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     

Self-consistent diffraction in the multiperipheral model (IV)

Numerical fits to high-energy proton-proton scattering data are made using formulae obtained previously from a self-consistent solution to the multiperipheral model. Agreement with the total cross section and elastic differential cross section is satisfactory.     

Blueprint XAS: a Matlab‐based toolbox for the fitting and analysis of XAS spectra

Blueprint XAS is a new Matlab‐based program developed to fit and analyse X‐ray absorption spectroscopy (XAS) data, most specifically in the near‐edge region of the spectrum. The program is based on a methodology that introduces a novel background model into the complete fit model and that is capable of generating any number of independent fits with minimal introduction of user bias [Delgado‐Jaime & Kennepohl (2010), J. Synchrotron Rad. 17 , 119–128]. The functions and settings on the five panels of its graphical user interface are designed to suit the needs of near‐edge XAS data analyzers. A batch function allows for the setting of multiple jobs to be run with Matlab in the background. A unique statistics panel allows the user to analyse a family of independent fits, to evaluate fit models and to draw statistically supported conclusions. The version introduced here (v0.2) is currently a toolbox for Matlab. Future stand‐alone versions of the program will also incorporate several other new features to create a full package of tools for XAS data processing.     

Possible evidence for deconfinement in hadron collisions

The collision of hadrons at very high energies produces an entity whose energy density is extremely large resulting in the emission of a large number of hadrons. Though the entity may not have transited into the deconfined parton phase, the very high energy density may cause more than one charged hadron to be emitted at any instant. This yields a new multiplicity distribution, termed the GS distribution which fits the data as well as the popular negative binomial distribution. Neither the GS nor the NB distribution alone agrees with the data beyond 200 GeV, but a weighted sum of GS and NB distributions fits the experimental results exceedingly well. Since the negative binomial distribution arises from the branching of partons, we interpret the increase with energy of the negative binomial component in the weighted sum as the onset of a deconfined phase. The rising cross section for the negative binomial component parallels very closely the inclusive cross section for hadron jets which also is considered a consequence of parton branching.     

Generation of experimental L x‐ray fluorescence cross‐sections for inter‐elements at inter‐energies EL1 ≤ E ≤ EK (computer program IGELCS)

The experimental values of L x‐ray fluorescence (XRF) cross‐sections are not available for all the elements in the range La–U, at all the photon energies E in the range EL1 ≤ E ≤ EK. To generate L XRF cross‐sections, where experimental measurements are not available, two empirical relations have been developed, one between the L XRF cross‐sections and photon energy and the other between the L XRF cross‐sections and atomic number. For the measured data on L XRF cross‐sections at incident energies between Ll and K edges of an element and the data on L XRF cross‐sections for elements in the range 57 ≤ Z ≤ 92 at an energy value, polynomial fits have been derived. The L XRF cross‐section values generated with the derived empirical relations were found to be in agreement with the experimental values within their experimental uncertainties. Subsequently, a software code IGELCS was developed to interpolate and to generate the cross‐sections at inter‐energies and for inter‐elements in a single computer run. The running of the software requires minimum input data on five elements at five common energies. Copyright © 2003 John Wiley & Sons, Ltd.     

High-E T jets and double scattering

The recently found excess of high-E _T jets over the current QCD predictions is attributed to gluon radiation in a double scattering process inside a nucleon. An order-of-magnitude estimate of the cross section fits the experimental findings rather well. The specific features of the process are discussed. Various similar hardronic effects related to the short radiation length are described. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 9, 679–682 (10 May 1996) Published in English in the original Russian journal. Edited by Steve Torstveit.     

<Emphasis Type="Italic">Z</Emphasis>′ signals from the LEP2 data

The LEP2 data on e ⁺ e ⁻ → e ⁺ e ⁻, μ⁺μ⁻, and τ ⁺ τ ⁻ processes are fitted to estimate possible signals of the Abelian Z′ boson. In the many-parametric fits, four independent parameters must be fitted if the derived already low-energy relations between the Z′ couplings to the standard-model fermions are taken into consideration. No signals are found for the complete LEP2 data set for these processes. In the fit of the backward bins, the hint at the 1.25σ C.L. is detected. The Z′ couplings to the vector and axial-vector lepton currents are constrained. Comparisons with the one-parameter fits are performed. The text was submitted by the authors in English.     

The analysis of elastic and inelastic scattering of alpha particles using a folding potential

The elastic and inelastic scattering of alpha particles from Cd and Te isotopes are analysed in terms of a single folding model in which the scattering potential is approximated by folding an effectiveα-nucleon interaction into the mass distribution of the target nuclei. Excellent fits are obtained to the elastic scattering data. However, to obtain equally good fits to inelastic scattering data arbitrary adjustments of the effective interaction are required.     

On the slope of the differential cross section for the photo- and electroproduction of vector mesons

The photo- and electroproduction of ? mesons at high energy is examined in a simple Regge-pole model with q² dependent residues. The behaviour of the differential cross section at t=0 and of its slope, as a function of the q² and of the photon energy, are correlated, and good fits to the data are obtained.     

