Parton energy loss due to synchrotron-like gluon emission

A quasiclassical theory of the synchrotron-like gluon radiation has been developed. The calculations show that the parton energy loss due to the synchrotron gluon emission may be important in the jet quenching phenomenon if the plasma instabilities generate a sufficiently strong chromomagnetic field. The resulting gluon spectrum disagrees with that obtained by Shuryak and Zahed within the Schwinger’s proper time method. The article is published in the original.     

Multiargument recormalization of a gluon field

An extension of traditional renormalization methods that assigns each element of Feynman diagrams an individual evolution parameter is considered. It is shown that conditions necessary for such an extension to be valid are satisfied in quantum gluodynamics.     

Quark and gluon condensates in a magnetic field

The two-loop expression for the vacuum energy density in a constant magnetic field is obtained on the basis of the chiral perturbation theory. The dependence of the quark and gluon condensates on the field intensity H is found. Pis’ma Zh. éksp. Teor. Fiz. 70, No. 11, 711–717 (10 December 1999)     

Coherent vector gluon field in hadrons

A vector cohesive field in a hadron is treated in the classical limit. An asymptotic boson mass spectrum is derived, which becomes linear for infinitely heavy quarks. The size of the wave functions are scaled by the bare quark mass.     

Searches for self-consistent vacuum states of a gluon field

Physics of Atomic Nuclei - A theory of a non-Abelian gauge field is considered on the basis of an effective Lagrangian that possesses the property of asymptotic freedom. In this theory, the...     

Parton physics from large-momentum effective field theory

Parton physics,when formulated as light-front correlations,are difficult to study non-perturbatively,despite the promise of lightfront quantization.Recently an alternative approach to partons have been proposed by re-visiting original Feynman picture of a hadron moving at asymptotically large momentum.Here I formulate the approach in the language of an effective field theory for a large hadron momentum P in lattice QCD,LaMET for short.I show that using this new effective theory,parton properties,including light-front parton wave functions,can be extracted from lattice observables in a systematic expansion of 1/P,much like that the parton distributions can be extracted from the hard scattering data at momentum scales of a few GeV.     

Structure of a confining gluon string within the field correlator method

Physics of Atomic Nuclei - The structure of the chromoelectric string in the Euclidian formulation of Yang-Mills theory is studied by using multipoint correlation functions involving Wilson loop...     

Temperature dependence of a gluon condensate in a model with a spherically symmetric non-Abelian field

The single-loop approximation is used to calculate a gluon condensate in an external spherically symmetric non-Abelian chromomagnetic field. Moscow Institute of Radio Engineering, Electronics, and Automation. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 18–22, July, 1997.     

Photon propagation in a supercritical magnetic field

We show that, for the asymptotically strong (super-Schwinger) magnetic field B exceeding the critical value B_cr=m²c³/eh=4.4×10¹³G, the vacuum polarization effects become important not only in the γ-range, but also for softer electromagnetic quanta, including X-rays and optical photons, and for electromagnetic waves of radio frequencies. This is a consequence of the linearly growing term ?B/B_cr present in the vacuum polarization in an asymptotically strong magnetic field. The results may be essential in studying reflection, refraction, and splitting of X-rays, light and radio waves by magnetic fields of magnetars, and in considering emission of such waves by charged particles.     

Magnetic field propagation in a stellar dynamo

Numerical simulations of stellar dynamos are reviewed. Dynamic dynamo models solve the nonlinear, three-dimensional, time-dependent, magnetohydrodynamic equations for the convective velocity, the thermodynamic variables, and the generated magnetic field in a rotating, spherical shell of ionized gas. When the dynamo operates in the convection zone, the simulated magnetic fields propagate away from the equator in the opposite direction inferred from the solar butterfly diagram. When simulated at the base of the convection zone, the fields propagate in the right direction at roughly the right speed. However, owing to the numerical difficulty, a full magnetic cycle has not been simulated in this region. As a result, it is still uncertain where and how the solar dynamo operates.     

