A Large Ion Collider Experiment Research Articles

ALICE upgrades during the LHC Long Shutdown 2

A Large Ion Collider Experiment (ALICE) has been conceived and constructed as a heavy-ion experiment at the LHC. During LHC Runs 1 and 2, it has produced a wide range of physics results using all collision systems available at the LHC. In order to best exploit new physics opportunities opening up with the upgraded LHC and new detector technologies, the experiment has undergone a major upgrade during the LHC Long Shutdown 2 (2019–2022). This comprises the move to continuous readout, the complete overhaul of core detectors, as well as a new online event processing farm with a redesigned online-offline software framework. These improvements will allow to record Pb-Pb collisions at rates up to 50 kHz, while ensuring sensitivity for signals without a triggerable signature.

Expected performance of the High Energy Particle Detector (HEPD-02) tracking system on board of the second China Seismo-Electromagnetic Satellite

The China Seismo-Electromagnetic Satellite (CSES) is a scientific space program that aims to deepen the comprehension of the time correlation between the main earthquake shocks and an increase in the electron flux in the inner Van Allen belt. For this purpose, the suite of payloads on board the second CSES satellite (CSES-02) consists of several detectors. The launch of CSES-02 is foreseen in 2024. The present work is focused on the second generation High-Energy Particle Detector (HEPD-02), developed by Limadou Italian collaboration, and in particular on its tracking system (Direction Detector — DD) to reconstruct the incident particle angle. The DD is made of five standalone tracking modules, consisting, as first and unique case, of monolithic silicon pixel sensors (MAPS), namely ALTAI. This chip was developed in the framework of the ALICE (A Large Ion Collider Experiment) ITS sensor studies. The results on the DD performance are discussed based on the demanding requirements of space applications.

Commissioning of the ALICE readout software for LHC Run 3

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.

Commissioning and first performances of the ALICE MID RPCs

ALICE (A Large Ion Collider Experiment) at the CERN Large Hadron Collider (LHC) is designed to study pp and Pb–Pb collisions at ultra-relativistic energies. ALICE is equipped with a Muon Spectrometer (MS) to study the heavy charmonia in pp and heavy ion collisions via their muonic decay. At first, in the LHC Run 1 and 2 the selection of interesting events for muon physics in the MS was performed with a dedicated Muon Trigger system based on Resistive Plate Chambers (RPCs) operated in maxi-avalanche mode. During the LHC Long Shutdown 2 (LS2), ALICE underwent a major upgrade of its apparatus in order to fully profit from the increased luminosity of Pb–Pb collisions (from 20 kHz in Run 2 to 50 kHz in Run 3). Many sub-systems of the ALICE experiment are now running in continuous readout (triggerless). In this context the Muon Trigger system became the Muon IDentifier (MID). In order to reduce the RPC ageing and to increase the rate capability, it was decided to use a new front-end electronics FEERIC with a pre-amplification stage to minimize the charge released per hit inside the gas gap. A description of the MID upgrades, together with the results and performances of the RPCs from the commissioning, is presented in this paper.

Development of the Readout Electronics for a MAPS-Based Beam Telescope

Along with the change of the Deutsches Elektronen-Synchrotron (DESY) II test beam facility operation mode, the existing beam telescope built with the Mimosa26 chips will be unable to meet the requirements of the much-increased beam particle rate. In this article, we present the readout electronics of a new beam telescope built with ALice PIxel Detector (ALPIDE) chips which are originally designed for the upgrade of A Large Ion Collider Experiment (ALICE). The gigabit Ethernet implemented in the high-speed transceiver of Kintex field programmable gate array (FPGA) enables individual data acquisition and control of each ALPIDE chip. The data from the multidetector plane are transmitted to the remote platform via an Ethernet switch. The global trigger is generated by an AIDA2020-trigger logic unit (TLU) by the coincidence of two pairs of plastic scintillators. The results of long-term beam tests show that the new beam telescope can achieve a lower fake hit rate and a trigger rate of 220 kHz, which increases beam utilization and reduces the difficulty of track reconstruction. The biased resolution of distribution using all six planes for tracking in a 6 GeV electron beam is measured to be about 5 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> .

