ALICE Event Display -- from the legacy ROOT-based visualization to the web-based application

This paper briefly discusses the ALICE machine background concerns and the background monitoring system. ALICE RUNNING STRATEGY ALICE (A Large Ion Collider Experiment) [1] is a general purpose detector designed to address the physics of strongly interacting matter and the quark-gluon plasma in nucleus-nucleus collisions at the LHC. It will allow a comprehensive study of particles produced in Pb–Pb collisions, up to the highest multiplicities anticipated at the LHC. The physics program also includes collisions with lighter ions as well as dedicated proton-nucleus runs. Regular data taking during pp runs will provide reference data for the heavy ion program and address a number of specific pp topics. The pp runs will be in parallel with the other experiments but at a reduced luminosity in IP2. In order to keep the pile-up in the Time Projection Chamber (TPC) and Silicon Drift Detectors (SDD) at an acceptable level, the luminosity during pp runs has to be limited to 3 × 10 cm−2s−1, corresponding to an interaction rate of 200 kHz. At this rate we record on average 20 overlapping events. The optimal detector operation and physics performance with the TPC, i.e. no pile-up, is at 10 cm−2s−1. IMPACT OF MACHINE BACKGROUND General considerations Due to the running at reduced luminosity ALICE has the most unfavorable interaction rate over background rate ratio (at least a factor of 10 less than the high luminosity experiments). Machine background effects are alleviated by the fact that ALICE has been designed to perform tracking for up to 1000 times the pp multiplicity and the trigger reduction factors are relatively small (typically 10). So far the expected effects of the background are mainly of cumulative nature, such as radiation damage (integral dose and neutron fluences). Also the increase of the data volume has obvious negative consequences in terms of data storage and offline computing requirements. To simulate these effects ALICE has so far considered beam gas events in the experimental region IP ±20 m and beam-halo from beam-gas scattering outside the experimental regions. Input for the quartiary background caused by tertiary collimators (TCT) close to the experimental region is not yet available for IP2. In case the collimators are at the nominal settings this contribution could well be the dominant source of machine background. However, since at full beam intensity ALICE will run at high β∗ (10 m), the inner triplet will not limit the aperture of the machine. ALICE requires that for stable beams the TCTs will be put at a position at which they protect the inner triplets against accidental losses but do not produce extra losses for stable beams. Dose in central detectors The radiation environment in the experimental cavern has been simulated for the planned running scenario of the ALICE experiment (Table 1) [2]. Running with p-p, low and high mass ion–ion collisions over a ten year period has been assumed. Beam-beam and beam-gas interactions have been considered as potential radiation sources. The highest doses, up to 2.8 kGy, are expected at the location of the inner tracking system (ITS) (Table 2). The contribution from beam halo [3] amounts to ≈ 20% of the total dose. The contribution from beam-gas collisions within the experimental region has been calculated assuming a very conservative residual gas pressure of 2× 10 molecules/m. Only under these conditions a sizeable contribution of about 10% of the total dose is expected. Charged particle rates on RPCs Among the ALICE detectors, the muon trigger system is one of the most sensitive to the machine induced background. As a matter of fact, the Resistive Plate Chambers (RPC) rate capability (50 − 100 Hz/cm) might be saturated by a too high background level, which might also have an impact on the detector lifetime. The fluxes of secondary charged particles through muon trigger system originating from machine induced background has been simulated [4]. The trigger background consists mainly of electrons from hadronic showers resulting in a hot spot of ≈ 60 Hz/cm located at x = 1.5 m and |y| < 1.5 m. BACKGROUND MONITORING For machine background monitoring during injection ALICE will use the beam condition monitor (BCM) and the V0 forward scintillator detectors at safe photomultiplier settings. Due to the different acceptance of the two detectors an OR of the two signals will be used. With circulating stable beams a combination of signals from BCM, V0, SPD, TPC and forward muon spectrometer will be used to obtain a normalized machine background signal. Beam condition monitors The purpose of the Beam Condition Monitor (BCM) is to detect adverse beam conditions within the ALICE experLHC Workshop on Experimental Conditions and Beam-Induced Detector Backgrounds

