737 research outputs found

    Large Scale Rapidity Correlations in Heavy Ion Collisions

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    We discuss particle production mechanisms for heavy ion collisions. We present an argument demonstrating how the fluctuations of the number of produced particles in a series of classical emissions can account for KNO scaling. We predict rapidity correlations in the particle production in the event by event analysis of heavy ion collisions on the rapidity scales of the order of one over the strong coupling constant.Comment: REVTeX, 13 pages, 3 figure

    Field-Induced Magnetization Steps in Intermetallic Compounds and Manganese Oxides: The Martensitic Scenario

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    Field-induced magnetization jumps with similar characteristics are observed at low temperature for the intermetallic germanide Gd5Ge4and the mixed-valent manganite Pr0.6Ca0.4Mn0.96Ga0.04O3. We report that the field location -and even the existence- of these jumps depends critically on the magnetic field sweep rate used to record the data. It is proposed that, for both compounds, the martensitic character of their antiferromagnetic-to-ferromagnetic transitions is at the origin of the magnetization steps.Comment: 4 pages,4 figure

    A Property of Recombination in Polarized Hadronic Targets

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    The triple gluon-ladder vertex is shown to project the outgoing gluon in either polarization state with equal probability up to the leading double-ln(x)ln(Q2Q^2) approximation. This implies that the Q2Q^2-evolution of ΔG(x,Q2)\Delta G (x, Q^2) is free from recombination effects to this level of approximation.Comment: latex, 6 pages AZPH-TH/92-29 Phys. Rev D 50 in press 199

    Large Rapidity Gaps in PP Collisions

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    The survival probability of large rapidity gaps in pp collisions is calculated for several different eikonal models of the Gaussian form. Results obtained for models based on partonic interactions are quite similar. The Regge-pole model predicts a higher value of .Comment: 11 pages, TAUP 2030-93 (LaTeX, two figures not attached, available from authors

    Scaling violation and shadowing corrections at HERA

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    We study the value of shadowing corrections (SC) in the HERA kinematic region in the Glauber{ Mueller approach. Since the Glauber{Mueller approach was proven in perturbative quantum chromodynamics (QCD) in the double-logarithmic approximation (DLA), we develop the DLA approach for the deep inelastic structure function which takes into account the SC. Our estimates show small SC for F2 in the HERA kinematic region while they turn out to be sizable for the gluon structure function. We compare our estimates with those for gluon distribution in leading order (LO) and next to leading order (NLO) in the DGLAP evolution equations

    Parton Densities in a Nucleon

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    In this paper we re-analyse the situation with the shadowing corrections (SC) in QCD for the proton deep inelastic structure functions. We reconsider the Glauber - Mueller approach for the SC in deep inelastic scattering (DIS) and suggest a new nonlinear evolution equation. We argue that this equation solves the problem of the SC in the wide kinematic region where \as \kappa = \as \frac{3 \pi \as}{2 Q^2R^2} x G(x,Q^2) \leq 1. Using the new equation we estimate the value of the SC which turn out to be essential in the gluon deep inelastic structure function but rather small in F2(x,Q2)F_2(x,Q^2). We claim that the SC in xG(x,Q2)xG(x,Q^2) is so large that the BFKL Pomeron is hidden under the SC and cannot be seen even in such "hard" processes that have been proposed to test it. We found that the gluon density is proportional to ln⁥(1/x)\ln(1/x) in the region of very small xx. This result means that the gluon density does not reach saturation in the region of applicability of the new evolution equation. It should be confronted with the solution of the GLR equation which leads to saturation.Comment: latex file 53 pages, 27 figures in eps file

    The Role of Screening Corrections in High Energy Photoproduction

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    The role of screening corrections, calculated using the eikonal model, is discussed in the context of soft photoproduction. We present a comprehensive calculation considering the total,elastic and diffractive cross sections jointly. We examine the differences between our results and those obtained from the supercritical Pomeron-Reggeon model with no unitarity corrections.Comment: 12 pages (Replacement due to PostScript file problem in previous posting

    Shadowing Corrections in Diffractive QCD Leptoproduction of Vector Mesons

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    The formulae for shadowing corrections in deep inelastic leptoproduction of vector mesons are presented. These formulae are also applicable for photoproduction of vector mesons constituted of heavy quarks. Our results are conveniently presented by the definition of a damping factor giving the reduction of the calculated cross sections due to shadowing. Our calculated cross sections are compared with those obtained with no shadowing and with the available experimental data including the recent data from HERA. We have also investigated the importance of shadowing on the relationship between \frac{\pa F_2(Q^2,x)}{ \pa ln Q^2} and the cross section for virtual photoproduction of vector mesons. A discussion of shadowing corrections to the proton's gluon density is presented and numerical estimates are given.Comment: 22 pages, 14 figures in eps file