25 research outputs found
Gauge/String-Gravity Duality and Froissart Bound
The gauge/string-gravity duality correspondence opened renewed hope and
possibility to address some of the fundamental and non-perturbative QCD
problems in particle physics, such as hadron spectrum and Regge behavior of the
scattering amplitude at high energies. One of the most fundamental and
long-standing problem is the high energy behavior of total cross-sections.
According to a series of exhaustive tests by the COMPETE group, (1). total
cross-sections have a universal Heisenberg behavior in energy corresponding to
the maximal energy behavior allowed by the Froissart bound, i.e., with and for all reactions,
and (2). the factorization relation among is well satisfied by experiments. I discuss the
recent interesting application of the gauge/string-gravity duality of
correspondence with a deformed background metric so as to break the conformal
symmetry that can lead to the Heisenberg behavior of rising total
cross-sections, and present some preliminary results on the high energy QCD
from Planckian scattering in and black-hole production.Comment: 10 pages, Presented to the Coral Gables Conference 2003, Launching of
BelleE\'poque in High Energy Physics and Cosmology, 17 - 21 December 2003,
Fort Lauderdale, Florid
Bremsstrahlung of a Quark Propagating through a Nucleus
The density of gluons produced in the central rapidity region of a heavy ion
collision is poorly known. We investigate the influence of the effects of
quantum coherence on the transverse momentum distribution of photons and gluons
radiated by a quark propagating through nuclear matter. We describe the case
that the radiation time substantially exceeds the nuclear radius (the relevant
case for RHIC and LHC energies), which is different from what is known as
Landau-Pomeranchuk-Migdal effect corresponding to an infinite medium. We find
suppression of the radiation spectrum at small transverse photon/gluon momentum
k_T, but enhancement for k_T>1GeV. Any nuclear effects vanish for k_T > 10GeV.
Our results allow also to calculate the k_T dependent nuclear effects in prompt
photon, light and heavy (Drell-Yan) dilepton and hadron production.Comment: Appendix A is extended compared to the version to be published in
Phys.Rev.
Transparent Nuclei and Deuteron-Gold Collisions at RHIC
The current normalization of the cross section of inclusive high-pT particle
production in deuteron-gold collisions measured RHIC relies on Glauber
calculations for the inelastic d-Au cross section. These calculations should be
corrected for diffraction. Moreover, they miss the Gribov's inelastic shadowing
which makes nuclei more transparent (color transparency). The magnitude of this
effect rises with energy and it may dramatically affect the normalization of
the RHIC data. We evaluate these corrections employing the light-cone dipole
formalism and found a rather modest corrections for the current normalization
of the d-Au data. The results of experiments insensitive to diffraction
(PHENIX, PHOBOS) should be renormalized by about 20% down, while those which
include diffraction (STAR), by only 10%. Such a correction completely
eliminates the Cronin enhancement in the PHENIX data for pions. The largest
theoretical uncertainty comes from the part of the inelastic shadowing which is
related to diffractive gluon radiation, or gluon shadowing. Our estimate is
adjusted to data for the triple-Pomeron coupling, however, other models do not
have such a restrictions and predict much stronger gluon shadowing. Therefore,
the current data for high-pT hadron production in d-Au collisions at RHIC
cannot exclude in a model independent way the possibility if initial state
suppression proposed by Kharzeev-Levin-McLerran. Probably the only way to
settle this uncertainty is a direct measurement of the inelastic d-Au cross
sections at RHIC. Also d-Au collisions with a tagged spectator nucleon may
serve as a sensitive probe for nuclear transparency and inelastic shadowing. We
found an illuminating quantum-mechanical effect: the nucleus acts like a lens
focusing spectators into a very narrow cone.Comment: Latex 50 pages. Based on lectures given by the author at Workshop on
High-pT Correlations at RHIC, Columbia University, May-June, 2003. The
version to appear in PR
Dynamical and thermal descriptions in parton distribution functions
We suggest a duality between the standard (dynamical) and statistical
distributions of partons in the nucleons. The temperature parameter entering
