2,015 research outputs found
The Primakoff effect on a proton target
Primakoff effect offers us with a way to determine the radiative decay width
of pseudo-scalar mesons when they are photo-produced in the electromagnetic
field of hadronic systems. Taking advantage of recent developments in the Regge
description of the production of mesons in the strong hadronic field, this
paper evaluates the relative importance of the electromagnetic and the strong
amplitudes, and assesses the possibilities which become opened by modern
experimental facilities.Comment: 4 pages; 5 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
Diffractive Dissociation in Deep Inelastic Scattering at HERA
The diffraction dissociation of virtual photons is considered in the
framework of conventional Regge theory. It is shown that the recent HERA data
on large rapidity gap events can be successfully described in terms of the
Pomeron structure function. Using Regge factorization, the latter can be
related to the deuteron structure function. The parameters which relate these
two structure functions are determined from soft hadronic diffraction data. The
size of the shadowing corrections at low x and large Q**2 is also obtained.Comment: 17 pages, TEX, preprint LPTHE Orsay 94-4
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
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
Absorption and J/psi Suppression in Heavy Ion Collisions
We discuss the J/psi suppression in the framework of multiple collision
models. From the analysis of the Pb-Pb NA50 data we conclude that the strength
of the absorption has increased, but we find no clear evidence for the
formation of the quark-gluon plasma.Comment: 8 pages, 4 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
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
Moment Analysis, Multiplicity Distributions and Correlations in High Energy Processes: Nucleus-Nucleus Collisions
Cumulant oscillations, or moment oscillations, appear if the KNO
multiparticle distribution decreases at large z, , faster than
the exponential, , with . In nucleus-nucleus
interactions this behaviour is related to the limitation in the average number
of elementary central collisions (or average number of strings centrally
produced), due to the finite number of nucleons involved. Colour deconfinement,
via percolating string fusion, will drastically decrease the fraction of
centrally produced strings and increase the cut-off parameter : Moment
oscillations will be displaced to smaller q and the width of the KNO
distribution and forward-backward particle correlations will become smaller.Comment: 11 pages, 2 Postscript figure
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