arXiv subjects

E. G. Ferreiro

Publications and source records attributed to E. G. Ferreiro.

At least 55 records · Page 3Linked to original sources

arXiv2012

J/ψ and ψ' production in proton(deuteron)-nucleus collisions: lessons from RHIC for the proton-lead LHC run

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 sqrt{s}=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.

hep-ph↗

arXiv2012

Ultra-relativistic heavy-ion physics with AFTER@LHC

We outline the opportunities for ultra-relativistic heavy-ion physics which are offered by a next generation and multi-purpose fixed-target experiment exploiting the proton and ion LHC beams extracted by a bent crystal.

nucl-ex↗

arXiv2012

A Fixed-Target ExpeRiment at the LHC (AFTER@LHC) : luminosities, target polarisation and a selection of physics studies

We report on a future multi-purpose fixed-target experiment with the proton or lead ion LHC beams extracted by a bent crystal. The multi-TeV LHC beams allow for the most energetic fixed-target experiments ever performed. Such an experiment, tentatively named AFTER for "A Fixed-Target ExperRiment", gives access to new domains of particle and nuclear physics complementing that of collider experiments, in particular at RHIC and at the EIC projects. The instantaneous luminosity at AFTER using typical targets surpasses that of RHIC by more than 3 orders of magnitude. Beam extraction by a bent crystal offers an ideal way to obtain a clean and very collimated high-energy beam, without decreasing the performance of the LHC. The fixed-target mode also has the advantage of allowing for spin measurements with a polarised target and for an access over the full backward rapidity domain up to xF ~ - 1. Here, we elaborate on the reachable luminosities, the target polarisation and a selection of measurements with hydrogen and deuterium targets.

hep-ex↗

arXiv2012

High multiplicity pp events and J/ψ production at LHC

We discuss the dependence of J/ψ production on the charged particle multiplicity in proton-proton collisions at LHC energies. We show that, in the framework of parton saturation or string interaction models, the hard J/ψ production exhibits a significant growth with the multiplicity, which is stronger than linear in the high density domain. This departure from linearity, that should affect any hard observable, applies for high multiplicity proton-proton collisions in the central rapidity region and is a consequence of the parton saturation or the strong interaction among colour ropes that take place at LHC energies. Our assumption, the existence of coherence effects present in proton-proton collisions at high energy, can also be checked by studying the particular shape of the probability distribution associated to the J/ψ production.

hep-ph↗

arXiv2012

Charged multiplicities in pp and AA collisions at LHC

The mid-rapidity charged particle multiplicities in pp and AA collisions at LHC energies are described in the framework of a generalized eikonal model with shadowing corrections incorporated in AA. We show that the pp data require a Pomeron intercept close to 1.2, higher than the conventional one close to 1.1. An $s^{0.11}$ energy dependence is obtained in the LHC range and beyond. The size and centrality dependence of the AA multiplicity at $\sqrt{s} = 2.76$ TeV is reproduced and its energy dependence is predicted.

hep-ph↗

arXiv2012

Centrality, rapidity, and transverse-momentum dependence of gluon shadowing and antishadowing on $J/ψ$ production in $d$Au collisions at $\sqrt{s}$=200 GeV

We have carried out a wide study of shadowing and antishadowing effects on \jpsi\ production in \dAu\ collisions at $\sqrt{s_{NN}}=200$ GeV. We have studied the effects of three different gluon nPDF sets, using the exact kinematics for a $2\to 2$ process, namely $g+g\to J/ψ+g$ as expected from LO pQCD. We have computed the rapidity dependence of \RCP\ and $R_{d\rm Au}$ 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 $2\to 1$ simplified kinematics. All these observables have been compared to the PHENIX data in \dAu\ collisions.

hep-ph↗

arXiv2011

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.

hep-ph↗

arXiv2011

Quarkonium production in high energy proton-proton and proton-nucleus collisions

We present a brief overview of the most relevant current issues related to quarkonium production in high energy proton-proton and proton-nucleus collisions along with some perspectives. After reviewing recent experimental and theoretical results on quarkonium production in pp and pA collisions, we discuss the emerging field of polarisation studies. Thereafter, we report on issues related to heavy-quark production, both in pp and pA collisions, complemented by AA collisions. To put the work in a broader perspective, we emphasize the need for new observables to investigate quarkonium production mechanisms and reiterate the qualities that make quarkonia a unique tool for many investigations in particle and nuclear physics.

