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.

ALICE is a general-purpose heavy-ion experiment designed to study the physics of strongly interacting matter and the quark–gluon plasma in nucleus–nucleus collisions at the LHC. It currently involves more than 900 physicists and senior engineers, from both the nuclear and high-energy physics sectors, from over 90 institutions in about 30 countries.The ALICE detector is designed to cope with the highest particle multiplicities above those anticipated for Pb–Pb collisions (dNch/dy up to 8000) and it will be operational at the start-up of the LHC. In addition to heavy systems, the ALICE Collaboration will study collisions of lower-mass ions, which are a means of varying the energy density, and protons (both pp and pA), which primarily provide reference data for the nucleus–nucleus collisions. In addition, the pp data will allow for a number of genuine pp physics studies.The detailed design of the different detector systems has been laid down in a number of Technical Design Reports issued between mid-1998 and the end of 2004. The experiment is currently under construction and will be ready for data taking with both proton and heavy-ion beams at the start-up of the LHC.Since the comprehensive information on detector and physics performance was last published in the ALICE Technical Proposal in 1996, the detector, as well as simulation, reconstruction and analysis software have undergone significant development. The Physics Performance Report (PPR) provides an updated and comprehensive summary of the performance of the various ALICE subsystems, including updates to the Technical Design Reports, as appropriate.The PPR is divided into two volumes. Volume I, published in 2004 (CERN/LHCC 2003-049, ALICE Collaboration 2004 J. Phys. G: Nucl. Part. Phys. 30 1517–1763), contains in four chapters a short theoretical overview and an extensive reference list concerning the physics topics of interest to ALICE, the experimental conditions at the LHC, a short summary and update of the subsystem designs, and a description of the offline framework and Monte Carlo event generators.The present volume, Volume II, contains the majority of the information relevant to the physics performance in proton–proton, proton–nucleus, and nucleus–nucleus collisions. Following an introductory overview, Chapter 5 describes the combined detector performance and the event reconstruction procedures, based on detailed simulations of the individual subsystems. Chapter 6 describes the analysis and physics reach for a representative sample of physics observables, from global event characteristics to hard processes.

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The nuclear modification factor, R AA , of the prompt charmed mesons D 0 , D + and D * + , and their antiparticles, was measured with the ALICE detector in Pb-Pb collisions at a centre-of-mass energy √ s NN = 2.76 TeV in two transverse momentum intervals, 5 < p T < 8 GeV/c and 8 < p T < 16 GeV/c, and in six collision centrality classes. The R AA shows a maximum suppression of a factor of 5-6 in the 10% most central collisions. The suppression and its centrality dependence are compatible within uncertainties with those of charged pions. A comparison with the R AA of non-prompt J/ψ from B meson decays, measured by the CMS Collaboration, hints at a larger suppression of D mesons in the most central collisions.Keywords: Charm physics, Heavy Ions, Heavy-ion collision The ALICE collaboration 17 IntroductionWhen heavy nuclei collide at high energy, a state of strongly-interacting matter with high energy density is expected to form. According to Quantum Chromodynamics (QCD) calculations on the lattice, this state of matter, the so-called Quark-Gluon Plasma (QGP) is characterised by the deconfinement of the colour charge (see e.g. [1][2][3][4]). High-momentum partons, produced at the early stage of the nuclear collision, lose energy as they interact with the QGP constituents. This energy loss is expected to proceed via both inelastic (gluon radiation) [5,6] and elastic (collisional) processes [7][8][9]. The nuclear modification factor R AA is used to characterise parton energy loss by comparing particle production yields in nucleus-nucleus collisions to a scaled proton-proton (pp) reference, that corresponds to a superposition of independent nucleon-nucleon collisions. R AA is defined aswhere dσ pp /dp T and dN AA /dp T are the transverse momentum (p T ) differential cross section and yield in proton-proton and nucleus-nucleus (AA) collisions, respectively. T AA is the average nuclear overlap function, estimated within the Glauber model of the nucleusnucleus collision geometry, and proportional to the average number of nucleon-nucleon (binary) collisions [10,11]. Energy loss shifts the momentum of quarks and gluons, and thus hadrons, towards lower values, leading to a suppression of hadron yields with respect to binary scaling at p T larger than few GeV/c (R AA < 1). Energy loss is expected to be smaller for quarks than for gluons because the colour charge factor of quarks is smaller than that of gluons [5,6]. In the energy regime of the Large Hadron Collider (LHC), light-flavour hadrons with p T ranging from 5 to 20 GeV/c originate predominantly from gluon fragmentation (see e.g. As discussed in ref.[15], this should be the case also for charm and beauty quarks produced in gluon splitting processes, if their transverse momentum is lower than about 50 GeV/c. Therefore, the comparison of the heavy-flavour hadron R AA with that of pions allows the colour-charge dependence of parton energy loss to be tested. The softer fragmentation of gluons than that of charm quarks, and the observed increase of the charged hadr...