High-energy QCD as a topological field theory

We propose an identification of the conformal field theory underlying Lipatov's spin-chain model of high-energy scattering in perturbative QCD. It is a twisted N = 2 supersymmetric topological field theory, which arises as the limiting case of the SL(2,R)/U(1) non-linear model that also plays a role in describing the Quantum Hall effect and black holes in string theory. The doubly-infinite set of non-trivial integrals of motion of the high-energy spin-chain model displayed by Faddeev and Korchemsky are identified as the Cartan subalgebra of a bosonic sub-symmetry possessed by this topological theory. The renormalization group and an analysis of instanton perturbations yield some understanding why this particular topological spin-chain model emerges in the high-energy limit, and provide a new estimate of the asymptotic behaviour of multi-Reggeized-gluon exchange. Received: 31 August 1998 / Published online: 11 March 1999     

The Escape Rate of a Molecule

We show existence and give an implicit formula for the escape rate of the n-centre problem of celestial mechanics for high energies. Furthermore we give precise computable estimates of this rate. This exponential decay rate plays an important role especially in semiclassical scattering theory of n-atomic molecules. Our result shows that the diameter of a molecule is measurable in a (classical) high-energy scattering experiment.     

The spin and flavour dependence of high-energy photoabsorption

We analyse the low x, low Q ² polarised photoabsorption data from SLAC and use this data to make a first estimate of the high-energy part of the Drell-Hearn-Gerasimov sum-rule. The present status of spin dependent Regge theory is discussed. Received: 23 October 1998     

高能重离子碰撞中的J/ψ反常抑制现象

对NA50合作组给出的入射动量为158A GeV/c的Pb-Pb碰撞中的J/ψ反常抑制现象进行了分析.在J/ψ的核与随动者吸收理论基础上，假设了QGP相变在对心Pb-Pb碰撞中的产生及QGP环境对J/ψ粒子100%的吸收效应，从而改进了高能重离子碰撞中的J/ψ微分产生截面，理论较好地解释了实验结果. 关键词： J/ψ反常抑制')" href="#">J/ψ反常抑制 核吸收 随动者 夸克-胶子等离子体     

Heavy-quark hadroproduction in k T -factorization approach with unintegrated gluon distributions

We consider the processes of heavy-quark production using the unintegrated gluon distributions. The numerical predictions for high-energy nucleon-nucleon and photon-nucleon collisions of the k _T -factorization approach (semihard theory) are compared with the experimental data from the Tevatron collider and HERA. The total production cross sections and pT distributions are considered and they are in reasonable agreement with the data for reasonable values of QCD scale. The text was submitted by the authors in English.     

Tunable near-infrared optical properties of three-layered gold–silica–gold nanoparticles

The absorption spectra of gold–silica–gold nanoshells have been investigated by using Mie theory with variation of the geometry. With an increase in core radius the plasmon resonance for the lower energy mode ω ₋⁻ shows a distinct redshift while for the high-energy mode ω ₋⁺ shows a blueshift. It is surprising that with increasing middle layer thickness the resonance of ω ₋⁻ mode blueshifts first and then redshifts. In addition, an increase of the dielectric constant of the middle layer is found to reduce the resonance energies of the particle. The tunable near-infrared optical properties are discussed in terms of plasmon hybridization theory.     

Mg2Si晶体结构及消光特性的研究

基于高能X射线的散射理论,研究了Mg₂Si晶体的结构和消光特性.结果表明,Mg₂Si晶体具有反萤石结构,当衍射指数H,K和L奇偶混合时其散射光就会出现系统消光,而当衍射指数H,K和L全为偶数或者全为奇数时,其散射光就会出现衍射.在实际应用中对研究具有反萤石结构的晶体具有重要意义. 关键词： 散射理论 消光特性 反萤石结构 衍射     

Helium ionization with excitation of the atom accompanied by absorption and scattering of high-energy photons

We calculate analytically the cross sections for ionization of the helium atom with absorption and scattering of high-energy photons. The electrons are assumed to be moving in the Coulomb field of the nucleus. The electron-electron interaction is taken into account in the first order of perturbation theory. The high-frequency limits for the ratios of these cross sections to the single-electron ionization cross sections are obtained for s-excitations in absorption and for s-and p-excitations in scattering. Zh. éksp. Teor. Fiz. 111, 862–870 (March 1997)     

Roy–Steiner equations for <Emphasis Type="Italic">γγ</Emphasis>→<Emphasis Type="Italic">ππ</Emphasis>