Commissioning and first performances of the ALICE MID RPCs

ALICE is a dedicated heavy-ion experiment at CERN LHC aiming to study the properties of the quark–gluon plasma. A lead– lead collision might produce several ten thousand new particles. Detailed study of the event requires precise measurements of the particle tracks. A 90 m Time Projection Chamber (TPC) with more than 500 000 read-out pads was built as the main central barrel tracker. Collisions can be recorded at a rate of up to about 1 kHz. The front-end electronics, designed from FPGAs and custom ASICs, performs shaping, amplification, digitisation and digital filtering of the signals. The data is forwarded to DAQ via 216 1.25 Gb/s fibre-optical links. Configuration, control and monitoring is done by an embedded Linux system on the front-end electronics. First results on the performance of the front-end electronics and the distributed detector control system are presented. I. TIME PROJECTION CHAMBER (TPC) The A Large Ion Collider Experiment (ALICE) [1] is using a TPC [2] as the main track-finding detector. A TPC is a gaseous detector. It is shaped like an horizontal barrel and positioned in the same direction as the beam pipe, which is passing through the centre of the barrel. The overall length is 500 cm, divided by a 100 kV Central Electrode (CE) into two identical drift volume. The diameter is 494 cm, though the innermost 170 cm is not part of the TPC to make room for the beam pipe and inner tracking detectors. A schematic view of the TPC can be seen in Figure 1. Collisions will take place in the beam pipe in the centre of the TPC, allowing the particles produced to traverse the TPC and leave tracks of ionised gas along their paths. A strong electric field of from the CE will make the electrons drift towards the end planes, where data read-out is performed. Each end plane is divided into 18 azimuthal sectors, which again are divided into two Multi-Wire Proportional Chambers (MWPC), the Outer and Inner Read-Out Chamber (OROC/IROC). The OROC has four Read-out Partitions (RPs); the IROC two. A RP is an electronic entity for reading out data from read-out pads. The ionistic signal will be amplified by the space charge around the wires of the MWPC. The induced charge on the read-out pads is forwarded to the read-out electronics. In total for both sides there are 557568 pads. The drift volume is filled with counting gas composed of 85.7 % Ne, 9.5 % CO2 and 4.8 % N2. A cold, light gas is used to assure low diffusion and low multiple scattering. Field distortions are minimised because of the high ion mobility and few ionisation electrons per unit length. The electronics design noise figure is 1000 RMS e− (700 actually achieved); not limiting the position resolution will require a signal/noise ratio of at least 20. Apart from tracking—measuring the charged particle momentum and having a good two-track separation—it also provides Particle IDentification (PID). The TPC is expected to perform well at multiplicities as high as dNch/dη=8000 in the particle momentum range [0.1, 100] GeV/c and within |η| 90 %, and the dE/dx resolution better than 10 %. Further, the TPC alone will have a momentum resolution of about 1 % at 2 GeV/c and 10 % at 50 GeV/c. For p–p collisions a read-out rate of ≈1 kHz is expected, while for central Pb–Pb collisions ≈0.2 kHz. Figure 1: Schematic view of the TPC. To the left a singe Read-out Partition (RP) is enlarged for visibility. The support for the sectors is shown on the two end planes. Between them is the Central Electrode (CE). The TPC allows space around the centre of the length axis for beam pipe and inner silicon detectors. II. DATA READ-OUT DESIGN As already mentioned, each sector has six RPs. A RP consists of a Read-out Control Unit (RCU) with up to 25 Front-End Cards (FEC), depending on the radial location. The innermost RPs have the highest number of FECs, as a smaller size for the readout-pads is used to increase the resolution to take into account the higher track density close to the collisions. The electronics for one RP, as well as its connection to the central systems is shown as a block diagram in Figure 2. Eight ALICE TPC Read-Out (ALTRO) [3] chips are mounted on a FEC, each capable of reading out 16 read-out pads. The FECs are attached to the RCU via buses; one for data transfer and one for control/monitoring. Once on the RCU, the data is forwarded to Data Acquisition system (DAQ) and the High Level Trigger (HLT) via a 1.25 Gb/s optical fibre. A Detector Control System (DCS) board equipped with an embedded

