The ALICE muon spectrometer and related physics

ALICE, présenté par P. DupieuxThe LHC heavy ion physics program aims at investigating the properties of strongly interacting matter at extreme energy density where the formation of the Quark Gluon Plasma is expected. Among the most promising observables, open heavy flavours and heavy quarkonium states are especially relevant since, on the one hand, they are copiously produced and, on the other hand, they provide sensitive information on the collision at both short timescale (production mechanisms) and long timescale (medium effects). In ALICE, they will be measured through the hadronic channel as well as from (di)electrons and (di)muons. Particular emphasis will be put here on their measurement in the (di)muon decay channel. The ALICE muon spectrometer will be described as well as its construction and installation status. A few selected topics concerning muon physics in heavy ion collisions at LHC will be addressed and the expected performances of the ALICE muon spectrometer will be shown

Physics perspectives with the ALICE muon spectrometer

présenté par P. Dupieux, paru dans le supplément du journalALICE (A Large Ion Collider Experiment) will be the detector dedicated to the study of nucleus nucleus collisions at the LHC. The muon spectrometer of ALICE is dedicated to the measurement of heavy flavors in the muon channel. A brief description of the ALICE muon spectrometer and its physics program is reported. The expected performances for open and hidden charm and bottom measurements are presente

The Dimuon Trigger of the ALICE - LHC Experiment

We describe the trigger system of the ALICE dimuon spectrometer, based on RPC detectors. The background rate is at least one order of magnitude less in ALICE than in LHC p-p experiments due to the lower luminosity in ion running. Hence we study the possibility to operate the RPCs either in streamer or proportional mode. We report a study done with cosmic rays concerning gas mixtures for streamer mode. The aim is to minimise the streamer charge for a better flux capability of the RPC and a smaller cluster size, as needed for ALICE. We also give the results of a beam test at SPS where the RPC was placed in the vicinity of a hadron absorber, simulating the operation conditions in ALICE

The Local Trigger Electronics of the ALICE dimuon trigger

This document has been prepared for the Production Readiness Review of the Local trigger electronics of the ALICE dimuon arm, LHCC milestones n°429. It describes the design and the performances of a prototype board, developed at the LPC Clermont-Ferrand, in VME 9U format and based on programmable circuits

Abundance of Delta Resonances in 58Ni+58Ni Collisions between 1 and 2 AGeV

Charged pion spectra measured in 58Ni-58Ni collisions at 1.06, 1.45 and 1.93 AGeV are interpreted in terms of a thermal model including the decay of Delta resonances. The transverse momentum spectra of pions are well reproduced by adding the pions originating from the Delta-resonance decay to the component of thermal pions, deduced from the high transverse momentum part of the pion spectra. About 10 and 18% of the nucleons are excited to Delta states at freeze-out for beam energies of 1 and 2 AGeV, respectively.Comment: 14 pages, LaTeX with 3 included figures; submitted to Physics Letters

Two-proton small-angle correlations in central heavy-ion collisions: a beam-energy and system-size dependent study

Small-angle correlations of pairs of protons emitted in central collisions of Ca + Ca, Ru + Ru and Au + Au at beam energies from 400 to 1500 MeV per nucleon are investigated with the FOPI detector system at SIS/GSI Darmstadt. Dependences on system size and beam energy are presented which extend the experimental data basis of pp correlations in the SIS energy range substantially. The size of the proton-emitting source is estimated by comparing the experimental data with the output of a final-state interaction model which utilizes either static Gaussian sources or the one-body phase-space distribution of protons provided by the BUU transport approach. The trends in the experimental data, i.e. system-size and beam energy dependences, are well reproduced by this hybrid model. However, the pp correlation function is found rather insensitive to the stiffness of the equation of state entering the transport model calculations.Comment: 9 pages, 8 figures, accepted at Eur. Phys. Journ.

Measurement of K∗(892)0K^*(892)^0 and K0K^0 mesons in Al+Al collisions at 1.9AA GeV

New measurement of sub-threshold $K^*(892)^0$ and $K^0$ production is presented. The experimental data complete the measurement of strange particles produced in Al+Al collisions at 1.9$A$ GeV measured with the FOPI detector at SIS/GSI. The $K^*(892)^0$ / $K^0$ yield ratio is found to be $0.0315\pm 0.006 (\mathrm{stat.})\pm 0.012 (\mathrm{syst.})$ and is in good agreement with the UrQMD model prediction. These measurements provide information on in-medium cross section of $K^+$ - $\pi^-$ fusion which is the dominant process on sub-threshold $K^*(892)^0$ production.Comment: 5 pages, 4 figures, accepted for publication in Phys. Rev.

Strange meson production in Al+Al collisions at 1.9A GeV

The production of K$^+$, K$^-$ and $\varphi$(1020) mesons is studied in Al+Al collisions at a beam energy of 1.9A GeV which is close or below the production threshold in NN reactions. Inverse slopes, anisotropy parameters, and total emission yields of K$^{\pm}$ mesons are obtained. A comparison of the ratio of kinetic energy distributions of K$^-$ and K$^+$ mesons to the HSD transport model calculations suggests that the inclusion of the in-medium modifications of kaon properties is necessary to reproduce the ratio. The inverse slope and total yield of $\phi$ mesons are deduced. The contribution to K$^-$ production from $\phi$ meson decays is found to be [17 $\pm$ 3 (stat) $^{+2}_{-7}$ (syst)] %. The results are in line with previous K$^{\pm}$ and $\phi$ data obtained for different colliding systems at similar incident beam energies.Comment: 16 pages, 11 figure