Starting from hyperbolic dispersion relations, we derive a system of Roy–Steiner equations for pion Compton scattering that respects analyticity, unitarity, gauge invariance, and crossing symmetry. It thus maintains all symmetries of the underlying quantum field theory. To suppress the dependence of observables on high-energy input, we also consider once- and twice-subtracted versions of the equations, and identify the subtraction constants with dipole and quadrupole pion polarizabilities. Based on the assumption of Mandelstam analyticity, we determine the kinematic range in which the equations are valid. As an application, we consider the resolution of the γγ→ππ partial waves by a Muskhelishvili–Omnès representation with finite matching point. We find a sum rule for the isospin-two S-wave, which, together with chiral constraints, produces an improved prediction for the charged-pion quadrupole polarizability (a₂-b₂)^p±=(15.3±3.7)×10^-4(\alpha_{2}-\beta_{2})^{\pi^{\pm}}=(15.3\pm3.7)\times 10^{-4} fm⁵. We investigate the prediction of our dispersion relations for the two-photon coupling of the σ-resonance Γ _σγγ . The twice-subtracted version predicts a correlation between this width and the isospin-zero pion polarizabilities, which is largely independent of the high-energy input used in the equations. Using this correlation, the chiral perturbation theory results for pion polarizabilities, and our new sum rule, we find Γ _σγγ =(1.7±0.4) keV.     

Double ionization and excitation ionization in the Compton scattering of high-energy photons for metastable states of heliumlike ions

Double ionization and excitation ionization in Compton scattering for heliumlike ions in metastable states are investigated. The electron energy distribution for double ionization and the total cross sections for both processes are calculated. The calculations are carried out in the zeroth order of perturbation theory with respect to electron-electron interaction, using Coulomb wave functions as the first approximation. The resulting equations are valid only in the high-energy nonrelativistic range. It is assumed that Z≫1, but αZ≪1 (Z is the charge of the nucleus, and α is the fine-structure constant). Zh. éksp. Teor. Fiz. 116, 1889–1902 (December 1999)     

Exclusive radiativeB-decays in the light-cone QCD sum rule approach

We discuss vector, axial-vector, scalar and pseudoscalar two-point functions at low and intermediate energies. We first review what is known from chiral perturbation theory, as well as from a heat kernel expansion within the context of an extended Nambu-Jona-Lasinio (ENJL) model. We derive then these two-point functions to all orders in the momenta and to leading order in 1/N _c within the framework of this model. We find an improved high-energy behaviour and a general way of parametrizing them that shows relations between some of the two-point functions, which are also valid in the presence of gluonic interactions. The similarity between the shape of the experimentally known spectral functions and the ones we derive, is greatly improved with respect to those predicted by the usual constituent quark like models. We also obtain the scalar massM _s =2M _Q independent of the regularization scheme. In the end, we calculate fully an example of a nonleptonic matrix element in the ENJL-model, theπ ⁺?π ⁰ electromagnetic mass difference and find good agreement with the measured value.

     

Statistics of low-frequency pulsations in critical regimes of heat mass exchange with phase transitions

Experimental investigation of fluctuation dynamics in critical and transitional modes of heat mass exchange shows existence of irregular high-energy pulsations with power spectrum inversely proportional to the frequency—so called 1/f spectrum. Such regimes are characterized by the fact that an essential part of the pulsations energy is connected with very slow processes and mean that large high-energy bursts are possible in the system. Another characteristic feature of such regimes is scale invariance of the fluctuations distribution function. According to the theory, the 1/f fluctuations can emerge in physical systems due to simultaneous phase transitions in presence of sufficiently intensive white noise. This paper is devoted to detailed investigation of relaxation processes at steadying of stationary stochastic process in non-equilibrium phase transitions in system of two nonlinear stochastic differential equation. Such an information reveals statistical patterns of particular large-scale low-frequency bursts. Discontinuous “forgetting” of the initial conditions takes place. It is shown by numerical methods that distributions of duration and maximal values of the low-frequency extreme bursts have the power-like form. Experimental investigation results of statistical characteristics of fluctuation processes at ultrasonic cavitation and flash boiling of overheated water jets are presented. Results of the experiments carried out fit conclusions of the theoretical model for interacting heterogeneous phase transitions.     

The superconducting properties of Cu-doped MgB2 bulks prepared by a high-energy milling method

The Cu-doped MgB₂ bulks were prepared by a high-energy milling and subsequent sintering method. Compared to the pure and Cu-doped bulks prepared only by sintering, the critical current density (J_c) of the milled Cu-doped samples was improved with a slight decrease in critical transition temperature (T_c). Using the phase analysis and microstructure observation, it has been found that the MgB₂ grains in the milled Cu-doped sample was refined with the high-energy milling and thus provided more grain boundary pinning, which was contributed to the improvement of J_c at high field.     