A Large Ion Collider Experiment (ALICE) is one of the four major experiments at the Large Hadron Collider (LHC) at CERN. The high level trigger (HLT) is a compute cluster, which reconstructs collisions as recorded by the ALICE detector in real-time. It employs a custom online data-transport framework to distribute data and workload among the compute nodes. ALICE employs subdetectors that are sensitive to environmental conditions such as pressure and temperature, e.g., the time projection chamber (TPC). A precise reconstruction of particle trajectories requires calibration of these detectors. Performing calibration in real time in the HLT improves the online reconstructions and renders certain offline calibration steps obsolete speeding up offline physics analysis. For LHC Run 3, starting in 2020 when data reduction will rely on reconstructed data, online calibration becomes a necessity. Reconstructed particle trajectories build the basis for the calibration making a fast online-tracking mandatory. The main detectors used for this purpose are the TPC and Inner Tracking System. Reconstructing the trajectories in the TPC is the most compute-intense step. We present several improvements to the ALICE HLT developed to facilitate online calibration. The main new development for online calibration is a wrapper that can run ALICE offline analysis and calibration tasks inside the HLT. In addition, we have added asynchronous processing capabilities to support long-running calibration tasks in the HLT framework, which runs event-synchronously otherwise. In order to improve the resiliency, an isolated process performs the asynchronous operations such that even a fatal error does not disturb data taking. We have complemented the original loop-free HLT chain with ZeroMQ data-transfer components. The ZeroMQ components facilitate a feedback loop that inserts the calibration result created at the end of the chain back into tracking components at the beginning of the chain, after a short delay. All these new features are implemented in a general way, such that they have use-cases aside from online calibration. In order to gather sufficient statistics for the calibration, the asynchronous calibration component must process enough events per time interval. Since the calibration is valid only for a certain time period, the delay until the feedback loop provides updated calibration data must not be too long. A first full-scale test of the online calibration functionality was performed during 2015 heavy-ion run under real conditions. Since then, online calibration is enabled and benchmarked in 2016 proton-proton data taking. We present a timing analysis of this first online-calibration test, which concludes that the HLT is capable of online TPC drift time calibration fast enough to calibrate the tracking via the feedback loop. We compare the calibration results with the offline calibration and present a comparison of the residuals of the TPC cluster coordinates with respect to offline reconstruction.

