The ALICE Glance Shift Accounting Management System (SAMS)

Commissioning and first performances of the ALICE MID RPCs

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.

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.

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.

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.

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 a heavy-ion detector studying the physics of strongly interacting matter and the quarkgluon plasma at the CERN LHC (Large Hadron Collider). During the second long shut-down of the LHC, the ALICE detector was upgraded to cope with an interaction rate of 50 kHz in Pb-Pb collisions, producing in the online computing system (O2) a sustained input throughput of 3.5 TB/s. In the past years, the O2/FLP project built the new data-acquisition system capable of handling this load. It consists of 200 readout nodes, collecting the data transferred from over 8000 detector links to PCs memory by dedicated PCI boards. The readout software manages the hardware and software memory buffers used for DMA and inter-process communication. It initiates the data flow, performs on-the-fly consistency checks, formats the data, reports performance, and finally pushes the data to the local processing pipeline. The output is then sent by the data distribution software over 100Gb/s links to a dedicated event processing farm. The readout software modular design allowed to address the manifold needs faced during the prototyping, installation and commissioning phases, which proved essential from the lab tests to physics production, like file replay and recording, or online multi-threaded LZ4 compression. We will describe the hardware and software implementation of the O2 readout system, and review the challenges met during the commissioning and first months of operation with LHC collisions in 2022.

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.

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.

A Large Ion Collider Experiment (ALICE) at the Large Hadron Collider (LHC) is planing to upgrade its Time Projection Chamber (TPC) due to the expected higher Pb-Pb collision-rates in the next running period (Run 3) of the LHC starting in 2020. In the upgraded TPC, Gas Electron Multiplier (GEM) chambers and continuous readout system will replace Multi-Wire Proportional (MWP) chambers and conventional triggered readout. In the continuous readout, GEM signals will be processed using a 32 channel SAMPA ASIC. The first version of the SAMPA (MPW1) was delivered in 2014 and the production of final version is in progress. In this paper, the test results obtained for charge injection to the device using pulse generator as well as GEM detector prototype are reported.

Sources of machine-induced background in the ATLAS and CMS detectors at the CERN Large Hadron Collider

In December 2009 the ATLAS experiment at the CERN Large Hadron Collider (LHC) recorded the first proton-proton collisions at a center-of-mass energy of 900 GeV and this was followed by the unprecedented energy of 7 TeV in March 2010. The SemiConductor Tracker (SCT) is the key precision tracking device in ATLAS, made up from silicon microstrip detectors processed in the planar p-in-n technology. The completed SCT has been installed inside the ATLAS experimental hall. After the commissioning phase it arrived to the first LHC pp collision runs in very good shape: 99.3% of the SCT modules are operational, noise occupancy and hit efficiency exceed the design specifications, the alignment is already close enough to the ideal one to allow on-line track reconstruction and invariant mass determination. This overview presents the current status of the SCT, including results from the latest data-taking periods in 2009 and 2010, and from the detector alignment. We report on the operation of the detector and observed problems. The main emphasis is given to the performance of the SCT with the LHC in collision mode in a comparison with the expected parameters and with the Monte-Carlo simulations.

In December 2009 the ATLAS experiment at the CERN Large Hadron Collider (LHC) recorded the first proton-proton collisions at a centre-of-mass energy of 900 GeV, followed by the unprecedented energy of 7 TeV in March 2010. The Semi-Conductor Tracker (SCT) is a key precision tracking device in ATLAS, made of p-in-n-type silicon micro-strip detectors. The completed SCT has been installed inside the ATLAS experimental hall. After the commissioning phase it was in very good shape for the first LHC collision runs: 99.3% of the SCT strips are operational, noise occupancy and hit efficiency exceed the design specifications, and the alignment is already close enough to the ideal one to allow on-line track reconstruction and invariant mass determination. This paper reviews the current status of the SCT, including results from the latest data-taking periods in 2009 and 2010, and from the detector alignment. The operation of the detector and observed problems are discussed, with emphasis on the performance of the SCT with the LHC in collision mode in comparison with the expected parameters and with the Monte Carlo simulations.

The CERN Large Hadron Collider (LHC) is designed to collide proton beams of unprecedented energy, in order to extend the frontiers of high-energy particle physics. During the first very successful running period in 2010--2013, the LHC was routinely storing protons at 3.5--4 TeV with a total beam energy of up to 146 MJ, and even higher stored energies are foreseen in the future. This puts extraordinary demands on the control of beam losses. An un-controlled loss of even a tiny fraction of the beam could cause a superconducting magnet to undergo a transition into a normal-conducting state, or in the worst case cause material damage. Hence a multi-stage collimation system has been installed in order to safely intercept high-amplitude beam protons before they are lost elsewhere. To guarantee adequate protection from the collimators, a detailed theoretical understanding is needed. This article presents results of numerical simulations of the distribution of beam losses around the LHC that have leaked out of the collimation system. The studies include tracking of protons through the fields of more than 5000 magnets in the 27 km LHC ring over hundreds of revolutions, and Monte-Carlo simulations of particle-matter interactions both in collimators and machine elements being hit by escaping particles. The simulation results agree typically within a factor 2 with measurements of beam loss distributions from the previous LHC run. Considering the complex simulation, which must account for a very large number of unknown imperfections, and in view of the total losses around the ring spanning over 7 orders of magnitude, we consider this an excellent agreement. Our results give confidence in the simulation tools, which are used also for the design of future accelerators.

The ATLAS detector at CERN's Large Hadron Collider (LHC) will be exposed to proton-proton collisions from beams crossing at 40 MHz. A three-level trigger system will select potentially interesting events in order to reduce the read-out rate to about 200 Hz. The first trigger level is implemented in custom-built electronics and makes an initial fast selection based on detector data of coarse granularity. It has to reduce the rate by a factor of to less than 100 kHz. The other two consecutive trigger levels are in software and run on PC farms. We present an overview of the first-level central trigger and the muon barrel trigger system and report on the current installation status. Moreover, we show analysis results of cosmic-ray data recorded in situ at the ATLAS experimental site with final or close-to-final hardware.