into the statistical form for the quark distributions is estimated. It is found
that this effective temperature is practically the same for the dependence on
longitudinal and transverse momenta and, in turn, it is close to the freeze-out
temperature in high energy heavy-ion collisions.Comment: 8 pages, 1 figure. Talk given at the 6th International Workshop on
Critical Point and Onset of Deconfinement (CPOD), JINR, Dubna, 23-29 August
201
Spontaneous breaking of four-fold rotational symmetry in two-dimensional electronic systems explained as a continuous topological transition
The Fermi liquid approach is applied to the problem of spontaneous violation
of the four-fold rotational point-group symmetry () in strongly correlated
two-dimensional electronic systems on a square lattice. The symmetry breaking
is traced to the existence of a topological phase transition. This continuous
transition is triggered when the Fermi line, driven by the quasiparticle
interactions, reaches the van Hove saddle points, where the group velocity
vanishes and the density of states becomes singular. An unconventional Fermi
liquid emerges beyond the implicated quantum critical point.Comment: 6 pages, 4 figure
The QCD description of diffractive processes
We review the application of perturbative QCD to diffractive processes. We
introduce the two gluon exchange model to describe diffractive qq(bar) and
qq(bar)g production in deep inelastic scattering. We study the triple Regge
limit and briefly consider multiple gluon exchange. We discuss diffractive
vector meson production at HERA both at t = 0 and large |t|. We demonstrate the
non-factorization of diffractive processes at hadron colliders.Comment: 39 pages, 14 figures, LaTeX, new references added and some discussion
clarifie
Quasiparticles of strongly correlated Fermi liquids at high temperatures and in high magnetic fields
Strongly correlated Fermi systems are among the most intriguing, best
experimentally studied and fundamental systems in physics. There is, however,
lack of theoretical understanding in this field of physics. The ideas based on
the concepts like Kondo lattice and involving quantum and thermal fluctuations
at a quantum critical point have been used to explain the unusual physics.
Alas, being suggested to describe one property, these approaches fail to
explain the others. This means a real crisis in theory suggesting that there is
a hidden fundamental law of nature. It turns out that the hidden fundamental
law is well forgotten old one directly related to the Landau---Migdal
quasiparticles, while the basic properties and the scaling behavior of the
strongly correlated systems can be described within the framework of the
fermion condensation quantum phase transition (FCQPT). The phase transition
comprises the extended quasiparticle paradigm that allows us to explain the
non-Fermi liquid (NFL) behavior observed in these systems. In contrast to the
Landau paradigm stating that the quasiparticle effective mass is a constant,
the effective mass of new quasiparticles strongly depends on temperature,
magnetic field, pressure, and other parameters. Our observations are in good
agreement with experimental facts and show that FCQPT is responsible for the
observed NFL behavior and quasiparticles survive both high temperatures and
high magnetic fields.Comment: 17 pages, 17 figures. Dedicated to 100th anniversary of A.B.Migdal
birthda
Hadronization in Z0 decay
The confinement transition from the quark and gluon degrees of freedom
appropriate in perturbation theory to the hadrons observed by real world
experiments is poorly understood. In this strongly interacting transition
regime we presently rely on models, which to varying degrees reflect possible
scenarios for the QCD dynamics. Because of the absence of beam and target
remnants, and the clean experimental conditions and high event rates, e+e-
annihilation to hadrons at the Z0 provides a unique laboratory, both
experimentally and theoretically, for the study of parton hadronization. This
review discusses current theoretical understanding of the hadronization of
partons, with particular emphasis on models of the non-perturbative phase, as
implemented in Monte Carlo simulation programs. Experimental results at LEP and
SLC are summarised and considered in the light of the models. Suggestions are
given for further measurements which could help to produce more progress in
understanding hadronization.Comment: Topical review, to appear in J.Phys.G, 80 page