1,722,008 research outputs found
NA60 results on phi production in the hadronic and leptonic channels in In-In collisions at 158 GeV
No full textThe NA60 experiment at the CERN SPS studied phi meson production in In-In collisions at 158 A GeV via muon and kaon decay channels. Results in the hadronic channel are presented for the first time. These are discussed in the framework of the so-called phi puzzle through the comparison with the previous NA60 measurements in the muon channel. The yield and inverse m(T) slopes observed in the two channels are compatible within errors, showing that the large discrepancies seen in Pb-Pb collisions between NA50 (muon pairs) and NA49 (kaon pairs) are not seen in the NA60 In-In data
NA38/NA50 results on the low mass dimuon spectra
No full textThe dimuon mass spectrum produced in p-U collisions is well described, for masses below 1.5 GeV, as a superposition of light meson decays (the hadronic cocktail), the decays of charmed mesons and quark-antiquark annihilation into muon pairs. When these results are extrapolated to sulphur induced collisions, a small excess is observed over the whole mass region, particularly pronounced in the phi peak
ϕ production at forward rapidity in pp, p–Pb and Pb–Pb collisions with ALICE
No full textThe ALICE experiment at the LHC measured vector meson production in p-Pb collisions at sNN=5.02 TeV , pp and Pb-Pb collisions at sNN=2.76 TeV . In pp collisions, the ϕ differential cross section as a function of p T was measured in the range 1<pT<5 GeV/c and compared with the calculations from PHOJET and PYTHIA. In p-Pb collisions, measurements of the ϕ yield and the nuclear modification factor in the rapidity ranges 2.03<y<3.53 (p-going direction) and −4.46<y<−2.96 (Pb-going direction) are shown. An asymmetry between the cross section at forward and backward rapidity is observed. Results are compared with the predictions provided by commonly used event generators. In Pb-Pb collisions, the ϕ yield and the nuclear modification factor are obtained as a function of centrality in the intermediate p T region (2<pT<5 GeV/c) and for 2.5<y<4 . Differences are observed between these results and those measured in the same p T range at midrapidity in the KK channel
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 similar to 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
Dimuon enhancement in nucleus-nucleus ultrarelativistic interactions
No full textThe study of muon pairs in the mass region 1.5 < M-mu mu < 2.5 GeV/c(2) in 450 GeV/c p-A, 200 GeV/nucleon S-U and 158 GeV/nucleon Pb-Pb collisions is presented. In p-A interactions. the dimuon signal mass spectra are well described by a superposition of Drell-Yan and charmed meson semi-leptonic decay contributions, in agreement with previous experiments when considering a linear A dependence. In nucleus-nucleus reactions, taking only into account these two physical ingredients, a dimuon enhancement both with increasing A.B and centrality is observed
Charmonium production in Pb-Pb interactions at 158 GeV/c per nucleon
No full textThe NA50 collaboration has measured J/psi, psi' and Drell-Yan pair production in Pb-Pb interactions at 158 GeV/c per nucleon at the CERN SPS. Final results from the 1995 run and preliminary ones from the higher statistics 1996 run are presented. An anomalous J/psi suppression (relative to the Drell-Yan process) has been observed with respect to the suppression pattern established in experiments NA38 and NA51 with proton, oxygen and sulfur beams. The 1996 data allow a detailed study of the suppression pattern in the Pb-Pb sample itself, showing a discontinuity around an E-T value (the neutral transverse electromagnetic energy) of 50 GeV. The psi' is also suppressed relative to Drell-Yan, with a pattern very similar to the one observed in S-U collisions. Finally, the pr distributions of dimuons are presented. The average p(T)(2) of the J/psi in Pb-Pb collisions does not increase any more with E-T above 100 GeV
phi, rho and omega production in Pb-Pb collisions at 158 GeV/c(2) per nucleon
No full textThe production of low mass dimuons has been measured in Pb-Pb collisions at the SPS (CERN). (phi/(rho+omega)) ratios have been studied with respect to the centrality of the collision. Preliminary results on phi and (rho+omega) multiplicities as a function of the number of participants are presented. Values for the temperature T are deduced from the cross sections studies in the limited transverse mass M-t domain covered by the experimental apparatus
phi, rho and omega production in collisions induced by deuteron and heavy ions around 200 GeV per nucleon
No full textThe production of low mass dimuons has been measured in d-C, d-U and S-U collisions at 200 GeV per nucleon, and in Pb-Pb collisions at 158 GeV per nucleon. phi/(omega + rho) ratio and phi and omega + rho cross sections are studied showing phi increase relatively to the omega + rho, with increasing size of the system or centrality, and cross sections increase rates which are different in ion and deuteron induced reactions
Enhancement of intermediate mass dimuons in nucleus-nucleus collisions at the CERN-SPS
No full textDimuon production in p-A, S-U and Pb-Pb collisions at the CERN-SPS has been studied by the NA38/NA50 collaboration. A 4-D unfolding method has been applied to the data to study the intermediate mass region (IMR) between 1.6 and 2.5 GeV/c(2). The superposition of conventional processes, namely Drell-Yan and open charm, extrapolated from p-A distributions is unable to describe the overproduction observed in the ion data. Medium effects or D-meson rescattering cannot account for the experimental results. Two possible explanations of the observed excess, namely an enhancement of charm production or the presence of thermal dilepton radiation, are also discussed
Latest results from NA50 on J/psi suppression in Pb-Pb collisions
No full textThe main goal of the NA50 experiment is to study the J/psi suppression pattern in PL-rb interactions, at 158 GeV/c per nucleon at the CERN SPS. We present here the results from the 1996 (final) and 1908 (preliminary) data taking periods. They confirm and extend our previous observation that the J/psi is anomalously supressed from peripheral to central collisions. With new event selection procedures and different analysis techniques, we observe that in peripheral collisions the J/psi cross section per nucleon-nucleon collision agrees with the pattern inferred from a wide range of measurements with lighter systems, from pp up to S-U. When the collisions become more central a clear departure from this behaviour is observed. The 1996 data show a sudden drop in the J/psi production yield for E-T values above 40 GeV, where E-T is the neutral transverse electromagnetic energy released in the colision and measured in the EM calorimeter. The 1998 data provide a big improvement in the study of the most central region, where a second change in the pattern becomes visible
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