Scaling of 1/<Emphasis Type="Italic">f</Emphasis> noise in nonequilibrium phase transitions

Investigation of the dynamics of fluctuations of heat and mass transfer reveals that its crisis and transient modes exhibit high-energy pulsations with a power spectrum that is inversely proportional to frequency (flicker or 1/f fluctuations). Such a spectrum suggests energy transfer from high-to low-frequency modes and the possibility of large-scale catastrophic outbursts in the system being considered. The theory shows that such fluctuations arise in the system owing to the simultaneous occurrence of interacting phase transitions in the presence of white noise having a sufficiently high intensity. The distribution of fluctuations for scale transformations of the set of stochastic equations that describe the generation of 1/f noise is investigated. It is shown that, under a scale transformation, the Gaussian distribution of a random process having a 1/f spectrum passes to an exponential distribution, which is characteristic of the statistics of extreme outbursts. The probability of such outbursts must be taken into account in predicting the stability of various heat-transfer modes.     

Solutions of independent DGLAP evolution equations for the gluon distribution and singlet structure functions in the next-to-leading order at low x

We present a set of independent formulas to extract the gluon distribution and the singlet structure function from its derivatives with respect to lnQ ² in the next-to-leading order of perturbation theory at low x based on a hard Pomeron exchange. In this approach, both singlet quarks and gluons have the same high-energy behavior at small x. This approach requires the QCD input parameterizations for independent DGLAP evolutions, which we calculated numerically and compared with the MRST, GRV, and DL models. The Pomeron has a hard nature. Its evolution gives a good fit to the experimental data. The values obtained are in the range 10⁻⁴ ≤ x ≤ 10⁻² at Q ² = 20 GeV². The text was submitted by the author in English.     

The early high-energy afterglow emission from short GRBs

We calculate the high energy afterglow emission from short Gamma-Ray Bursts (SGRBs) in the external shock model. There are two possible components contributing to the high energy afterglow: electron synchrotron emission and synchrotron self-Compton (SSC) emission. We find that for typical parameter values of SGRBs, the early high-energy afterglow emission in 10 MeV-10 GeV is dominated by synchrotron emission. For a burst occurring at redshift z = 0.1, the high-energy emission can be detectable by Fermi LAT if the blast wave has energy E ⩾ 10⁵¹ ergs and the fraction of electron energy ɛ _e ⩾ 0.1. This provides a possible explanation for the high energy tail of SGRB 081024B.

     

Effect of the ionization energy loss density of high-energy bismuth,krypton, and xenon ions on the development of hydrogen blisters in silicon

Radiation-induced athermal hydrogen removal from single-crystal silicon subjected to irradiation by high-energy heavy Bi⁺ (E = 710 MeV), Kr⁺ (E = 85 and 250 MeV), and Xe⁺ (130 MeV) ions is detected experimentally. The decrease in the hydrogen concentration depends on the specific ionization energy losses of high-energy heavy ions. At high specific ionization losses of Bi⁺ ions with E = 710 MeV (22.5 keV/nm), the hydrogen concentration decreases to a level at which blisters cannot be observed in an optical or electron microscope (which is likely to be 1 at % hydrogen at the peak of the calculated hydrogen concentration profile). At medium specific ionization losses of Xe⁺ ions with E = 130 MeV (12.5 keV/nm) and Kr⁺ ions with E = 250 and 85 MeV (9.5 and 8.5 keV/nm, respectively), the hydrogen concentration decreases to a level that does not affect blister formation but determines the blister failure (flaking) conditions.     

Independent electron theory of multiple ionization of xenon by intense laser pulses

The intensity dependence of the multiphoton ionization spectra of Xe atoms has been investigated with an improved accuracy and well-controlled laser parameters. In particular, we have examined the ionization rates for X³⁺, X²⁻, X⁺ as functions of the laser intensity and the pressure in the target chamber. The apparatus used for these measurements is characterized by a high-energy resolution (better than 200 meV) and a completely digital acquisition system. The time-of-flight spectra clearly show the contributions of the different isotopes present in Xe gas. The laser pulses have been characterized with great accuracy by monitoring the energy, pulse width and divergence shot by shot. The ionization rates of the different ions have been used for testing the basic assumption of the Geltman theory of multiple ionization based on the single electron ionization model. We have found that for the small intensity range investigated the quantity (dXe ⁺/dI)·(dXe ³⁺/dI)/(dXe ²⁺/dI)² appears to be quite close to the value 0.5 predicted by this model.