hep-ph↗

arXiv2011

Cold Nuclear Matter Effects on extrinsic J/psi production at sqrt{s_{NN}}=2.76 TeV at the LHC

We evaluate the Cold Nuclear Matter effects on J/psi production in pPb and PbPb collisions at the current LHC energy, taking into account the gluon shadowing and the nuclear absorption. We use the complete kinematics in the underlying 2 to 2 partonic process, namely $g+g \to \jpsi + g$ as expected from LO pQCD. The resulting shadowing is responsible for a large J/psi suppression in pPb and PbPb, and shows a strong rapidity dependence.

hep-ph↗

arXiv2011

Cold Nuclear Matter Effects on jpsi Production with Extrinsic pT at $\sqrt{s_{NN}}=5.5\mathrm{~TeV}$ at the LHC

Taking into account the gluon shadowing and the $J/ψ$ nuclear absorption, we evaluate the Cold Nuclear Matter (CNM) effects on $J/ψ$ production in $p$Pb and PbPb collisions at the design LHC energy for PbPb collisions, $\sqrt{s_{NN}}=5.5$ TeV. In view of the good agreement between the yield prediction using the LO CSM and the ALICE data at 7 TeV, we employ the latter model to use a complete description of the kinematics of the underlying $2 \rightarrow 2$ partonic process, namely $g + g \rightarrow J/ψ+ g$. We observe a large $J/ψ$ suppression in $p$Pb and PbPb collisions due to the strong shadowing of the gluon distribution in the lead ion at the corresponding gluon momentum fractions. This suppression from CNM effects has a strong rapidity dependence which may compensate, partially or completely, that of of the predicted charm recombination in PbPb collisions.

hep-ph↗

arXiv2010

Centrality, Rapidity and Transverse-Momentum Dependence of Cold Nuclear Matter Effects on J/Psi Production in d+Au, Cu+Cu and Au+Au Collisions at sqrt(s_NN)=200 GeV

We have carried out a wide study of Cold Nuclear Matter (CNM) effects on J/Psi production in d+Au, Cu+Cu and Au+Au collisions at sqrt(s_NN)=200 GeV. We have studied the effects of three different gluon-shadowing parametrisations, using the usual simplified kinematics for which the momentum of the gluon recoiling against the J/Psi is neglected as well as an exact kinematics for a 2 -> 2 process, namely g+g -> J/psi+g as expected from LO pQCD. We have shown that the rapidity distribution of the nuclear modification factor R_dAu, and particularly its anti-shadowing peak, is systematically shifted toward larger rapidities in the 2 -> 2 kinematics, irrespective of which shadowing parametrisation is used. In turn, we have noted differences in the effective final-state nuclear absorption necessary to fit the PHENIX d+Au data. Taking advantage of our implementation of a 2 -> 2 kinematics, we have also computed the transverse momentum dependence of the latter nuclear modification factor, which cannot be predicted with the usual simplified kinematics. All the corresponding observables have been computed for Cu+Cu and Au+Au collisions and compared to the PHENIX and STAR data. Finally, we have extracted the effective nuclear absorption from the recent measurements of R_CP in d+Au by the PHENIX collaboration.

hep-ph↗

arXiv2010

On the theoretical and experimental uncertainties in the extraction of the J/psi absorption cross section in cold nuclear matter

We investigate the cold nuclear matter effects on $J/ψ$ production, whose understanding is fundamental to study the quark-gluon plasma. Two of these effects are of particular relevance: the shadowing of the parton distributions and the nuclear absorption of the $c\bar{c}$ pair. If $J/ψ$'s are not produced {\it via} a $2 \to 1$ process as suggested by recent theoretical works, one has to modify accordingly the way to compute the nuclear shadowing. This naturally induces differences in the absorption cross-section fit to the data. A careful analysis of these differences however requires taking into account the experimental uncertainties and their correlations, as done in this work for $d$Au collisions at $\sqrtsNN=200\mathrm{GeV}$, using several shadowing parametrisations.

