1,721,637 research outputs found
J/psi production and suppression at SPS energies
No full textWe present the set of measurements carried out by the NA50 experiment to study J/psi production in proton- and ion-induced reactions. We also make use of results obtained previously under similar conditions by experiments NA51, NA38 and NA3. All these measurements were performed in fixed target experiments at the CERN SPS. Due to accelerator constraints, momentum was 450, 400 and 200 GeV/c for incident proton beams (corresponding to root s- = 29.0, 27.4, 19.4 GeV respectively) whereas, for ion beams, incident momentum was 200 GeV/nucleon for oxygen and sulfur and 158 GeV/nucleon for Pb beams (root s = 19.4 and root s- = 17.2 GeV respectively). The p-A data allow us to determine with high accuracy the absorption cross section of the (pre-)resonant c state with nuclear matter. The J/psi production cross section normally expected for ion-induced reactions can then be determined and compared to the results obtained from the data collected for oxygen- and sulfur-induced collisions. Finally, we also present the most recent results on J/psi production in Pb-Pb interactions. They are based on the last data sample collected with an improved experimental set-up and are compared with the expectations inferred from similar measurements on lighter nuclei collisions
Charmonium and open-charm production in proton-nucleus collisions at the CERN SPS
No full textp-A collisions provide an essential reference for the study of J/psi suppression in heavy-ion interactions since they allow us to evaluate cold nuclear matter (CNM) effects. These include initial state effects, such as shadowing and parton energy loss, and final state effects such as J/psi breakup in the collisions with nucleons. To evaluate these effects, NA60 has measured J/psi production in p-A collisions with seven nuclear targets at root s = 27.4 GeV and, for the first time, at the same root s of Pb-Pb and In-In SPS data: 17.3 GeV. More recently, open-charm production has also been studied by analysing the dimuon continuum generated by the simultaneous semi-muonic decay of D meson pairs. The comparison of the production of closed charm with its natural reference (open charm) can give some insight on how the interplay of the different CNM effects produces the observed (effective) J/psi suppression
and Drell-Yan production in p-A collisions at 450 GeV incident energy
No full textIn the past few years the NA50 experiment carried out a comprehensi v e study of heavy quarkonia production, both in proton-nucleus and nucleus-nucleus collisions. In particular , data from p-A collisions hav e been collected in order to estimate the size of the absorption of quarkonia states in cold nuclear matter . Along with the studies on J/ ψ and ψ , NA50 measured for the first time ϒ production at 450 GeV incident energy ( s 29 1 GeV) on fi v e nuclear targets (Be, Al, Cu, Ag and W) in the dimuon decay channel. We report here results on the cross section at mid-rapidity and the nuclear dependence of ϒ and Drell-Yan production. We analyzed as well the transverse momentum and rapidity distributions for the ϒ meson. The results are compared with previous measurements and with the predictions of theoretical models
Pb-Pb Collisions at the SPS: from Hadronic to Deconfined Matter
No full textIn this paper, some of the recent experimental results from Pb-Pb collisions at the SPS will be reviewed. First, the experimental observables connected with the geometry of the collisions will be described. Then the different signatures related to the phase transition to a Quark-Gluon Plasm (QGP) will be presented. The various experiments provide a detailed picture of heavy ion collisions at the SPS energies. The results can be coherently interpreted in a scenario where, at least in central Pb-Pb collisions, a transition from hadronic to deconfined matter occurs
Latest results from NA60
No full textNA60 is a fixed target experiment at the CERN SPS studying dimuon production in different colliding systems: In-In at 158 A GeV incident energy and p-A collisions at 158 and 400 GeV. A strong excess of dimuon pairs has been observed in the region of the invariant mass spectrum below the J/ψ. The high resolution of the NA60 detector allowed to measure the in-medium modifications of the ρ spectral function and to clarify the origin of the dimuon excess in the region above the . The J/ψ suppression has been studied in In-In and p-A collisions at 158 GeV incident energy. The latest results on these topics are addressed in this paper
NA60 results on Quarkonia
No full textThe NA60 experiment at CERN SPS has performed a study of J/Psi production in p-A collisions at 158 GeV incident energy. For the first time it has been possible to study cold-nuclear matter effects at the same energy as In-In and Pb-Pb collisions, where an "anomalous J/Psi suppression" had been observed. We present preliminary results on the J/Psi absorption cross section at 158 GeV and compare them with a "reference measurement" taken with the same apparatus at 400 GeV and with other results available in the literature
J/Psi, Psi' and DY production in proton nucleus collisions at 450 GeV incident energy at the NA50 experiment
No full textDrell-Yan, and production in proton-induced collisions on Be, Al, Cu, Ag and W targets has been studied by the NA50 collaboration at the CERN SPS. The results are needed to fully understand nuclear suppression of the charmonia states and to provide a solid and accurate reference for the study of the anomalous
suppression, observed by NA50 in Pb-Pb collisions. We show that
suppression in proton-nucleus and in Sulfur-Uranium collisions can be understood in terms of nuclear absorption and there is no indication of an additional mechanism in S-U compared to p-A collisions
Role of parton shadowing in the comparison of p-A and A-A results on J/psi suppression at energies available at the CERN Super Proton Synchrotron
No full textThe observation of an anomalous J/psi suppression in nucleus-nucleus collisions is one of the most important results of the Super Proton Synchrotron (SPS) heavy-ion program. An essential ingredient in this result is the determination, obtained by studying p-A collisions, of effects not related with the formation of a deconfined medium. These effects are extrapolated to A-Acollisions, determining a reference J/psi yield that is then compared with the measurements. In this article we investigate the role of parton shadowing on the determination of such a reference, and we calculate its effect for In-In and Pb-Pb collisions as a function of rapidity and centrality
Recent results from the CERN NA60 experiment
No full textNA60 is a CERN SPS experiment that studied dimuon production in In-In collisions at 158 A·GeV
per nucleon. More recently proton nucleus collisions have also been investigated in order to provide a reference for heavy ion studies. Some of the most important results obtained by the experiment are the first measurement of the rho spectral function in nuclear collision and the study
of its medium-induced modifications, the production of thermal muon pairs in the invariant mass region between the phi and the J/psi, and the study of the J/psi suppression. Recent results include further studies on the characterization of thermal pairs, the comparison of phi production in μμ
and KK channels (the phi puzzle) and the first measurement of cold nuclear matter effects on J/psi
production at 158 GeV, the same energy where the anomalous J/psi suppression has been observed
Charged-particle multiplicity density at mid-rapidity in central Pb-Pb collisions at sqrt(s_NN) = 2.76 TeV
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