The quark-gluon plasma, or QGP, is a state of matter in which quarks and gluons, the elementary building blocks of ordinary baryonic matter (as protons and neutrons), are no longer confined into hadrons by the strong force. A phase transition from ordinary nuclear matter to a QGP is expected to occur in extreme conditions of high baryon density and temperature, as is thought to have characterized the Universe about 1–10 μs after the Big Bang or can be reached in the dense cores of neutron stars. In the laboratory, the conditions of high energy density necessary to form a QGP can be obtained by colliding heavy ions at velocities close to the speed of light. The experimental investigation of the QGP provides a test of Quantum Chromodynamics (QCD), the quantum field theory within the Standard Model of elementary particles describing the interaction among color charges. A QGP is an extended many-body system of color charges whose characteristics emerge from the fundamental properties of the strong interaction at high energy densities. Understanding the phenomenology of this state of matter is therefore an important step in the understanding of the strong interaction itself and of QCD. Following the first theoretical speculations about the existence of the QGP dating back to the 1970s, the field of experimental heavy-ion physics was established through the 1970s–1980s, first at the Bevalac at the Lawrence Livermore National Laboratory (USA), then at the Alternating Gradient Synchrotron at the Brookhaven National Laboratory (BNL, USA) and the Super Proton Synchrotron (SPS) at CERN, Switzerland. In the year 2000, the discovery of the QGP was announced at the CERN SPS. Since then, the major particle and nuclear physics laboratories all around the world have been running or planning a heavy-ion experimental program, covering a broad range of collision energies. The longest and most intensive heavy-ion studies have been pursued at the BNL Relativistic Heavy Ion Collider and at the CERN Large Hadron Collider (LHC), where they are still ongoing. In parallel, numerous advances on the theoretical side, partly also helped by the increase in computing power over time, have provided more and more sophisticated tools to describe the phenomenology of heavy-ion collisions and the properties of the QGP. Even if a QGP can be produced in the laboratory under appropriate conditions, its direct observation is not possible, because the matter created in the collision exists in a deconfined state for a time of the order of 10−23 s, after which it transitions to a system of hadrons. This represents a major challenge toward the characterization of a QGP: reliance on the measurement of final-state hadronic observables and select probes that are sensitive to the QGP properties of interest at different stages of its evolution is necessary. This requires the capability to disentangle the effects due to the presence of a QGP medium from many others, including those due to the presence of a nuclear environment in the target, or from reinteractions in the final hadronic stage. At the CERN LHC in Geneva, in an underground tunnel across the border between France and Switzerland, protons and fully ionized heavy ions are accelerated and collide at energies of a few TeV per nucleon pair, the largest ever reached in a particle accelerator, recreating the conditions present in the early Universe. A Large Ion Collider Experiment (ALICE) is the experiment specifically designed to study the QGP produced at the LHC. Operating at the energy frontier since 2009, ALICE has carried out a successful physics program that has enabled a quantitative assessment of the properties of the QGP produced in heavy-ion collisions at the LHC and led to some new discoveries. The results of ALICE and the other LHC experiments have also posed new questions related to the limits of QGP formation in different collision systems, thus prompting new advances in the theoretical field.

All major experiments need tools that provide a way to keep a record of the events and activities, during both commissioning and operations. In ALICE (A Large Ion Collider Experiment) at CERN, this task is performed by the ALICE Electronic Logbook (eLogbook), a custom-made application developed and maintained by the Data-Acquisition team (DAQ), the group which within the collaboration has the responsibility for Data Acquisition. Started as a statistics repository, the eLogbook has evolved to become not only a fully functional electronic logbook, but also a massive information repository used to store the conditions and statistics of the several online systems. It is currently used by more than 1000 users in 50 different countries and it plays an important role in the daily ALICE collaboration activities. This paper will describe the LAMP (Linux, Apache, MySQL and PHP) based architecture of the eLogbook, the database schema and the relevance of the information stored in the eLogbook to the different ALICE actors, not only for near real time procedures but also for long term analysis. It will also present the web interface, including the different used technologies, the implemented security measures and the current main features. Finally it will present the roadmap for the future, including both technical and functional developments.

