1,762 research outputs found
Forward-Backward Multiplicity Correlations in Au+Au Collisions at = 200 Gev
The study of correlations among particles produced in different rapidity
regions may provide understanding of the mechanisms of particle production.
Correlations that extend over a longer range are observed in hadron-hadron
interactions only at higher energies. Results for short and long-range
multiplicity correlations (Forward-Backward) are presented for Au+Au collisions
at = 200 GeV. The growth of long range correlations are
observed as a function of the pseudorapidity gap in central Au+Au collisions.
The Dual Parton model and Color Glass Condensate phenomenology have been
explored to understand the origin of long range correlations.Comment: 8 pages, 4 figures, IWCF06, Hangzhou, China, Nov. 21-24, 200
High energy Scattering in 2+1 QCD: A Dipole Picture
A dipole picture of high energy scattering is developed in the 2+1
dimensional QCD, following Mueller. A generalized integral equation for the
dipole density with a given separation and center of mass position is derived,
and meson-meson non-forward scattering amplitude is therefore calculated. We
also calculate the amplitude due to two pomeron exchange, and the triple
pomeron coupling. We compare the result obtained by this method to our previous
result based on an effective action approach, and find the two results agree at
the one pomeron exchange level.Comment: minor typos corrected. Postscript files are available through
anonymous ftp quark.het.brown.edu, in the directory /pub/preprints, file name
is 9407299. Hard copy is available upon reques
Nuclear Shadowing and Diffraction
The relation between diffraction in lepton-proton collisions and shadowing of
nuclear structure functions which arises from Gribov inelastic shadowing, is
described. A model realizing such relation, which produces a parameter-free
description of experimental data on nuclear structure functions at small ,
is presented. The application to the description of multiplicities in nuclear
collisions is discussed and related to other approaches.Comment: LaTeX, 6 pages, 5 eps figures, uses enclosed ws-ijmpa.cls; invited
talk given by N. Armesto at the Eighth Workshop on Non-Perturbative Quantum
Chromodynamics, Paris, France, June 7th-11th 200
A model-independent analysis of the dependence of the anomalous J/psi suppression on the number of participant nucleons
A recently published experimental dependence of the J/psi to Drell-Yan ratio
on the measured, by a zero degree calorimeter, forward energy E_ZDC in Pb+Pb
collisions at the CERN SPS is analyzed. Using a model-independent approach it
is shown that the data are at variance with an earlier published experimental
dependence of the same quantity on the transverse energy of neutral hadrons
E_T. The discrepancy is related to a moderate centrality region: 100 < N_p <
200 (N_p is the number of participant nucleons) and is peculiar only to the
data obtained within the `minimum bias' analysis (using the `theoretical
Drell-Yan'). This could result from systematic experimental errors in the
minimum bias sample. A possible source of the errors is discussed.Comment: 10 pages, LaTeX, 3 PS-figures. V2: Misprints are correcte
Deep Inelastic Scattering Data and the Problem of Saturation in Small-x Physics
We investigate the role of unitarization effects in virtual photon-proton
(\gamma^*p) interactions at small x. The q\bar{q}-fluctuation of the initial
photon is separated into a small distance and a large distance component and a
model for the unitarization of each component is proposed. The Born
approximation for the small size component is calculated using QCD perturbation
theory. Reggeon diagram technique is used in order to obtain a self-consistent
scheme for both total \gamma^*p cross section and diffractive production. The
model gives a good description of HERA data in the small-x region, with a
single Pomeron of intercept 1.2.Comment: 27 pages, 8 postscript figure
Coherent J/psi production - a novel feature at LHC?
Energy dependence of heavy quarkonia production in hadron-nucleus collisions
is studied in the framework of the Glauber-Gribov theory. We emphasize a change
in the space-time picture of heavy-quark state production on nuclei with
energy. Longitudinally ordered scattering of a heavy-quark system takes place
at low energies, while with increasing energy it transforms to a coherent
scattering of projectile partons on the nuclear target. The characteristic
energy scale for this transition depends on masses and rapidities of produced
particles. For J/psi, produced in the central rapidity region, the transition
happens at RHIC energies. The parameter-free calculation of J/psi in dAu
collisions is in good agreement with recent RHIC data. We use distributions of
gluons in nuclei to predict suppression of heavy quarkonia at LHC.Comment: 13 pages, 4 figures; experimental data and reference included,
conclusions unchanged; to appear in Phys. Lett.
Multiplicity fluctuations in the string clustering approach
We present our results on multiplicity fluctuations in the framework of the
string clustering approach. We compare our results --with and without
clustering formation-- with CERN SPS NA49 data. We find a non-monotonic
behaviour of these fluctuations as a function of the collision centrality,
which has the same origin as the observed fluctuations of transverse momentum:
the correlations between the produced particles due to the cluster formation.Comment: 16 pages, 4 figures, revte
Nonlinear Stability of Static N\'eel Walls in Ferromagnetic Thin Films
In this paper, the nonlinear (orbital) stability of static 180^\circ N\'eel
walls in ferromagnetic films, under the reduced wave-type dynamics for the
in-plane magnetization proposed by Capella, Melcher and Otto [CMO07], is
established. It is proved that the spectrum of the linearized operator around
the static N\'eel wall lies in the stable complex half plane with non-positive
real part. This information is used to show that small perturbations of the
static N\'eel wall converge to a translated orbit belonging to the manifold
generated by the static wall.Comment: 45 page
Charmonium dynamics in dA and AA at RHIC and LHC
We discuss features of charmonium suppression at \sqtr{s} = 200 GeV within
the framework of the Glauber-Gribov theory and the comovers interaction model.
The latter approach has been extended by allowing for secondary charmonium
production due to recombination of pairs in the medium, estimated
from pp data at the same bombarding energy. Centrality and rapidity dependence
of the nuclear modification factor for J/psi in d+Au, Cu+Cu and Au+Au
collisions at RHIC are reproduced without fitting a single model parameter. A
strong suppression of J/psi is predicted for LHC energies.Comment: 4 pages, 4 figures, proceedings from Quark Matter 200
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