1,679 research outputs found
Centrality Dependence of Hadron Multiplicities in Nuclear Collisions in the Dual Parton Model
We show that, even in purely soft processes, the hadronic multiplicity in
nucleus-nucleus interactions contains a term that scales with the number of
binary collisions. In the absence of shadowing corrections, this term dominates
at mid rapidities and high energies. Shadowing corrections are calculated as a
function of impact parameter and the centrality dependence of mid-rapidity
multiplicities is determined. The multiplicity per participant increases with
centrality with a rate that increases between SPS and RHIC energies, in
agreement with experiment.Comment: 15 pages, 4 postscript figure
Charged Multiplicities at SPS and RHIC and consequences for suppression
Hadron multiplicities in nucleus--nucleus interactions are calculated in the
Dual Parton Model and its dependence on the number of collisions and the number
of participants is analyzed. Shadowing corrections are calculated as a function
of impact parameter and the multiplicity per participant as a funtion of
centrality is found to be in agreement with experiment at SPS and RHIC
energies. The obtained results are used to compute the suppression in
a comover approach.Comment: 4 pages, 4 postscript figures. Talk given at XXXVI Rencontres de
Moriond, Les Arcs, France, March 200
Baryon and Antibaryon production at RHIC energies in the Dual Parton Model
We compute the mid-rapidity densities of pions, kaons, baryons and
antibaryons in -- collisions at = 130 GeV in the Dual Parton
Model supplemented with final state interactions, and we present a comparison
with available data.Comment: 4 pages, 2 figures. Talk given at XXXVII Rencontres de Moriond, Les
Arcs, France, March 200
Elliptic Flow and Fixed p_T Suppression in a Final State Interaction Model
It has been shown that a final state interaction model, used to describe
J/psi suppression, can also describe the fixed p_T suppression of the pi^0 (and
charged pions) yield at all values of p_T, with a final state interaction
cross-section sigma close to one milibarn. We propose an extension of the model
to the pion motion in the transverse plane - which introduces a dependence of
the suppression on the azimuthal angle theta_R. Using the same value of sigma,
we obtain values of the elliptic flow v_2 close to the experimental ones, for
all values of p_T, including the soft p_T region.Comment: 21 pages, 6 figure
Anomalous suppression of production at large transverse momentum in Au + Au and d + Au collisions at 200 GeV
We propose a model of suppression of large -pions in heavy ion
collisions based on the interaction of the large pion with the dense
medium created in the collision. The model is practically the same as the one
previously introduced to describe suppression. Both the and the
centrality dependence of the data are reproduced. In deuteron-gold collisions,
the effect of the final state interaction with the dense medium turns out to be
negligibly small. Here the main features of the data are also reproduced both
at mid and at forward rapidities.Comment: 20 pages, latex, 3 postscript figures. Last version, to be published
in EJP
Baryon stopping and hyperon enhancement in the improved dual parton model
We present an improved version of the dual parton model which contains a new
realization of the diquark breaking mechanism of baryon stopping. We reproduce
in this way the net baryon yield in nuclear collisions. The model, which also
considers strings originating from diquark-antidiquark pairs in the nucleon
sea, reproduces the observed yields of p and Lambda and their antiparticles and
underestimates cascades by less than 50 %. However, Omega's are underestimated
by a factor five. Agreement with data is restored by final state interaction,
with an averaged cross-section as small as 0.14 mb. Hyperon yields increase
significantly faster than antihyperons, in agreement with experiment.Comment: 40 pages, 18 postscript figure
J/psi suppression at SPS and RHIC in the comovers approach
The NA50 collaboration data on the suppression are compared with the
results obtained in a comovers approach based on the Dual Parton Model (DPM).
Predictions for the suppression versus the charged multiplicity -
measured in the rapidity region of the dimuon trigger - are given for SPS and
RHIC energies.Comment: 4 pages, contribution to QM200
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
Measuring velocity ratios with correlation functions
We show how to determine the ratio of the transverse velocity of a source to
the velocity of emitted particles, using split-bin correlation functions. The
technique is to measure and , subtract the contributions from
the single-particle distribution, and take the ratio as the bin size goes to
zero. We demonstrate the technique for two cases: each source decays into two
particles, and each source emits a large number of particles.Comment: 9 pages, LaTeX, 2 PostScript figure
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