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.

The ALICE dimuon trigger: overview and electronics prototypes

Presentation made at RPC99 and submitted to NIM ALICE is the LHC experiment (2005) dedicated to the study of heavy ion collisions. Amongst the ALICE sub-detectors, the muon spectrometer will investigate the dimuon production from heavy resonance (J/psi, Gamma) decays, which is believed to be a promising signature of the QGP (Quark Gluon Plasma) formation.For maximum efficiency of the spectrometer, a dedicated dimuon trigger is presently built. The detector partis itself based on RPCs operated in streamer mode and is the topic of another contribution to this conference. This paper gives the principle and the simulated performances of the trigger and is also focussed on the description of the electronics prototypes and future developments. The RPCs are read-out by X and Y orthogonal strips: the front-end chips are presently developed. The signals are sent to the trigger electronics which basically performs a pt cut on the tracks to reduce the background. A prototype of fast (decision time 200 ns) programmable electronics working in a pipelined mode at 40 MHz has been built and tested. This prototype handles simultaneously 160 digital information from the strips. The tests of the trigger card have required the construction of a pattern generator (160 bits at 40 MHz)

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