ALICE (A Large Ion Collider Experiment) is the heavy-ion experiment at the Large Hadron Collider (LHC) at CERN. As an important part of its upgrade plans, the ALICE experiment will schedule the installation of a new Inner Tracking System (ITS) during the Long Shutdown 2 (LS2) of the LHC. The new ITS layout will consist of seven concentric layers, $\approx$ 12.5 Gigapixel camera covering about 10m$^2$ with Monolithic Active Pixel Sensors (MAPS). This choice of technology has been guided by the tight requirements on the material budget of 0.3$\%$ X/X$_0$ per layer for the three innermost layers and backed by the significant progress in the field of MAPS in recent years. The technology initially chosen for the ITS upgrade is the TowerJazz 180 nm CMOS Technology. It offers a standard epitaxial layer of 15 - 18 $\mu$m with a resistivity between 1 and 5 k$\Omega$~cm$^{-1}$ and a gate oxide thickness below 4 nm, thus being more robust to Total Ionizing Dose (TID). The main subject of this thesis is to implement a novel digital pixel readout architecture for MAPS. This thesis aims to study this novel readout architecture as an alternative to the rolling-shutter readout. However, this must be investigated through the study of several chip readout architectures during the R$\&$D phase. Another objective of this thesis is the study and characterization of TowerJazz, if it meets the Non-Ionizing Energy Loss (NIEL) and Single Event Effects (SEE) of the ALICE ITS upgrade program. Other goals of this thesis are: Implementation of the top-down flow for this CMOS process and the design of multiple readouts for different prototypes up to the assembly of a full-scale prototype. Characterization of the radiation hardness and SEE of the chips submitted to fabrication. Characterization of full custom designs using analog simulations and the generation of digital models for the simulation chain needed for the verification process. \item Implementation and study of different digital readouts to meet the ITS upgrade program in integration time, pixel size and power consumption, from the conceptual idea, production and fabrication phase. SChapter 1 is a brief overview of CERN, the LHC and the detectors complex. The ALICE ITS will be explained, focusing on the ITS upgrade in terms of detector needs and design constraints. Chapter 2 explains the properties of silicon detectors and the detector material and the principles of operation for MAPS. Chapters 3 and 4 describe the ALPIDE prototypes and their readout based on MAPS; this forms the central part of this work, including the multiple families of pixel detectors fabricated in order to reach the final design for the ITS. The ALPIDE3/pALPIDE3B chip, the latest MAPS chip designed, will be explained in detail, as well focusing in the matrix digital readout. In chapter 5 the noise measurements and its characterization are presented including a brief summary of detector response to irradiation with soft X-rays, sources and particle beams. on the ITS upgrade in terms of detector needs and design constraints. Chapter 2 explains the properties of silicon detectors and the detector material and the principles of operation for MAPS. Chapters 3 and 4 describe the ALPIDE prototypes and their readout based on MAPS; this forms the central part of this work, including the multiple families of pixel detectors fabricated in order to reach the final design for the ITS. The ALPIDE3/pALPIDE3B chip, the latest MAPS chip designed, will be explained in detail, as well focusing in the matrix digital readout. In chapter 5 the noise measurements and its characterization are presented including a brief summary of detector response to irradiation with soft X-rays, sources and particle beams.

ALICE (A Large Ion Collider Experiment) studies the Quark-Gluon Plasma (QGP): a deconfined state of nuclear matter obtained in ultra-relativistic heavy-ion collisions. One of the key probes for QGP characterization is the study of quarkonia and open heavy flavor production, of which ALICE exploits the muonic decay. In particular, a set of Resistive Plate Chambers (RPCs), placed in the forward rapidity region of the ALICE detector, is used for muon identification purposes.The correct operation of these detectors is ensured by the choice of the proper gas mixture. Currently they are operated with a mixture of C2H2F4, i-C4H10 and SF6 but, starting from 2017, new EU regulations have enforced a progressive phase-out of C2H2F4 because of its large Global Warming Potential (GWP), which is making it difficult and costly to purchase. Moreover, CERN asked LHC experiments to reduce greenhouse gases emissions, to which RPC operation contributes significantly.A possible candidate for C2H2F4 replacement is the C3H2F4 (diluted with other gases, such as CO2), which has been extensively tested using cosmic muons. Promising gas mixtures have been devised; the next crucial steps are the detailed in-beam characterization of such mixtures as well as the study of their performance under increasing irradiation levels.This contribution will describe the methodology and results of beam tests carried out at the CERN Gamma Irradiation Facility (equipped with a high activity 137Cs source and muon beam) with an ALICE-like RPC prototype, operated with several mixtures with varying proportions of CO2, C3H2F4, i-C4H10 and SF6 . Absorbed currents, efficiencies, prompt charges, cluster sizes, time resolutions and rate capabilities will be presented, both from digitized (for detailed shape and charge analysis) and discriminated (using the same front-end electronics as employed in ALICE) signals.

