A new measurement of J/psi suppression in Pb-Pb collisions at 158 GeV per nucleon

We present a new measurement of J/psi production in Pb-Pb collisions at 158 GeV/nucleon, from the data sample collected in year 2000 by the NA50 Collaboration, under improved experimental conditions with respect to previous years. With the target system placed in vacuum, the setup was better adapted to study, in particular, the most peripheral nuclear collisions with unprecedented accuracy. The analysis of this data sample shows that the (J/psi)/Drell-Yan cross-sections ratio measured in the most peripheral Pb-Pb interactions is in good agreement with the nuclear absorption pattern extrapolated from the studies of proton-nucleus collisions. Furthermore, this new measurement confirms our previous observation that the (J/psi)/Drell-Yan cross-sections ratio departs from the normal nuclear absorption pattern for semi-central Pb-Pb collisions and that this ratio persistently decreases up to the most central collisions.Comment: 19 pages, 10 figures. Submitted to Eur. Phys. J.

The onset of the anomalous J/ψ\psi suppression in Pb-Pb collisions at the CERN SPS

The $J/\psi$ suppression observed by the NA50 experiment is one of the most striking signatures for quark gluon plasma formation in Pb-Pb collisions at 158 AGeV. The $J/\psi$ production has been studied as a function of the centrality of the collision estimated via the forward energy EZDC released in a zero degree calorimeter (ZDC). The study of the correlation between the number of participant nucleons in the collisions, Npart, and EZDC allows to check whether the $J/\psi$ suppression pattern vs. EZDC is compatible with a sudden $J/\psi$ suppression mechanism expressed as a function of Npart

J/psi and psi' production and their normal nuclear absorption in proton-nucleus collisions at 400 GeV

We report a new measurement of J/psi, psi' and Drell-Yan cross-sections, in the kinematical domain $-0.425<y_{\rm cm}<0.575$ and $-0.5<\cos\theta_{\rm CS}<0.5$, performed at the CERN-SPS using 400 GeV/c incident protons on Be, Al, Cu, Ag, W and Pb targets. The dependence of the charmonia production cross-sections on the size of the target nucleus allows to quantify the so-called normal nuclear absorption. In the framework of the Glauber model, this new measurement is combined with results previously obtained with the same apparatus, under different experimental conditions, and leads to a precise determination of the J/psi and psi' absorption cross-sections in the surrounding nuclear matter.Comment: Accepted for publication in Euro. Phys. J.

Experimental hypersensitivity pneumonitis: influence of Th2 bias

Cultured murine CD4+ cells from Saccharopolyspora rectivirgula sensitized C3H/HeJ (Th1 bias) donors can adoptively transfer murine experimental hypersensitivity pneumonitis (EHP). We sensitized BALB/c mice (Th2 bias) with S. rectivirgula, obtained spleen and lung associated lymph node (LALN) cells, cultured the cells with specific antigen, and attempted adoptive transfer of EHP. We also treated both C3H/HeJ and BALB/c donor mice with IL4 and anti-IFNγ before exposure to S. rectivirgula and then cultured cells from both spleen and LALN before attempted transfer of EHP. We found that cultured spleen and lung associated lymph node cells can adoptively transfer EHP in both C3H/HeJ and BALB/c mice as demonstrated by infiltration of the recipient lungs with CD4+ lymphocytes. Treatment of both mouse strains with IL4 and anti-IFNγ did not change the ability of cultured cells to adoptively transfer EHP. We conclude that EHP induced by S. rectivirgula can occur in animals with either a Th1 or a Th2 bias and is not altered by treatment with IL4 and anti-IFNγ. This suggests that attributes of the antigen and not genetic background or cytokine environment at the site of initial sensitization determines the results of exposure to S. rectivirgula

ψ′\psi^{\prime} production in Pb-Pb collisions at 158 GeV/nucleon

$\psi{prime}$ production is studied in Pb-Pb collisions at 158 GeV/c per nucleon incident momentum. Absolute cross-sections are measured and production rates are investigated as a function of the centrality of the collision. The results are compared with those obtained for lighter colliding systems and also for the $J/\psi$ meson produced under identical conditions.psi' production is studied in Pb-Pb collisions at 158 GeV/c per nucleon incident momentum. Absolute cross-sections are measured and production rates are investigated as a function of the centrality of the collision. The results are compared with those obtained for lighter colliding systems and also for the J/psi meson produced under identical conditions

J/&#968; azimuthal anisotropy relative to the reaction plane in Pb-Pb collisions at 158 GeV per nucleon

Abstract: The J/psi azimuthal distribution relative to the reaction plane has been measured by the NA50 experiment in Pb-Pb collisions at 158 GeV/nucleon. Various physical mechanisms related to charmonium dissociation in the medium created in the heavy ion collision are expected to introduce an anisotropy in the azimuthal distribution of the observed J/psi mesons at SPS energies. Hence, the measurement of J/psi elliptic anisotropy, quantified by the Fourier coefficient v (2) of the J/psi azimuthal distribution relative to the reaction plane, is an important tool to constrain theoretical models aimed at explaining the anomalous J/psi suppression observed in Pb-Pb collisions. We present the measured J/psi yields in different bins of azimuthal angle relative to the reaction plane, as well as the resulting values of the Fourier coefficient v (2) as a function of the collision centrality and of the J/psi transverse momentum. The reaction plane has been estimated from the azimuthal distri..

Bottomonium and Drell–Yan production in p–A collisions at 450 GeV

AbstractThe NA50 Collaboration has measured heavy-quarkonium production in p–A collisions at 450 GeV incident energy (s=29.1 GeV). We report here results on the production of the ϒ states and of high-mass Drell–Yan muon pairs (mμμ>6 GeV/c2). The cross-section at midrapidity and the A-dependence of the measured yields are determined and compared with the results of other fixed-target experiments and with the available theoretical estimates. Finally, we also address some issues concerning the transverse momentum distributions of the measured dimuons

J/ψ\psi production and suppression at SPS energies

NA50We 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 $\sqrt{s}$=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 ($\sqrt{s}$=19.4 and $\sqrt{s}$=17.2 GeV} respectively). The p–A data allow us to determine with high accuracy the absorption cross section of the (pre-)resonant $c\bar{c}$ 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

Results on psi-prime production in nucleus-nucleus collisions at CERN-SPS

Abstract We report results on &#968;' production in Pb–Pb interactions at 158 GeV/c per nucleon incident momentum, from data collected by the NA50 experiment at CERN SPS. A comparison of proton- and sulfur-induced collisions shows a similar &#968;' production rate per nucleon–nucleon collision for S–U and Pb–Pb reactions, decreasing with increasing centrality and significantly lower than the rate measured from proton-induced reactions. This feature contrasts with J/&#968; production which exhibits a similar behaviour for reactions induced by protons and by sulfur nuclei and a significantly suppressed rate for Pb–Pb interactions