Performance of the ALICE upgraded inner tracking system

Major upgrades of the ALICE (A Large Ion Collider Experiment) detector are underway and will be completed during the LHC long shutdown 2 in order to start operation in 2022 for LHC run 3. One key part of this upgrade is the new Inner Tracking System (ITS2), a full silicon-pixel detector constructed entirely with CMOS monolithic active pixel sensors. The upgraded ITS2 detector consists of three inner layers (50 μm thick sensors) and four outer layers (100 μm thick sensors) covering 10 m2 and containing 12.5 billion pixels with a pixel pitch of 27 μm × 29 μm. Compared with the silicon tracking system used during the LHC run 1 and run 2, the increased granularity, the very low material budget (0.35% X 0/layer in the inner barrel) as well as a smaller beam pipe radius, will result in a significant improvement of impact-parameter resolution and tracking efficiency. The assembly of the detector and services finished in December 2019, and the detector was fully installed in the ALICE experiment in May 2021. A comprehensive commissioning phase (on the surface) was completed in December 2020 to validate the detector performance. In this paper, an overview of the design and construction, as well as the performance of the ITS2 studied from the on-surface commissioning will be discussed in detail.

The ReadoutCard Userspace Driver for the New Alice O 2 Computing System

The ALICE (A Large Ion Collider Experiment) experiment focuses on the study of the quark-gluon plasma as a product of heavy-ion collisions at the CERN LHC (Large Hadron Collider). During the Long Shutdown 2 of the LHC in 2019-2020, a major upgrade is underway in order to cope with a hundredfold input data rate increase with peaks of up to 3.4 TB/s. This upgrade includes the new Online-Offline computing system called O2. The O2 readout chain runs on commodity Linux servers equipped with custom PCIe FPGA-based readout cards; the PCIe v3 x16, Intel Arria 10-based CRU (Common Readout Unit) and the PCIe v2 x8, Xilinx Vertex6-based CRORC (Common ReadOut Receiver Card). Access to the cards is provided through the O2 ReadoutCard userspace driver which handles synchronisation and communication for DMA transfers, provides BAR access, and facilitates card configuration and monitoring. The ReadoutCard driver is the lowest-level interface to the readout cards within O2 and is in use by all central systems and detector teams of the ALICE experiment. This communication presents the architecture of the driver, and the suite of tools used for card configuration and monitoring. It also discusses its interaction with the tangent subsystems within the O2 framework.

ALICE FIT Data Processing and Performance during LHC Run 3

During the upcoming Run 3 and Run 4 at the LHC the upgraded ALICE (A Large Ion Collider Experiment) will operate at a significantly higher luminosity and will collect two orders of magnitude more events than in Run 1 and Run 2. A part of the ALICE upgrade is the new Fast Interaction Trigger (FIT). This thoroughly redesigned detector combines, in one system, the functionality of the four forward detectors used by ALICE during the LHC Run 2: T0, V0, FMD, and AD. The FIT will monitor luminosity and background, provide feedback to the LHC, and generate minimum bias, vertex and centrality triggers, in real time. During the offline analysis FIT data will be used to extract the precise collision time needed for time-of-flight (TOF) particle identification. During the heavy-ion collisions, FIT will also determine multiplicity, centrality, and event plane. The FIT electronics is designed to function both in the continuous and the triggered readout mode. In these proceedings the FIT simulation, software, and raw data processing are briefly described. However, the main focus is on the detector performance, trigger efficiencies, collision time, and centrality resolution.

Performance and upgrade plans of the ALICE Photon Spectrometer

PHOS is a highly granulated precision spectrometer, one of the two electromagnetic calorimeters of ALICE (A Large Ion Collider Experiment) at the LHC. It is based on scintillating PbWO4 crystals and is dedicated to the precise measurements of spectra, correlations and collective flow of neutral mesons, thermal and prompt direct photons in ultra-relativistic nuclear collisions at LHC energies. PHOS participated in LHC Run 1 (2009–2013) and Run 2 (2015–2018), during which a large amount of physical data were collected in pp, p-Pb and Pb-Pb collisions.We present an overview of the PHOS performance during Runs 1 and 2 and plans for an upgrade for future LHC runs.

Heavy-flavour Measurements in Pb–Pb Collisions with the Upgraded ALICE Inner Tracking System

During the second LHC long shutdown (LS2) the Inner Tracking System (ITS) of ALICE (A Large Ion Collider Experiment) will be replaced by seven layers of CMOS Monolithic Active Pixel Sensors (MAPS). The latest innovations in silicon imaging technology allow for the construction of large, ultra-thin silicon wafers which can further improve the capabilities of the ALICE tracker. The research and development studies towards the construction of a novel vertex detector have started. The detector installation has been proposed for the third LHC long shutdown (LS3) during which the three innermost layers shall be replaced by three cylindrical layers of large curved CMOS wafers. This upgrade (ITS3) will further improve the impact parameter resolution and the tracking efficiency of low momentum particles. The innermost layer will be positioned closer to the interaction point and the material budget will be reduced down to 0.05$\%X_0$ per layer. Monte Carlo simulations of a simplified ITS3 geometry within the ITS2 design indicate an improvement in the impact parameter resolution and the tracking efficiency, which are of crucial importance for measurements of heavy-flavour hadrons. This contribution shows the improved performance for the example of the $\Lambda_{\mathrm{b}}$, for which the significance of its measurement is extracted based on these MC simulations. A significant improvement by almost a factor of three in the low momentum region compared to the ITS2 is observed.