hep-ph↗

arXiv2009

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.

hep-ph↗

arXiv2009

Cold Nuclear Matter effects on J/ψproduction at RHIC: comparing shadowing models

We present a wide study on the comparison of different shadowing models and their influence on \jpsi production. We have taken into account the possibility of different partonic processes for the $c \bar c$-pair production. We notice that the effect of shadowing corrections on \jpsi production clearly depends on the partonic process considered. Our results are compared to the available data on \dAu collisions at RHIC energies. We try different break up cross section for each of the studied shadowing models.

hep-ph↗

arXiv2009

Resolving the J/ψRHIC puzzles at LHC

Experiments with gold-gold collisions at RHIC have revealed (i) stronger suppression of charmonium production at forward rapidity than at midrapidity and (ii) the similarity between the suppression degrees at RHIC and SPS energies. To describe these findings we employ the model that includes nuclear shadowing effects, calculated within the Glauber-Gribov theory, rapidity-dependent absorptive mechanism, caused by energy-momentum conservation, and dissociation and recombination of the charmonium due to interaction with co-moving matter. The free parameters of the model are tuned and fixed by comparison with experimental data at lower energies. A good agreement with the RHIC results concerning the rapidity and centrality distributions is obtained for both heavy Au+Au and light Cu+Cu colliding system. For pA and A+A collisions at LHC the model predicts stronger suppression of the charmonium and bottomonium yields in stark contrast to thermal model predictions.

hep-ph↗

arXiv2008

Can the RHIC J/psi puzzle(s) be settled at LHC?

One observes strong suppression effects for hard probes, e.g. the production of J/psi or high-pT particles, in nucleus-nucleus (AA) collisions at RHIC. Surprisingly, the magnitude of the suppression is quite similar to that at SPS. In order to establish whether these features arise due to the presence of a thermalized system of quarks and gluons formed in the course of the collision, one should investigate the impact of suppression mechanisms which do not explicitly involve such a state. We calculate shadowing for gluons in the Glauber-Gribov theory and propose a model invoking a rapidity-dependent absorptive mechanism motivated by energy-momentum conservation effects. Furthermore, final state suppression due to interaction with co-moving matter (hadronic or pre-hadronic) has been shown to describe data at SPS. We extend this model by including the backward reaction channel, i.e. recombination of open charm, which is estimated directly from pp data at RHIC. Strong suppression of charmonium both in pA and AA collisions at LHC is predicted. This is in stark contrast with the predictions of models assuming QGP formation and thermalization of heavy quarks.

hep-ph↗

arXiv2008

Fluctuations and Transverse Momentum Distributions in the Color Clustering Approach

We present our results on transverse momentum fluctuations, multiplicity fluctuations and transverse momentum distributions for baryons and mesons in the framework of the clustering of color sources. We determine under what conditions the initial state configurations can lead to color connection, and more specifically, if variations of the initial state can lead to a transition from disconnected to connected color clusters, modifying the number of effective sources. We find that beyond a critical point, one has a condensate, containing interacting and hence color-connected sources. This point thus specifies the onset of color deconfinement. We show that the transverse momentum and multiplicity distributions are related to each other in a defined way. We obtain a non-monotonic dependence of the $p_T$ and multiplicity fluctuations with the number of participants. We present our results for the fluctuations and the transverse momentum distributions at RHIC energies compared to the existing experimental data and our predictions for LHC energies.

hep-ph↗

arXiv2008

Charmonium Dissociation and Recombination: Cold Effects

Thirty years ago, Matsui and Satz proposed the $J/ψ$ destruction as a signal of a Quark Gluon Plasma (QGP) formation, due to the Debye screening between the pair c-cbar. At the light of the recent experimental data, I review the different effects on $J/ψ$ production, from SPS to LHC energies, distinguishing between Cold Nuclear Matter (CNM) and QGP effects. Different possibilities and explanations for the available experimental data are discussed. Model predictions for the arriving LHC data are also presented.

hep-ph↗