We review the context, the motivations and the expected performances of a comprehensive and ambitious fixed-target programme using the multi-TeV proton and ion LHC beams. We also provide a detailed ...account of the different possible technical implementations ranging from an internal wire target to a full dedicated beam line extracted with a bent crystal. The possibilities offered by the use of the ALICE and LHCb detectors in the fixed-target mode are also reviewed.
Cold nuclear matter effects on J/ψ production in proton–nucleus and nucleus–nucleus collisions are evaluated taking into account the specific J/ψ-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 cc¯-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 RAA in the forward rapidity region (with respect to the mid rapidity region) are partially explained, therefore potentially reducing the need for recombination effects.
We study the effect of nuclear matter in
ϒ
production in
d
Au collisions at RHIC and
p
Pb collisions at the LHC. We find that the nuclear modification factor,
, measured at RHIC is not satisfactorily ...reproduced by the conventional effects used in the literature, namely the modification of the gluon distribution in bound nucleons and an—effective—survival probability for a bound state to escape the nucleus. In particular, we argue that this probability should be close to 1 as opposed to the
J
/
ψ
case. We note that, at backward rapidities, the unexpected suppression of
observed by PHENIX hints at the presence of a gluon EMC effect, analogous to the quark EMC effect—but likely stronger. Further nuclear matter effects, such as saturation and fractional energy loss, are discussed, but none of them fit in a more global picture of quarkonium production. Predictions for
ϒ
(
nS
) for the forthcoming
p
Pb run at 5 TeV at the LHC are also presented.
Thanks to its multi-TeV LHC proton and lead beams, the LHC complex allows one to perform the most energetic fixed-target experiments ever and to study with high precision pp, pd and pA collisions at ...sNN=115GeV and Pbp and PbA collisions at sNN=72GeV. We present a selection of feasibility studies for the production of quarkonia, open heavy-flavor mesons as well as light-flavor hadrons in pA and PbA collisions using the LHCb and ALICE detectors in a fixed-target mode.
We report on the opportunities for spin physics and Transverse-Momentum Dependent distribution (TMD) studies at a future multi-purpose fixed-target experiment using the proton or lead ion LHC beams ...extracted by a bent crystal. The LHC multi-TeV beams allow for the most energetic fixed-target experiments ever performed, opening new domains of particle and nuclear physics and complementing that of collider physics, in particular that of RHIC and the EIC projects. The luminosity achievable with AFTER@LHC using typical targets would surpass that of RHIC by more that 3 orders of magnitude in a similar energy region. In unpolarised proton-proton collisions, AFTER@LHC allows for measurements of TMDs such as the Boer-Mulders quark distributions, the distribution of unpolarised and linearly polarised gluons in unpolarised protons. Using the polarisation of hydrogen and nuclear targets, one can measure transverse single-spin asymmetries of quark and gluon sensitive probes, such as, respectively, Drell-Yan pair and quarkonium production. The fixed-target mode has the advantage to allow for measurements in the target-rapidity region, namely at large x↑ in the polarised nucleon. Overall, this allows for an ambitious spin program which we outline here.
Transverse-momentum dependence of J/ψ shadowing effects Ferreiro, E. G.; Fleuret, F.; Rakotozafindrabe, A.
European physical journal. C, Particles and fields (Print),
06/2009, Letnik:
61, Številka:
4
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
We present a new approach to estimate the effect of gluon shadowing in nucleus + nucleus collisions and its consequences on the
J
/
ψ
production yield. Using kinematical information available from ...the measured
J
/
ψ
production in proton + proton collisions at
GeV, we build a Glauber Monte Carlo code which takes into account shadowing in two alternative ways: multiple-scattering corrections or
Q
2
evolution of parton densities. We exploit the dependence of these different parameterizations to the
J
/
ψ
transverse momentum and we give the first predictions on the resulting
p
T
dependence of the nuclear modification factor in deuteron + gold collisions at the same energy.
We study the impact of different cold nuclear matter effects both on J/ψ and ψ' production, among them the modification of the gluon distribution in bound nucleons, commonly known as gluon shadowing, ...and the survival probability for a bound state to escape the nucleus -the nuclear absorption. Less conventional effects such as saturation and fractional energy loss are also discussed. We pay a particular attention to the recent PHENIX preliminary data on ψ' production in dAu collisions at 200 GeV, which show a strong suppression for central collisions, 5 times larger than the one obtained for J/ψ production at the same energy. We conclude that none of the abovementioned mechanisms can explain this experimental result.
Résumé
Introduction
Les pathologies hépatiques dues à l’infection chronique par le virus de l’hépatite B (VHB) et de l’hépatite C sont devenues actuellement les premiers facteurs de comorbidité et de ...mortalité chez les patients infectés par le VIH (PVVIH). À Madagascar, aucune étude n’a été effectuée concernant ces co-infections. Ainsi, notre objectif était de déterminer la prévalence de la co-infection VIH/ VHB/VHC dans cinq centres hospitalo-universitaires malgaches, qui sont des centres de référence pour la prise en charge des PVVIH.
Méthodes
Il s’agissait d’une étude rétrospective, descriptive, transversale et multicentrique, durant la période du 2001 au 2011. La population d’étude comprenait des PVVIH appartenant aux files actives des cinq sites.
Résultats
Cent soixante patients étaient inclus. Le sex-ratio était de 0,92. L’âge moyen des PVVIH était de 33,42 ± 10 ans, avec des extrêmes de huit mois et de 60 ans. La prévalence globale des co-infections était de 7,5 %, dont 6,25 % pour le VIH/VHB et 1,25 % pour le VIH/VHC. On ne notait pas une co-infection VIH/VHB/VHC. La prévalence de la co-infection était similaire dans les deux genres. La majorité des co-infectés était célibataire,
n
= 8 (66,7 %). Deux sur trois des travailleurs de sexe avaient une co-infection.
Conclusion
La prévalence de la co-infection dans ces cinq centres de références était basse. Elle était probablement sous-estimée à cause de deux problèmes majeurs: le manque de moyen pour le dépistage, le nombre élevé de perdus de vue des PVVIH. Ainsi, un grand défi doit être relevé à tous les acteurs de santé à Madagascar pour remédier à ces fléaux.
Midrapidity production of π±, K±, and (¯p)p measured by the ALICE experiment at the CERN Large Hadron Collider, in Pb-Pb and inelastic pp collisions at √sNN=5.02 TeV, is presented. The invariant ...yields are measured over a wide transverse momentum (pT) range from hundreds of MeV/c up to 20 GeV/c. The results in Pb-Pb collisions are presented as a function of the collision centrality, in the range 0–90%. The comparison of the pT-integrated particle ratios, i.e., proton-to-pion (p/π) and kaon-to-pion (K/π) ratios, with similar measurements in Pb-Pb collisions at √sNN=2.76 TeV show no significant energy dependence. Blast-wave fits of the pT spectra indicate that in the most central collisions radial flow is slightly larger at 5.02 TeV with respect to 2.76 TeV. Particle ratios (p/π, K/π) as a function of pT show pronounced maxima at pT≈3GeV/c in central Pb-Pb collisions. At high pT, particle ratios at 5.02 TeV are similar to those measured in pp collisions at the same energy and in Pb-Pb collisions at √sNN=2.76 TeV. Using the pp reference spectra measured at the same collision energy of 5.02 TeV, the nuclear modification factors for the different particle species are derived. Within uncertainties, the nuclear modification factor is particle species independent for high pT and compatible with measurements at √sNN=2.76 TeV. The results are compared to state-of-the-art model calculations, which are found to describe the observed trends satisfactorily.
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