QCD and Hadron Dynamics

Perturbative QCD predicts and describes various features of multihadron production. An amazing similarity between observable hadron systems and calculable underlying parton ensembles justifies the attempts to use the language of quarks and gluons down to small momentum scales, to approach the profound problems that are commonly viewed as being entirely non-perturbative.Comment: Talk at the Royal Society meeting "Structure of Matter", London, May 200

Interplay of spin-orbit coupling and Zeeman splitting in the absorption lineshape of 2D fermions

We suggest that electron spin resonance (ESR) experiment can be used as a probe of spinon excitations of hypothetical spin-liquid state of frustrated antiferromagnet in the presence of asymmetric Dzyaloshinskii-Moriya (DM) interaction. We describe assumptions under which the ESR response is reduced to the response of 2D electron gas with Rashba spin-orbit coupling. Unlike previous treatments, the spin-orbit coupling, \Delta_{SO}, is not assumed small compared to the Zeeman splitting, \Delta_Z. We demonstrate that ESR response diverges at the edges of the absorption spectrum for ac magnetic field perpendicular to the static field. At the compensation point, \Delta_{SO}\approx \Delta_Z, the broad absorption spectrum exhibits features that evolve with temperature, T, even when T is comparable to the Fermi energy.Comment: 11 pages, 6 figure

Large Rapidity Gap Processes in Proton-Nucleus Collisions

The cross sections for a variety of channels of proton-nucleus interaction associated with large gaps in rapidity are calculated within the Glauber-Gribov theory. We found inelastic shadowing corrections to be dramatically enhanced for such events. We employ the light-cone dipole formalism which allows to calculate the inelastic corrections to all orders of the multiple interaction. Although Gribov corrections are known to make nuclear matter more transparent, we demonstrate that in some instances they lead to an opaqueness. Numerical calculations are performed for the energies of the HERA-B experiment, and the RHIC-LHC colliders.Comment: 19 page

Role of the Nuclear and Electromagnetic Interactions in the Coherent Dissociation of the Relativistic 7^7Li Nucleus into the 3^3H + 4^4He Channel

The differential cross section in the transverse momentum $Q$ and a total cross section of $(31\pm4)$ mb for the coherent dissociation of a 3-A-GeV/$c$ $^7$Li nucleus through the $^3$H$+^4$He channel have been measured on emulsion nuclei. The observed $Q$ dependence of the cross section is explained by the predominant supposition of the nuclear diffraction patterns on light (C, N, O) and heavy (Br, Ag) emulsion nuclei. The contributions to the cross section from nuclear diffraction ($Q\le400$ MeV/$c$) and Coulomb $(Q\le50$ MeV/$c$) dissociations are calculated to be 40.7 and 4 mb, respectively.Comment: ISSN 0021-3640, Pleiades Publishing, Ltd., 200

Solar neutrinos and grand unification

We consider the Grand Unification (GU) scenario for neutrino masses which is based on the see-saw mechanism with the mass of the heaviest right handed (RH) neutrino at the GU-scale: $M_3 \sim \Lambda_{GU}$, and on the quark-lepton symmetry for fermions from the third generation. The scenario predicts for the light neutrinos: $m_3 \sim (2 - 4) \cdot 10^{-3}$ eV and $m_2 \sim (0.3 - 3) \cdot 10^{-5}$ eV (in the case of a linear mass hierarchy of the RH neutrinos or/and in presence of the Planck scale suppressed non-renormalizable operators). It also predicts large $\nu_e - \nu_{\mu}$ mixing: $~\sin^2 2\theta_{e\mu} \stackrel{_>}{_\sim} 0.2$. In this scenario the solar neutrinos ($\nu_{\odot}$) undergo both the \nue $\to$ \nutau resonance conversion in the Sun and substantial \nue $\to$ \numu vacuum oscillations on the way from the Sun to the Earth. The interplay of both effects enlarges the range of neutrino parameters which solve the $\nu_{\odot}$-problem. In particular, $\nu_e - \nu_{\tau}$ mixing angle can be as small as the corresponding quark mixing: $\sin^2 2\theta_{e\tau} \geq (2~-~5) \cdot 10^{-4}$. The scenario predicts peculiar (oscillatory) distortion of the boron neutrino energy spectrum and seasonal variations of signals. Manifestations of these effects in the Super-Kamiokande and SNO experiments are studied.Comment: 36 pages, LaTeX, includes 14 figures, revised and expande

Universal Pion Freeze-out in Heavy-Ion Collisions

Based on an evaluation of data on pion interferometry and on particle yields at mid-rapidity, we propose a universal condition for thermal freeze-out of pions in heavy-ion collisions. We show that freeze-out occurs when the mean free path of pions lambda_f reaches a value of about 1 fm, which is much smaller than the spatial extent of the system at freeze-out. This critical mean free path is independent of the centrality of the collision and beam energy from AGS to RHIC.Comment: 5 pages, 3 figures, revised version resubmitted to PR

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

The crossover from propagating to strongly scattered acoustic modes of glasses observed in densified silica

Spectroscopic results on low frequency excitations of densified silica are presented and related to characteristic thermal properties of glasses. The end of the longitudinal acoustic branch is marked by a rapid increase of the Brillouin linewidth with the scattering vector. This rapid growth saturates at a crossover frequency Omega_co which nearly coincides with the center of the boson peak. The latter is clearly due to additional optic-like excitations related to nearly rigid SiO_4 librations as indicated by hyper-Raman scattering. Whether the onset of strong scattering is best described by hybridization of acoustic modes with these librations, by their elastic scattering (Rayleigh scattering) on the local excitations, or by soft potentials remains to be settled.Comment: 14 pages, 6 figures, to be published in a special issue of J. Phys. Condens. Matte

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

Condensed Matter Theory of Dipolar Quantum Gases

Recent experimental breakthroughs in trapping, cooling and controlling ultracold gases of polar molecules, magnetic and Rydberg atoms have paved the way toward the investigation of highly tunable quantum systems, where anisotropic, long-range dipolar interactions play a prominent role at the many-body level. In this article we review recent theoretical studies concerning the physics of such systems. Starting from a general discussion on interaction design techniques and microscopic Hamiltonians, we provide a summary of recent work focused on many-body properties of dipolar systems, including: weakly interacting Bose gases, weakly interacting Fermi gases, multilayer systems, strongly interacting dipolar gases and dipolar gases in 1D and quasi-1D geometries. Within each of these topics, purely dipolar effects and connections with experimental realizations are emphasized.Comment: Review article; submitted 09/06/2011. 158 pages, 52 figures. This document is the unedited author's version of a Submitted Work that was subsequently accepted for publication in Chemical Reviews, copyright American Chemical Society after peer review. To access the final edited and published work, a link will be provided soo