RPC with low-resistive phosphate glass electrodes as a candidate for the CBM TOF

Usage of electrodes made of glass with low bulk resistivity seems to be a promising way to adapt the Resistive Plate Chambers (RPC) to the high-rate environment of the upcoming CBM experiment. A pilot four-gap RPC sample with electrodes made of phosphate glass, which has bulk resistivity in the order of 10^10 Ohm cm, has been studied with MIP beam for TOF applications. The tests have yielded satisfactory results: the efficiency remains above 95% and the time resolution stays within 120 ps up to the particle rate of 18 kHz/cm2. The increase in rate from 2.25 to 18 kHz/cm2 leads to an increase of estimated "tails" fraction in the time spectrum from 1.5% to 4%.Comment: 8 pages, 6 figures, submitted to Elsevier Scienc

Alignment of the ALICE Inner Tracking System with cosmic-ray tracks

37 pages, 15 figures, revised version, accepted by JINSTALICE (A Large Ion Collider Experiment) is the LHC (Large Hadron Collider) experiment devoted to investigating the strongly interacting matter created in nucleus-nucleus collisions at the LHC energies. The ALICE ITS, Inner Tracking System, consists of six cylindrical layers of silicon detectors with three different technologies; in the outward direction: two layers of pixel detectors, two layers each of drift, and strip detectors. The number of parameters to be determined in the spatial alignment of the 2198 sensor modules of the ITS is about 13,000. The target alignment precision is well below 10 micron in some cases (pixels). The sources of alignment information include survey measurements, and the reconstructed tracks from cosmic rays and from proton-proton collisions. The main track-based alignment method uses the Millepede global approach. An iterative local method was developed and used as well. We present the results obtained for the ITS alignment using about 10^5 charged tracks from cosmic rays that have been collected during summer 2008, with the ALICE solenoidal magnet switched off.Peer reviewe

Transverse momentum spectra of charged particles in proton-proton collisions at s=900\sqrt{s} = 900 GeV with ALICE at the LHC

The inclusive charged particle transverse momentum distribution is measured in proton-proton collisions at $\sqrt{s} = 900$ GeV at the LHC using the ALICE detector. The measurement is performed in the central pseudorapidity region $(|\eta|<0.8)$ over the transverse momentum range $0.15<p_{\rm T}<10$ GeV/$c$. The correlation between transverse momentum and particle multiplicity is also studied. Results are presented for inelastic (INEL) and non-single-diffractive (NSD) events. The average transverse momentum for $|\eta|<0.8$ is $\left<p_{\rm T}\right>_{\rm INEL}=0.483\pm0.001$ (stat.) $\pm0.007$ (syst.) GeV/$c$ and \left_{\rm NSD}=0.489\pm0.001 (stat.) $\pm0.007$ (syst.) GeV/$c$, respectively. The data exhibit a slightly larger $\left<p_{\rm T}\right>$ than measurements in wider pseudorapidity intervals. The results are compared to simulations with the Monte Carlo event generators PYTHIA and PHOJET.Comment: 20 pages, 8 figures, 2 tables, published version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/390

The ALICE experiment at the CERN LHC

ALICE (A Large Ion Collider Experiment) is a general-purpose, heavy-ion detector at the CERN LHC which focuses on QCD, the strong-interaction sector of the Standard Model. It is designed to address the physics of strongly interacting matter and the quark-gluon plasma at extreme values of energy density and temperature in nucleus-nucleus collisions. Besides running with Pb ions, the physics programme includes collisions with lighter ions, lower energy running and dedicated proton-nucleus runs. ALICE will also take data with proton beams at the top LHC energy to collect reference data for the heavy-ion programme and to address several QCD topics for which ALICE is complementary to the other LHC detectors. The ALICE detector has been built by a collaboration including currently over 1000 physicists and engineers from 105 Institutes in 30 countries. Its overall dimensions are 161626 m3 with a total weight of approximately 10 000 t. The experiment consists of 18 different detector systems each with its own specific technology choice and design constraints, driven both by the physics requirements and the experimental conditions expected at LHC. The most stringent design constraint is to cope with the extreme particle multiplicity anticipated in central Pb-Pb collisions. The different subsystems were optimized to provide high-momentum resolution as well as excellent Particle Identification (PID) over a broad range in momentum, up to the highest multiplicities predicted for LHC. This will allow for comprehensive studies of hadrons, electrons, muons, and photons produced in the collision of heavy nuclei. Most detector systems are scheduled to be installed and ready for data taking by mid-2008 when the LHC is scheduled to start operation, with the exception of parts of the Photon Spectrometer (PHOS), Transition Radiation Detector (TRD) and Electro Magnetic Calorimeter (EMCal). These detectors will be completed for the high-luminosity ion run expected in 2010. This paper describes in detail the detector components as installed for the first data taking in the summer of 2008

Algorithms and methods for particle identification with ALICE TOF detector at a very high particle multiplicity

The algorithms and methods for particle identification with ALICE TOF detector at a very high particle multiplicity were studied. The matching of the information acquired by TOF with the tracking data were realized by using the Kalman filtering method. The study showed that all the tracking and timing information enabled the particle identification (PID). (Edited abstract) 7 Refs

Influence of the Time Resolution of the Time of Flight System in ALICE on the Measurement of Observables

The influence of the ALICE time-of-flight resolution on the main observables has been studied. The effect of a resolution of 100 and 300 ps has been simulated for the event-by-event variables (slopes and K/&pi; ratios), for the &thorn; detection in the K-K channel and for the open charm detection

EbyE identified particle spectra and K/pi ratios using the TOF information

The latest simulations of PID efficiency and contamination have been applied to individual events generated by SHAKER and HIJING to build identified particle spectra. These spectra have been used to extract the inverse slopes for individual events for pi±, K± and pp' well as the K/pi ratios. The results obtained studying 25 events are shown

Influence of pixel occupancy on particle identification efficiency and contamination in ALICE TOF

momentum of the particles... Figure 13: The dependence of the efficiency and the contamination of track matching on the length of the pixel... Figure 14: The dependence of the efficiency and the contamination of track matching on pixel occupancy for SHAKER... Figure 15: The dependence of the efficiency and the contamination of track matching on pixel occupancy for SHAKER and HIJING generators... Figure 16: The dependence of the efficiency and the contamination of track matching on pixel occupancy for different input charged particle densities dNch/dy of SHAKER... Figure 17: The dependence of the efficiency and the contamination of track matching on pixel occupancy for two radius of the TPC... Figure 18: The dependence of the efficiency and the contamination of track matching on pixel occupancy for two values of the TPC thickness... Figure 19: The dependence of the efficiency and the contamination of track matching on pixel occupancy for two radius of TOF... Figure 20: Mass separation obtained from the TOF barrel (sigma=100ps) for electrons, pions, kaons and protons as a function of momentum ( 3 SHAKER events). Figure 21: Efficiency and contamination of PID vs momentum... Figure 22: Efficiency and contamination of PID vs occupancy... </UL