Electron impact ionization rate coefficients and cross sections for highly ionized iron

Electron impact ionization cross sections for the ions Fe(XVII)-(XXVI) have been computed in a distorted wave exchange approximation. Analytic fits are provided for the cross section data, as well as for the rate coefficients assuming a Maxwellian electron velocity distribution. For ejection of a 2p ground state electron, the scaled ionization rate was found to depend linearly on the number of 2p electrons in the ion.     

Pole expansion of the deuteron vertex functions revisited

New fits to the deuteronS andD state vertex functions are presented using a standard relativistic pole expansion. The new data from electron scattering admit two solutions which should be distinguishable by measuring the tensor polarization ined scattering.This note has been stimulated by discussions with Barbara Badelek. We thank S. Platchkov for providing the Saclay data in numerical form.     

Polarized pK<Superscript>-</Superscript> scattering in Unitary Baryon Chiral Perturbation Theory

We study pK^- scattering in the energy range from threshold through the L \Lambda(1520) peak in UBChPT, taking into account O(q) vertices from meson-baryon contact interactions and s - and u -channel ground-state baryon exchange, s - and u -channel decuplet- and nonet-baryon exchange and t -channel vector-meson exchange, as well as O(q ²) flavor-breaking vertices. Detailed fits to data are presented, including a substantial body of differential cross-section data with meson momentum q _lab > 300 MeV not considered in previous treatments.     

Temperature quenching of intracenter luminescence of Mn<Superscript>2+</Superscript> ions in diluted magnetic semiconductors

The Spectr-W³ database was developed in 2001–2013 and is available online (http://spectrw3. snz.ru). The database contains information on various spectroscopic constants of atoms and ions such as the wavelengths and probabilities of radiative transitions, energy levels of atoms and ions, ionization potentials, autoionization rates, and the parameters of analytical approximation of cross sections and rates of collisional transitions in atoms and ions. Spectr-W³ presently contains around 450 thousand records and is the world’s largest factual database on spectral properties of multicharged ions. A new stage of development of Spectr-W³, which involves adding a new section titled “Emission Spectrograms” to the database, commenced in 2014. In contrast to the already existing sections that contain tabulated data, this new section provides graphical data (with necessary explanatory notes) on the spectrograms of emission of atoms and ions excited in various plasma sources. The structure of sections of the Spectr-W³ database is characterized, and examples of queries and the corresponding search results are given.     

Defect production rates in electron irradiated aluminium

Abstract

The cross section for atomic displacement has been determined at 7.5°K by means of electrical resistivity measurements in electron irradiated aluminium up to transferred energies of 1100 eV. These data and those from the literature have been evaluated with respect to the displacement function (DF). Below 200 eV the DF could be derived from the data with sufficient accuracy by solving the integral equation which describes the displacement cross section. Above 200 eV a family of non-linear and linear DF's has been found which fits the data within the experimental error. From the linear DF's one obtains an average threshold energy of (62±6) eV according to Kinchin and Pease.     

Introduction of the electron repulsion into the molecular orbital wave function

The total MO wave function of a π-electron system contains covalent, total ionic and mixed parts. Taking the electron repulsions explicitly into account, the individual contribution of the parts are revaluated. The ω technique of Streitwieser is critically discussed and reformulated, disinguishing between odd and even numbered ω-electron systems. ω=0·5 (instead of Streitwieser's ω=1·4) fits the experimental data of ethylene reasonably well. This improved ω technique is used for taking the electron repulsions into account.

The new method is applied to ethylene, butadiene, benzene, hexatriene, the allyl cation, the allyl radical and the allyl anion. A substantial improvement of the total π electron energy is achieved.     

Photodetachment of H- near an elastic surface in a magnetic field

This paper investigates the photodetachment of the negative hydrogen ion H near an elastic wall in a magnetic field.The magnetic field confines the perpendicular motion of the electron,which results in a real three-dimensional well for the detached electron.The analytical formulas for the cross section of the photodetachment in the threedimensional quantum well are derived based on both the quantum approach and closed-orbit theory.The magnetic field and the elastic surface lead to two completely different modulations to the cross section of the photodetachment.The oscillation amplitude depends on the strength of the magnetic field,the ion-wall distance and the photon polarization as well.Specially,for the circularly polarized photon-induced photodetachment,the cross sections display a suppressed(E E th) 1/2 threshold law with energy E in the vicinity above Landau energy E th,contrasting with the(E E th) 1/2 threshold law in the presence of only the magnetic field.The semiclassical calculation fits the quantum result quite well,although there are still small deviations.The difference is attributed to the failure of semiclassical mechanics.     

RELATIVISTIC STUDY OF PROTON-NUCLEUS ELASTIC SCATTERING AT LOWER ENERGIES

The Lorentz invariant relativistic optical potential have been discussed at energies below 300MeV.The Dirac equation with scalar and vector potential is solved by exact partial wave method.The calculated results of proton ⁴⁰Ca at energy region 300—65MeV are presented and compared with the experimental data of differential cross section dσ/dΩ,analyzing power A_y(θ) and spin rotation function Q(θ).It is shown that the impoved relativistic optical potential fits the data well.