246 research outputs found
The NA60 silicon pixel telescope
No full textThe NA60 experiment studies the production of open charm and prompt dimuons in proton-nucleus and nucleus-nucleus collisions at the CERN SPS. The main goal of NA60 is the study of various possible signatures of the transition from hadronic to deconfined partonic matter, e.g. anomalous charmonium suppression, dimuons from thermal radiation and modifications of vector meson properties. Reaching these goals is facilitated by the use of new state-of-the-art silicon detectors in the vertex region. Downstream of the target and inside a 2.5T dipole magnetic field a pixel telescope measures the charged tracks originating from the collisions. The full pixel telescope consists of 16 planes with 96 ALICEILHCb pixel detector assemblies in total. This paper describes the setup of the pixel telescope, results from tests as well as the expected implications of the operation of the silicon detectors in the harsh radiation environment of the NA60 experiment, with heavy-ion collisions. (c) 2005 Elsevier B.V. All rights reserved. RI Tinoco Mendes, Andre David/D-4314-2011; Cortese, Pietro/G-6754-201
Low mass dimuon production in proton-nucleus collisions with the NA60 apparatus
No full textDuring the June 2002 run NA60 collected around 600 000 dimuon triggers in proton-nucleus collisions at 400 GeV. We show that the collected dimuon mass spectra can be understood in terms of known sources. The specific target setup, consisting of Beryllium, Indium and Lead targets, simultaneously exposed to the beam, allowed us to study the nuclear dependence of the production cross-section of the omega and phi resonances. The elementary nucleon-nucleon production cross-sections at 400 GeV for the rho, omega and phi mesons are also presented. By using the eta-Dalitz decay, dominating the mass range below 450 MeV, we, furthermore, extracted the eta production cross-section and its nuclear dependence. The results are discussed in the framework of previous measurements, mostly obtained in different decay channels, performed by NA27, HELIOS-1 and CERES-TAPS
Low mass dimuon production in indium-indium collisions at 158 A GeV
No full textThe NA60 experiment studies open charm and prompt dimuon production in proton-nucleus and nucleus-nucleus collisions at the CERN SPS. During 2003 the experiment collected data in Indium-Indium collisions at 158 GeV per nucleon. Almost 240 million dimuon events were recorded. New results on J/psi. suppression, open-charm production and low mass dimuons should help clarify some interesting questions left open by previous experiments. After a brief detector description, this paper focuses on the analysis of the low mass dimuons. Preliminary results are presented on the phi/psi. production cross section ratios and on the phi transverse momentum distributions, both as a function of collision centrality. RI Tinoco Mendes, Andre David/D-4314-2011; Cortese, Pietro/G-6754-201
A first look at open charm production in Indium-Indium collisions at SPS energies
No full textNA60 is an experiment at the CERN-SPS devoted to the study of dimuon production in heavy-ion and proton-nucleus collisions. The main topics under study are low mass vector meson production, J/psi production and suppression, and the sources of the dimuon continuum in the mass range 1.2 - 2.7 GeV/c(2). In 2003, NA60 collected similar to 230 million dimuon events from Indium-Indium collisions. We present preliminary results of the analysis of this data sample in view of measuring the open charm contribution to the dimuon spectrum. Although we are still working on the final background subtraction procedure, we can already demonstrate that the detector performance is good enough to allow the separation of prompt dimuons from muon pairs originating in distant D (D) over bar decays
Dimuon and charm production in In+In collisions at the CERN SPS
No full textThe NA60 experiment studies muon pair production with proton and Indium beams. It is a second generation experiment, designed to answer specific questions left open, in the leptonic sector, by the previous round of SPS experiments, finished in 2000. The results presented in this paper cover the dimuon invariant mass range from the threshold to the J/psi. The main physics topics that we address include the in-medium modifications of the rho meson, the origin of the dimuon excess observed between the phi and the J/psi, and the study of the anomalous J/psi suppression. For each of these subjects, the NA60 results represent a significant step forward towards a deeper understanding of the physics of heavy ion collisions at SPS energies. RI Tinoco Mendes, Andre David/D-4314-2011; Cortese, Pietro/G-6754-201
Anomalous J/psi suppression in In-In collisions at 158 GeV/nucleon
No full textJ/psi suppression has been studied by the NA60 experiment in Indium-Indium collisions. A new analysis technique, based only on the J/psi sample, allows to accurately study the centrality dependence of J/psi production. The observed pattern indicates that a suppression is already present in In-In collisions, setting in at similar to 90 participant nucleons. A comparison with the available theoretical models is also presented
J/psi production in Indium-Indium collisions
No full textThe study of dilepton production in heavy-ion collisions at the CERN SPS provided some of the most interesting observations done so far in the search for the quark gluon plasma. However, several aspects of the understanding of these measurements need to be clarified. For example, the study of the J/psi production in different colliding systems should help to disentangle which is the variable driving the J/psi suppression. The NA60 experiment, with a new radiation tolerant Silicon pixel detector, studied Indium-Indium interactions in the year 2003. In this paper, we present the J/psi DY ratio, integrated over all the centralities of the collisions, together with a first study of the J/psi transverse momentum and polarization. RI Tinoco Mendes, Andre David/D-4314-2011; Cortese, Pietro/G-6754-201
Phi meson production in NA60
No full textNA60 is a fixed-target experiment at the CERN SPS which measured dimuon production in nucleus-nucleus and proton-nucleus collisions. The experiment collected muon pair samples of unprecedented quality in heavy-ion experiments. This paper presents a high quality measurement of the p(T) distribution of the phi meson, covering a broad p(T) window. The data were collected in 2003 in In-In collisions at 158 GeV per nucleon. The results, presented as a function of centrality, were studied against several possible sources of systematic effects and proved to be fairly stable. We show that the inverse m(T) slope measured in In-In collisions, in the phi -> mu mu decay channel, depends significantly on the range used to perform the fit. When the fit is performed at low transverse momentum, the effective inverse slope increases from peripheral to central collisions, as measured by other experiments. We finally show that our measurement for In-In is compatible with the overall systematics of T slope versus mass, measured in different collision systems by the NA49 experiment. RI Tinoco Mendes, Andre David/D-4314-2011; Cortese, Pietro/G-6754-201
J/psi production in indium-indium collisions at 158 GeV/Nucleon
No full textThe NA60 experiment studies muon pair production at the CERN Super Proton Synchrotron. In this Letter we report on a precision measurement of J/psi in In-In collisions. We have studied the J/psi centrality distribution, and we have compared it with the one expected if absorption in cold nuclear matter were the only active suppression mechanism. For collisions involving more than similar to 80 participant nucleons, we find that an extra suppression is present. This result is in qualitative agreement with previous Pb-Pb measurements by the NA50 experiment, but no theoretical explanation is presently able to coherently describe both results
Phi production in p-A and In-In collisions
No full textThe NA60 experiment studied Phi meson production in p-A and In-In collisions at the CERN SPS. The ratio Phi / Omega shows an increase by a factor ?2 from peripheral to central collisions. The inverse slope parameter T of the p T spectrum increases with centrality, and seems to agree with the previous NA49 measurements. ? 2006
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