ALICE is the heavy-ion experiment at the CERN Large Hadron Collider. The experiment continuously took data during the first physics campaign of the machine from fall 2009 until early 2013, using proton and lead-ion beams. In this paper we describe the running environment and the data handling procedures, and discuss the performance of the ALICE detectors and analysis methods for various physics observables.

The ratio of the yields of antiprotons to protons in pp collisions has been measured by the ALICE experiment at sqrt[s]=0.9 and 7 TeV during the initial running periods of the Large Hadron Collider. The measurement covers the transverse momentum interval 0.45

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The first measurement of neutron emission in electromagnetic dissociation of ^{208}Pb nuclei at the LHC is presented. The measurement is performed using the neutron zero degree calorimeters of the ALICE experiment, which detect neutral particles close to beam rapidity. The measured cross sections of single and mutual electromagnetic dissociation of Pb nuclei at sqrt[s(NN)]=2.76 TeV with neutron emission are σ(singleEMD)=187.4 ± 0.2(stat)(-11.2)(+13.2) (syst) b and σ(mutualEMD) = 5.7 ± 0.1(stat) ± 0.4(syst) b, respectively. The experimental results are compared to the predictions from a relativistic electromagnetic dissociation model.

Abstract.Particle identification is an important feature of the ALICE detector at the LHC. In particular, for particle identification via the time-of-flight technique, the precise determination of the event collision time represents an important ingredient of the quality of the measurement. In this paper, the different methods used for such a measurement in ALICE by means of the T0 and the TOF detectors are reviewed. Efficiencies, resolution and the improvement of the particle identification separation power of the methods used are presented for the different LHC colliding systems (pp, p-Pb and Pb-Pb) during the first period of data taking of LHC (Run 1). IntroductionThe main task of the ALICE experiment [1,2] at the LHC is the study of the properties of the strongly interacting, dense and hot matter created in high-energy heavy-ion collisions. Many physics analyses are based on the capability of the ALICE detector to perform Particle IDentification (PID) using different and complementary techniques. In the intermediate momentum range (from 0.5 to 3-4 GeV/c) this task is mainly accomplished using the time-of-flight measurements which rely on a precise determination of the event collision time, the track length and momentum, and the arrival time of the tracks to the Time-of-flight (TOF) detector.The track length and momentum measurement is defined by the Inner Tracking System (ITS) and the Time Projection Chamber (TPC) [3]. The ITS is composed of six cylindrical layers of silicon detectors, located at radial distances between 3.9 and 43 cm from the beam axis. The TPC is a large volume cylindrical chamber with highgranularity readout that surrounds the ITS covering the region 85 < r < 247 cm and −250 < z < 250 cm in the radial r and longitudinal z directions, respectively. These detectors, covering the pseudo-rapidity interval −0.9 ≤ η ≤ 0.9 for tracks reaching the outer layer of the TPC, also provide PID information via the specific energy loss (dE/dx) measurements.The measurement of the time of flight of the tracks is based on the TOF detector. On the other hand, the event collision time t ev is determined with the information coming from both the TOF and the T0 detectors.The TOF system [4] covers the pseudo-rapidity interval −0.9 ≤ η ≤ 0.9 and full azimuthal acceptance. The system is located, according to a cylindrical symmetry, at an average distance of 3.8 m from the beam pipe spanning an active area of 141 m 2 . The detector is made of 1593 Multi-gap Resistive Plate Chambers (MRPC), with a sensitive area of 7.4 × 120 cm 2 each. Each MRPC is segmented into 96 readout pads of area 2.5 × 3.5 cm 2 . The MRPCs are packed then in five modules for each of the 18 azimuthal sectors of the ALICE spaceframe in a "TOF supermodule", as shown in fig. 1. This detector has a time resolution of ∼ 80 ps during the data taking [5].The T0 detector [6] consists of two arrays of Cherenkov counters T0A and T0C, positioned on both sides of the interaction point (IP) at a distance of 374 cm and −70 cm (as shown in fig. 2), covering ...