ALICE (A Large Ion Collider Experiment) is one of the four major detectors located at the LHC at CERN, focusing on the study of heavy-ion collisions. The ALICE High Level Trigger (HLT) is a compute cluster which reconstructs the events and compresses the data in real-time. The data compression by the HLT is a vital part of data taking especially during the heavy-ion runs in order to be able to store the data which implies that reliability of the whole cluster is an important matter. To guarantee a consistent state among all compute nodes of the HLT cluster we have automatized the operation as much as possible. For automatic deployment of the nodes we use Foreman with locally mirrored repositories and for configuration management of the nodes we use Puppet. Important parameters like temperatures, network traffic, CPU load etc. of the nodes are monitored with Zabbix. During periods without beam the HLT cluster is used for tests and as one of the WLCG Grid sites to compute offline jobs in order to maximize the usage of our cluster. To prevent interference with normal HLT operations we separate the virtual machines running the Grid jobs from the normal HLT operation via virtual networks (VLANs). In this paper we give an overview of the ALICE HLT operation in 2016.

A Large Ion Collider Experiment (ALICE) experiment is one of the four experiments at the Large Hadron Collider (LHC) designed to investigate the status of matter under very high energy densities produced during heavy-ion collisions. The ALICE inner tracking system (ITS) consists of seven concentric cylindrical layers of monolithic silicon pixel sensors known as ALICE pixel detector (ALPIDE). The sensors are used to reconstruct the paths of charged particles generated in the collisions. The sensor alignment of the detector must be adjusted to a high precision standard. The adjustment objective is to obtain a detector that can undertake high-resolution measurements. This paper introduces a method for measuring the reference markers utilized in sensor alignment determination. Markers engraved at the chip corners have been detected using the Hough transform, Canny edge detection, and template matching techniques. The distances between two markers are measured to determine the accuracy of the pixel sensor alignment before and after assembly. The proposed methods exhibit an accuracy exceeding 99% and demonstrate high speed analysis. The average processing times for detecting the circle and cross markers are 105.9 ms/image and 113.8 ms/image, respectively. The sensor alignment of the detector must be adjusted to a high precision standard. However, recent studies have shown deviations of up to 5 μ m above the desired value in the measured sensor position. Such deviations do not represent a major issue, nevertheless it is important to measure them in order to speed-up and make more accurate the recursive track-based alignment procedure used to reconstruct the position of each pixel sensor in the tracking detector. The proposed method offers a promising solution to deliver precise and rapid measurements for a large number of examined objects.

CARLOSv3 is the third version of a chip that plays a significant role in the data acquisition chain of the A Large Ion Collider Experiment (ALICE) silicon drift detector (SDD). ALICE is one of the foremost high-energy physics experiments (HEPE) conducted within the Large Hadron Collider at CERN, the European Organization for Nuclear Research in Geneva. CARLOSv3 was principally designed and built for the on-line compression of the input dataset originating from a physical bidimensional silicon sensor. To compress a bidimensional dataset, a bidimensional data compressor was required. The compressor was designed for the ALICE SDD Experiment but could be applied to all experiments in which an incoming stream dataset originates from a bidimensional sensor.

ALICE (A Large Ion Collider Experiment) is an experiment at the CERN LHC (Large Hadron Collider) studying the physics of strongly interacting matter and the quark-gluon plasma.The experiment operation requires a 24 hours a day and 7 days a week shift crew at the experimental site, composed by the ALICE collaboration members. Shift duties are calculated for each institute according to their correlated members. In order to ensure the full coverage of the experiment operation as well as its good quality, the ALICE Shift Accounting Management System (SAMS) is used to manage the shift bookings as well as the needed training. ALICE SAMS is the result of a joint effort between the Federal University of Rio de Janeiro (UFRJ) and the ALICE Collaboration. The Glance technology, developed by the UFRJ and the ATLAS experiment, sits at the basis of the system as an intermediate layer isolating the particularities of the databases.In this paper, we describe the ALICE SAMS development process and functionalities. The database has been modelled according to the collaboration needs and is fully integrated with the ALICE Collaboration repository to access members information and respectively roles and activities. Run, period and training coordinators can manage their subsystem operation and ensure an efficient personnel management. Members of the ALICE collaboration can book shifts and on-call according to pre-defined rights.ALICE SAMS features a user profile containing all the statistics and user contact information as well as the Institutes profile. Both the user and institute profiles are public (within the scope of the collaboration) and show the credit balance in real time. A shift calendar allows the Run Coordinator to plan data taking periods in terms of which subsystems shifts are enabled or disabled and on-call responsible people and slots. An overview display presents the shift crew present in the control room and allows the Run Coordination team to confirm the presence of both regular and trainees shift personnel, necessary for credit accounting.

