 } = 1260 \pm 14MeV,\Gamma _{a_1 } = 298_{ - 34}^{ + 40} MeV\left( {MARK II} \right); \hfill \\ \hfill \\ m_{a_1 } = 1250 \pm 9MeV,\Gamma _{a_1 } = 488 \pm 32MeV\left( {ARGUS} \right). \hfill \\ \end{gathered} $$
118014393
QCD analysis of deep inelastic lepton-scattering data
We have carried out a QCD analysis of data on deep inelastic lepton-scattering (using data of the collaborations BCDMS, EMC, and CDHS) in the leading and next-to-leading orders in the coupling constant ..cap alpha../sub s/. We have considered the effect of the sea quarks and gluons. We discuss the dependence of our results for ..lambda.. on effects of twist corrections, nuclear target effects, and heavy-quark production thresholds.
119138207
Lepton flavor violating photoleptonic effect
We study lepton flavor violating analogs of the photoelectric effect, with a final μ or T instead of an electron: γe → μ and γe → T. On the basis of the general parametrization of the matrix element of the electromagnetic current we estimate the upper limits for the cross sections and event rates of these processes, imposed by the current experimental bounds on μ → ey and T → eγ decays.
182432079
SPECTRALITY OF GELL-MANN-LOW FUNCTION
117509698
QCD NUCLEON MODEL WITH RELATIVISTIC OSCILLATOR INTERACTION BETWEEN CONSTITUENT QUARK
896237
Electroproduction of charmonia off nuclei
In a recent publication we have calculated elastic charmonium production in ep collisions employing realistic charmonia wave functions and dipole cross sections and have found good agreement with the data in a wide range of s and Q^2. Using the ingredients from those calculations we calculate exclusive electroproduction of charmonia off nuclei. Here new effects become important, (i) color filtering of the c-cbar pair on its trajectory through nuclear matter, (ii) dependence on the finite lifetime of the c-cbar fluctuation (coherence length) and (iii) gluon shadowing in a nucleus compared to the one in a nucleon. Total coherent and incoherent cross sections for C, Cu and Pb as functions of s and Q^2 are presented together with some differential cross sections. The results can be tested with future electron-nucleus colliders or in peripheral collisions of ultrarelativistic heavy ions.
120068071
Partial-transparency effects in heavy-ion collisions at energies of the order of 1 GeV/nucleon
Abstract A model of heavy-ion collisions at energies E lab ∼ 1 GeV/nucleon taking into account the effects of incomplete statistical equilibrium in highly-excited nuclear matter is presented. The collision process is considered as the interaction of two flows of nucleons decelerating each other. This process is described within the framework of a relativistic kinetic approach employing the Fokker-Planck approximation. Assuming two-flow nonequilibrium the momentum distribution function is represented as a sum of two maxwellian distributions displaced by the average relative velocity of flows. Equations for time evolution of space-averaged velocities and internal energies of flows are derived. These equations contain a single model parameter, i.e. the effective deceleration length λ d . Using the firestreak model geometry inclusive cross sections of protons and composite particles (d, t) in the reactions Ne + NaF, Ar + KCl and Ar + Pb are calculated at various values of E lab . In contrast to the firestreak model, a complete stopping of colliding tubes in the centre-of-mass frame was not assumed in the present calculation. Composite particle spectra are calculated on the basis of the coalescence model. The theory is thoroughly compared with the experimental data. The approach suggested allows us to reproduce a two-humped structure in the rapidity distributions of the secondary particles. The experimental data analysis leads to the value λ d = 8 fm for E lab = 0.8 GeV/nucleon, which is in good agreement with the estimation based on experimental NN cross sections.
121066263
Space-time picture of high-energy heavy-ion collisions and scaling properties of proton spectra
Abstract A comparative analysis of predictions of three typical models of relativistic nucleus-nucleus collisions is performed. It includes the model of partial transparency, the hydrodynamical model and the intranuclear cascade model. The results of proton and pion spectra calculations are compared with the experimental data available at incident energies of 0.8, 2.1 and 3.6 GeV nucleon . The effects of deviation from thermodynamical equilibrium due to mutual transparency of projectile and target nuclei are studied. The importance of the transition layer arising on the boundary of the overlapping parts of interacting nuclei has been demonstrated. The emission from this layer gives the main contribution to inclusive proton spectra in the target fragmentation region. In this region all the three models are in good agreement with experiment and, in particular, reproduce the scaling properties of proton inclusive cross sections satisfactorily. Considerable difference in the models' predictions takes place in the central rapidity region, especially in central collisions of identical nuclei. Experiments are suggested to study the mechanisms of the transition layer formation and the nature of scaling behaviour of proton spectra.
15791609
Renormalization of a gapless Hartree-Fock approximation to a theory with spontaneously broken O ( N ) symmetry
The renormalization of a gapless {phi}-derivable Hartree-Fock approximation to the O(N)-symmetric {lambda}{phi}{sup 4} theory is considered in the spontaneously broken phase. This kind of approach was proposed by three of us in a previous paper [Yu. B. Ivanov, F. Riek, and J. Knoll, Phys. Rev. D 71, 105016 (2005).] in order to preserve all the desirable features of {phi}-derivable Dyson-Schwinger resummation schemes (i.e., validity of conservation laws and thermodynamic consistency) while simultaneously restoring the Nambu-Goldstone theorem in the broken phase. It is shown that unlike for the conventional Hartree-Fock approximation this approach allows for a scale-independent renormalization in the vacuum. However, the scale dependence still persists at finite temperatures. Various branches of the solution are studied. The occurrence of a limiting temperature inherent in the renormalized Hartree-Fock approximation at fixed renormalization scale {mu} is discussed.
118518440
Color path-integral Monte-Carlo simulations of quark-gluon plasma: Thermodynamic and transport properties
Based on the quasiparticle model of the quark-gluon plasma (QGP), a color quantum path-integral Monte-Carlo (PIMC) method for calculation of thermodynamic properties and -- closely related to the latter -- a Wigner dynamics method for calculation of transport properties of the QGP are formulated. The QGP partition function is presented in the form of a color path integral with a new relativistic measure instead of the Gaussian one traditionally used in the Feynman-Wiener path integral. It is shown that the PIMC method is able to reproduce the lattice QCD equation of state at zero baryon chemical potential at realistic model parameters (i.e. quasiparticle masses and coupling constant) and also yields valuable insight into the internal structure of the QGP. Our results indicate that the QGP reveals quantum liquid-like (rather than gas-like) properties up to the highest considered temperature of 525 MeV. The pair distribution functions clearly reflect the existence of gluon-gluon bound states, i.e. glueballs, at temperatures just above the phase transition, while meson-like $q\bar{q}$ bound states are not found. The calculated self-diffusion coefficient agrees well with some estimates of the heavy-quark diffusion constant available from recent lattice data and also with an analysis of heavy-quark quenching in experiments on ultrarelativistic heavy ion collisions, however, appreciably exceeds other estimates. The lattice and heavy-quark-quenching results on the heavy-quark diffusion are still rather diverse. The obtained results for the shear viscosity are in the range of those deduced from an analysis of the experimental elliptic flow in ultrarelativistic heavy ions collisions, i.e. in terms the viscosity-to-entropy ratio, $1/4\pi < \eta/S < 2.5/4\pi$, in the temperature range from 170 to 440 MeV.
125142837
The effect of a hot jet in the hydrodynamic theory of heavy ion collisions