737 research outputs found

### Large Scale Rapidity Correlations in Heavy Ion Collisions

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

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

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($Q^2$) approximation. This implies that the $Q^2$-evolution of
$\Delta G (x, Q^2)$ 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

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

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

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 $F_2(x,Q^2)$. We claim that
the SC in $xG(x,Q^2)$ 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 $\ln(1/x)$ in the
region of very small $x$. 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

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

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

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