1,985 research outputs found
Hyperon Enhancement in the Dual Parton Model
We review the two sources of hyperon enhancement in the dual parton model:
strings originating from diquark-antidiquark pairs in the nucleon sea and net
baryons containing two or three sea quarks with a yield controlled by the
observed stopping. We show that adding final state interactions (including
strangeness exchange reactions as well as the inverse reactions required by
detailed balance) with a single averaged cross-section mb, we can
explain the observed hyperon enhancement in PbPb collisions at CERN SPS.Comment: 6 pages, 2 eps-figure
Multiplicity and Transverse Energy Distributions Associated to Rare Events in Nucleus-Nucleus Collisions
We show that in high energy nucleus-nucleus collisions the transverse energy
or multiplicity distribution P_C, associated to the production of a rare,
unabsorbed event C, is universally related to the standard or minimum bias
distribution P by the equation , with and or n. Deviations from this formula are discussed,
in particular having in view the formation of the plasma of quarks and gluons.
This possibility can be distinguished from absortion or interaction of
comovers, looking at the curvature of the over Drell-Yan pairs as a
function of E_T.Comment: 8 pages, 4 Postscript figure
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
Nuclear Structure Functions at Small x from Inelastic Shadowing and Diffraction
Nuclear structure functions at small x and small or moderate are
studied using the relation with diffraction on nucleons which arises from
Gribov's Reggeon Calculus. A reasonable description of experimental data is
obtained with no fitted parameters. A comparison with other models and
predictions for future lepton-ion colliders are provided. Consequences for the
reduction of multiplicities in nucleus-nucleus collisions at energies of RHIC
and LHC are examined.Comment: LaTeX, 32 pages, 14 eps figures included using epsfig; 1 reference
update
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
Production Associated to Rare Events in High Energy Hadron-Hadron Collisions
At very high energy the same universal relation between the multiparticle or
the transverse energy distribution associated to a rare event , and
the corresponding minimum bias distribution P, , or works for nucleus-nucleus collisions as well as
for hadron-hadron collisions. This suggests that asymptotically, all hadronic
processes are similar.Comment: 9 pages, 4 Postscript figure
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
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