220 research outputs found
Color strings, pomeron shadowing and Color Glass Condensate
I review the problem of parton saturation and its implications through three
in principal different approaches, but somewhat related: saturation in a
geometrical approach, QCD saturation through the Color Glass Condensate and
shadowing in a Pomeron approach.Comment: 8 pages, 3 figures, Fifth International Conference on Perspectives in
Hadronic Physics 22-26 May 2006 Trieste, Ital
Aspects of the unitarized soft multipomeron approach in DIS and diffraction
We studyin detail the main features of the unitarized Regge model (CFKS), recentlyprop osed to describe the small-Q2 domain. It takes into account a two-component description with two types of unitarized contributions: one is the multiple pomeron exchange contribution, interacting with the large dipole size configurations, and the other one consists of a unitarized dipole cross section, describing the interaction with the small size dipoles. We analyze the ratio between soft and hard pieces as a function of the virtuality, and also compare the resulting dipole cross section to that from the saturation model. Diffraction dissociation is also considered, showing the scaling violations in diffractive DIS and estimating the corresponding logarithmic slope
Quarkonium as a tool: cold nuclear matter effects
We discuss the quarkonium production as a tool for the study of the Quark
Gluon Plasma. In particular, we concentrate on the Cold Nuclear Matter effetcs.
We show that quarkonium production is also useful for the study of Quantum
Chromodynamics first principles and the nuclear Parton Distribution Functions.Comment: Contribution to the proceedings of QUARKONIUM 2010: Three Days Of
Quarkonium Production in pp and pA Collisions, 29-31 July 2010, Palaiseau,
France. 4 pages, 4 figure
On the jet spectrum in nucleus-nucleus interactions
We derive the inclusive transverse spectrum of minijets in nuclear collisions
at very high energies by assuming that the nuclear S-matrix factorizes into a
product of elastic S-matrices for elementary partonic collisions. Interference
effects and, in particular, the contribution of loop diagrams are fully taken
into account in the derivation of the spectrum, which is shown to coincide with
the result earlier obtained by superposing the elementary interactions
incoherently. A quantitative analysis confirms that the deformation induced by
multiple collsions is a large effect at RHIC and LHC energies, for transverse
momenta ~ 20 GeV.Comment: text in LaTex, 4 figures in P
Centrality, rapidity, and transverse-momentum dependence of gluon shadowing and antishadowing on production in Au collisions at =200 GeV
We have carried out a wide study of shadowing and antishadowing effects on
\jpsi\ production in \dAu\ collisions at GeV. We have
studied the effects of three different gluon nPDF sets, using the exact
kinematics for a process, namely as expected from LO
pQCD. We have computed the rapidity dependence of \RCP\ and for
the different centrality classes of the PHENIX data. For mid rapidities, we
have also computed the transverse-momentum dependence of the nuclear
modification factor, which cannot be predicted with the usual
simplified kinematics. All these observables have been compared to the PHENIX
data in \dAu\ collisions.Comment: 10 pages, 11 figures, talk given by N. Matagne at the conference
"thirty years of hadronic physics", Spa, Belgium, April 6-8, 2011, to appear
in Few Body System
Universal behavior of baryons and mesons' transverse momentum distributions in the framework of percolation of strings
In the framework of percolation of strings, we present predictions for the
and for mesons and baryons and for ratios
at LHC energies.Comment: Presented at "Heavy Ion Collisions at the LHC: last call for
predictions", Geneva Switzerland, May 14th-June 8t
Cold nuclear matter effects on J/psi production: intrinsic and extrinsic transverse momentum effects
Cold nuclear matter effects on J/psi production in proton-nucleus and
nucleus-nucleus collisions are evaluated taking into account the specific J/psi
production kinematics at the partonic level, the shadowing of the initial
parton distributions and the absorption in the nuclear matter. We consider two
different parton processes for the c-cbar pair production: one with collinear
gluons and a recoiling gluon in the final state and the other with initial
gluons carrying intrinsic transverse momentum. Our results are compared to RHIC
observables. The smaller values of the nuclear modification factor R_AA in the
forward rapidity region (with respect to the mid rapidity region) are partially
explained, therefore potentially reducing the need for recombination effects.Comment: 7 pages, 11 figures, LaTeX, uses elsarticle.cls (included).v2:
version (with minor text revisions and Fig 2 and 4a modified) to appear in
Phys.Lett.
Baryon and Antibaryon Production in Hadronic and Nuclear Interactions
We introduce a new formulation of the diquark breaking mechanism which
describes with no free parameters the huge nuclear stopping observed in central
nucleus-nucleus collisions. Supplemented, in the dual parton model, with
strings originating from diquark--antidiquark pairs from the nucleon sea, it
gives a substantial increase of hyperon and antihyperon yields from to
central collisions. Compared to data, this increase is slightly
underestimated for 's and 's but is five times too small for
's. Introducing final state interactions, a reasonable description of
all baryon and antibaryon yields is achieved.Comment: 17 pages, 4 postscript figure
Heavy-ion Physics at a Fixed-Target Experiment Using the LHC Proton and Lead Beams (AFTER@LHC): Feasibility Studies for Quarkonium and Drell-Yan Production
We outline the case for heavy-ion-physics studies using the multi-TeV lead LHC beams in the fixed-target mode. After a brief contextual reminder, we detail the possible contributions of AFTER@LHC to heavy-ion physics with a specific emphasis on quarkonia. We then present performance simulations for a selection of observables. These show that , and production in heavy-ion collisions can be studied in new energy and rapidity domains with the LHCb and ALICE detectors. We also discuss the relevance to analyse the Drell–Yan pair production in asymmetric nucleus–nucleus collisions to study the factorisation of the nuclear modification of partonic densities and of further quarkonium states to restore their status of golden probes of the quark–gluon plasma formation.Peer Reviewe
Schwinger Model and String Percolation in Hadron-Hadron and Heavy Ion Collisions
In the framework of the Schwinger Model for percolating strings we establish
a general relation between multiplicity and transverse momentum square
distributions in hadron-hadron and heavy ion collisions. Some of our results
agree with the Colour Glass Condensate model.Comment: 7 pages, 1 figur
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