Neutrino propagation in a medium with a magnetic field

Data on the mean multiplicity of strange hadrons produced in minimum bias proton-proton and central nucleus-nucleus collisions at momenta between 2.8 and 400 GeV/c per nucleon have been compiled. The multiplicities for nucleon-nucleon interactions were constructed. The ratios of strange particle multiplicity to participant nucleon as well as to pion multiplicity are larger for central nucleus-nucleus collisions than for nucleon-nucleon interactions at all studied energies. The data at AGS energies suggest that the latter ratio saturates with increasing masses of the colliding nuclei. The strangeness to pion multiplicity ratio observed in nucleon-nucleon interactions increases with collision energy in the whole energy range studied. A qualitatively different behaviour is observed for central nucleus-nucleus collisions: the ratio rapidly increases when going from Dubna to AGS energies and changes little between AGS and SPS energies. This change in the behaviour can be related to the increase in the entropy production observed in central nucleus-nucleus collisions at the same energy range. The results are interpreted within a statistical approach. They are consistent with the hypothesis that the Quark Gluon Plasma is created at SPS energies, the critical collision energy being between AGS and SPS energies.     

Meanvalue picture and ‘equivalent potential’ for a stochastic gluon background field

The main results (energy spectrum and the wave function at the origin) of a model with a stochastic gluon background field — the model of Dosch and Marquard — are alternatively achieved by the so-called meanvalue picture. In this approach it is not necessary to know the details of the stochastic process, therefore the formulas in this meanvalue picture emerge very simply. A local ‘equivalent potential’ to the stochastic process is deduced which reproduces with high accuracy the results of Dosch and Marquard for all values of the gluon correlation time. At last we compare this ‘equivalent potential’ with the well-known linear potential of Eichten et al.     

Gauge and Lorentz covariant quark propagator in an arbitrary gluon field

The quark propagator in the presence of an arbitrary gluon field is calculated gauge and Lorentz covariantly order by order in terms of powers of the gluon field and its derivatives. The result is independent of the path connecting the ends of the propagator, and the leading order result coincides with the exact propagator in the trivial case of a vanishing gluon field. Received: 5 February 2003 / Published online: 23 May 2003     

Shear viscosity in a gluon gas

The relation of the shear viscosity coefficient to the recently introduced transport rate is derived within relativistic kinetic theory. We calculate the shear viscosity over entropy ratio eta/s for a gluon gas, which involves elastic gg-->gg perturbative QCD (PQCD) scatterings as well as inelastic gg<-->ggg PQCD bremsstrahlung. For alpha_{s}=0.3 we find eta/s=0.13 and for alpha_{s}=0.6, eta/s=0.076. The small eta/s values, which suggest strongly coupled systems, are due to the gluon bremsstrahlung incorporated.     

Parton evolution as a branching process

The evolution of parton distributions in high-energy scattering is described using the methods of branching processes. Exclusive, inclusive and multiplicity distributions can be simply obtained from a functional form of the evolution equations. Previous results derived from leading logarithmic terms in perturbation theory are verified. As a new application, we calculate the multiplicity distribution of partons with momenta above a given cutoff.     

Parton distributions in hadrons

We use the statistical model of Zhang et al. [Y.-J. Zhang, B. Zhang, B.-Q. Ma, Phys. Lett. B 523 (2001) 260; Y.-J. Zhang, B.-S. Zou, L.-M. Yang, Phys. Lett. B 528 (2002) 228; Y.-J. Zhang, W.-Z. Deng, B.-Q. Ma, Phys. Rev. D 65 (2002) 114005] to calculate parton distributions in hadrons. The model does reasonably well in predicting the distributions of partons in the proton, including the excess in the proton sea. We extend the model to calculate quark and gluon distributions in the pion, kaon, lambda and the pentaquark. The hadrons are described in terms of a Fock expansion in quark and gluon states. Detailed balance between each pair of states is assumed, from which the coefficients of the Fock state expansion are determined. The parton distribution functions are found in the hadron rest frame from a Monte Carlo calculation. The results are evolved to appropriate QCD scales for comparison with experiment. This project has included significant participation by undergraduates at Seattle University, made possible by support from the Research in Undergraduate Institutions Program of the National Science Foundation.     

Ultrashort pulse propagation in carbon nanotubes in a magnetic field

The problem of ultra-short optical pulse behavior in a system of carbon nanotubes with an applied magnetic field parallel to the nanotube axis was considered. The electromagnetic field was explored using the Maxwell equations. The electronic system of the carbon nanotubes was a quantum system and was mechanically investigated for the case of low temperatures. The distributional pattern of the ultra short pulses and their collision were established by means of numerical modeling.