Subthreshold K+ production in deuteron and alpha induced nuclear reactions

Double differential cross sections have been measured for pi+ and K+ emitted around midraidity in d+A and He+A collisions at a beam kinetic energy of 1.15 GeV/nucleon. The total pi+ yield increases by a factor of about 2 when using an alpha projectile instead of a deuteron whereas the K+ yield increases by a factor of about 4. According to transport calculations, the K+ enhancement depends both on the number of hadron-hadron collisions and on the energy available in those collisions: their center-of-mass energy increases with increasing number of projectile nucleons

Bottomonium and Drell-Yan production in p-A collisions at the CERN SPS

In the past few years the NA50 experiment carried out a comprehensive study of heavy quarkonia production, both in proton-nucleus and nucleus-nucleus collisions. In particular, data from p-A collisions have been collected in order to estimate the size of the absorption of quarkonia states in cold nuclear matter. Along with the studies on J/psi and psi', NA50 measured for the first time Y production at 450 GeV incident energy ( sqrt(s)=29.1 GeV) on five 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 Y and Drell-Yan production. We analyzed as well the transverse momentum and rapidity distributions for the Y meson. The results are compared with previous measurements and with the predictions of theoretical models

Anomalous J/psi suppression in Pb-Pb interactions at 158 GeV/c per nucleon

The Drell-Yan and J/psi cross-sections measured in Pb-Pb collisions are compared with the values extrapolated from the results obtained in proton and light ion induced reactions. While the Drell-Yan production exhibits the normal expected behaviour, the yield of J/psi in Pb-Pb interactions is abnormally low, as it lies 9 standard deviations below the expected value. Moreover, the departure from the expected behaviour increases significantly from peripheral to central collisions. (C) 1997 Elsevier Science B.V

Anomalous J/psi suppression in Pb+Pb collisions at 158xA GeV/c.

Cross sections for J/psi' and Drell-Yan production in Pb+Pb collisions at 158xA GeV/c are presented and compared with results obtained by the NA38 and NA51 collaborations. The Pb+Pb data have been collected by the NA50 collaboration using the NA38 dimuon spectrometer. The Drell-Yan mechanism is found to scale as (A(projectile). B-target) in p+B-target and A(projectile)+B-target collisions including Pb+Pb collisions. Regarding J/psi, an anomalous suppression is observed in Pb+Pb collisions with respect to the suppression observed in p+B-target, O+B-target and S+U collisions. The cross section ratios psi'/(J/psi) are similar in Pb+Pb and S+U collisions

Intermediate mass muon pair continuum in Pb-Pb collisions at 158 GeV/c RID F-6345-2010 RID F-8827-2010

The NA50 experiment measures, at CERN SPS, the dimuon production in Pb-Pb collisions at 158 GeV/c incident momentum. In this paper an analysis of the intermediate mass region (1.5 less than or equal to M(mu mu)12.5 GeV/c(2)) is presented. Known dimuon sources in this interval of the spectrum are the e.m. annihilation of <q(q)over bar> pairs (i.e, Drell-Yan) and the semileptonic decay of charmed hadrons. The contribution of these processes is calculated by means of a fit to the measured invariant mass distribution (for Drell-Yan) and of a linear extrapolation of p-A experimental results obtained by NA38 (for charm). It will he shown that known sources do not account for all of the dimuon yield measured by NA50, i.e, an excess is observed. The size of the excess measured in Pb-Pb is larger than the one seen by NA38 in S-U collisions. The centrality dependence of this effect, both in S-U and Pb-Pb, is also discussed

Anomalous J/psi suppression in Pb+Pb collisions at 158xA GeV/c. RID F-6345-2010 RID F-8827-2010

Cross sections for J/psi<,psi>' and Drell-Yan production in Pb+Pb collisions at 158xA GeV/c are presented and compared with results obtained by the NA38 and NA51 collaborations. The Pb+Pb data have been collected by the NA50 collaboration using the NA38 dimuon spectrometer. The Drell-Yan mechanism is found to scale as (A(projectile). B-target) in p+B-target and A(projectile)+B-target collisions including Pb+Pb collisions. Regarding J/psi, an anomalous suppression is observed in Pb+Pb collisions with respect to the suppression observed in p+B-target, O+B-target and S+U collisions. The cross section ratios psi'/(J/psi) are similar in Pb+Pb and S+U collisions