ALICE (A Large Ion Collider Experiment) is a general purpose heavy-ion experiment designed for the study of strongly-interacting matter at the extreme energy densities reached in Pb-Pb collisions at the CERN LHC, where the deconfined phase of hadronic matter known as Quark-Gluon Plasma (QGP), is formed. The innermost detector of ALICE is the Inner Tracking System. In its first release, it consists of six cylindrical layers of silicon detectors based on different technologies: two inner layers of pixel sensors (Silicon Pixel Detector), two intermediate layers of drift sensors (Silicon Drift Detector), two outer layers of strip sensors (Silicon Strip Detector). The ITS is used for the reconstruction of primary and secondary vertices, for particle tracking, for a precise determination of the impact parameter and for particle identification at low momentum. In this report, after a brief description of the three subdetectors, the operational experience with the first ITS implementation is summarized, the status and the performance of the detector are described and the lessons learned are discussed after the end of its operation coinciding with the completion of the LHC Run2.

Quark Gluon Plasma (QGP) is an unavoidable consequence of Quantum Chromodynamics (QCD). High-energy heavy-ion collisions offer the unique possibility to reproduce in the laboratory the conditions expected during the very first stages of the evolution of the Universe. The ALICE (A Large Ion Collider Experiment) experiment at the Large Hadron Collider (LHC) allows the study of the dense nuclear environment created in nucleus-nucleus collisions. Particle Identification (PID) is one of the key features of the ALICE experiment. Identified particle spectra represent a crucial tool to understand the behaviour of the matter created in high-energy heavy-ion collisions. The transverse momentum p T distributions of identified hadrons contain information about the transverse expansion of the system and constrain the freeze-out properties of the system. Hydrodynamic models have proved to be very successful reproducing a large number of features of heavy-ion collisions (e.g., particle p T distributions, radial flow, elliptic flow, Hanbury Brown-Twiss correlations, ...). The measurement of the p T distributions of identified π, K and p in Pb-Pb collisions at $$\sqrt {s_{NN} } = 2.76$$ TeV is presented and discussed in terms of hydrodynamics. The V0 detector allows the selection of events based on the eccentricity of the collision (related with the initial geometry). This makes possible the study of the correlation between the p T distribution of hadrons and elliptic flow on an event-by-event basis. Hadron abundances can be obtained from the principle of maximum entropy using statistical concepts. This allows the extrapolation of the chemical freeze-out parameters from the data. Over the last years it has been proved that the chemical freeze-out temperature T ch is connected with the phase transition temperature T C . The measurements of the freeze-out parameters at the LHC energies are described in detail and the results obtained by various groups at lower energies are extended with the inclusion of the LHC measurement. The LHC measurements cast a new light upon the hydrodynamic and thermal behaviour of the hadron production in heavy-ion collisions. The possible scenarios are described and commented.

Two particle correlations are used to extract information about the characteristic size of the system for proton-proton collisions at =900 GeV measured by the ALICE (A Large Ion Collider Experiment) detector at CERN. The correlation functions obtained show the expected Bose-Einstein effect for identical particles, but there are also long range correlations present that shift the baseline from the expected flat behavior. A possible source of these correlations is the conservation of energy and momentum, especially for small systems, where the energy available for particle production is limited. A new technique, first introduced by the STAR collaboration, of quantifying these long range correlations using energy-momentum conservation considerations is presented here. It is shown that the baseline of the two particle correlation function can be described using this technique.