Commissioning of the new ALICE Inner Tracking System

The upgrade of the Inner Tracking System (ITS) of ALICE (A Large Ion Collider Experiment) will extend measurements of heavy-flavour hadrons and low-mass dileptons to a lower transverse momentum than currently achieved and increase the readout capabilities to incorporate the full interaction. Furthermore, the tracking efficiency will be improved at low transverse momentum. To achieve this, the new ALICE ITS is comprised of seven layers of a custom Monolithic Active Pixel Sensor design known as ALPIDE, with a spatial resolution of 5 μm. The use of the ALPIDE-based detector design will reduce the material budget to 0.35% X0 per layer for the innermost three layers, and to 1.0% X0 per layer for the outermost four layers, compared to 1.14% X0 per layer in the previous ITS. The construction effort in numerous sites around the world has resulted in a fully assembled and connected detector, which is currently undergoing on surface commissioning before its installation in the ALICE cavern. This contribution discusses the design and the current status of the commissioning of the new ITS detector, including the methods used to characterise the detector and the results obtained so far.

Upgrade of the ALICE inner tracking system: Construction and commissioning

ALICE (A Large Ion Collider Experiment) is the CERN LHC experiment optimized for the study of the strongly interacting matter produced in heavy-ion collisions, in particular the characterization of the quark-gluon plasma. After the successful operation of the experiment during the first two runs of the LHC, the ALICE collaboration is currently working on a major upgrade of its detectors, to be installed during the 2019–2020 Long Shutdown (LS2). The main goal is to increase the readout capabilities and allow recording of Pb–Pb minimum bias events at rates in excess of 50 kHz, which is the expected Pb–Pb interaction rate at the LHC after LS2. One key part of the upgrade is the construction of a new Inner Tracking System (called ITS2) that will significantly improve the impact parameter resolution of the tracks, tracking efficiency, and readout capacity which enables precise measurements of low momentum charged particles. The ITS2 consists of seven approximately-cylindrical detector layers of CMOS Monolithic Active Pixel Sensors (MAPS) with the sensor matrix and readout integrated on a single chip, named ALPIDE (ALice PIxel DEtector), covering an area of 10 m2 and containing about 12.5 billion pixels. All layers are mounted on ultra-lightweight carbon support structures with an embedded cooling system. This allows a reduction of the material budgets down to about 0.3% X0 for the inner layers and 1% X0 for the outer layers, with respect to the previous ITS system. After a brief overview of the upgrade motivation, details of the overall layout will be given as well as the construction and commissioning status and plans.

Performance of the ALICE electromagnetic calorimeters in LHC Runs 1 and 2 and upgrade projects

ALICE (A Large Ion Collider Experiment) at the LHC is designed for studies of nuclear matter at extreme temperatures and energy densities, the so-called Quark-Gluon Plasma (QGP). Two detectors for measurements of electromagnetic signals, high-granularity photon spectrometer PHOS and large acceptance electromagnetic calorimeter EMCal/DCal, are incorporated into the ALICE detector. In order to enhance the data sample of the high-energy part of the spectra, dedicated triggers on high energetic photons or jets are used. High precision measurements of neutral mesons require fine energy and timing calibrations. Photon signal purity is improved using dedicated photon PID criteria based on cluster shape and anti-track matching with the ALICE central tracking system, as well as a special detector located in front of PHOS called CPV. PHOS and EMCal participated in LHC Run 1 (2009-2013) and Run 2 (2015-2018) during data taking periods of pp, p-Pb and Pb-Pb collisions. We give an overview of their performance in Runs 1 and 2 in low and high multiplicity environments as well as the upgrade plans for future LHC runs.

Jiskefet, a bookkeeping application for ALICE

A new bookkeeping system called Jiskefet is being developed for A Large Ion Collider Experiment (ALICE) during Long Shutdown 2, to be in production until the end of LHC Run 4 (2029). Jiskefet unifies two functionalities: a) gathering, storing and presenting metadata associated with the operations of the ALICE experiment and b) tracking the asynchronous processing of the physics data. It will replace the existing ALICE Electronic Logbook and AliMonitor, allowing for a technology refresh and the inclusion of new features based on the experience collected during Run 1 and Run 2. The front end leverages web technologies much in use nowadays such as TypeScript and NodeJS and is adaptive to various clients such as tablets, mobile devices and other screens. The back end includes an OpenAPI specification based REST API and a relational database. This paper will describe the organization of the work done by various student teams who work on Jiskefet in sequential and parallel semesters and how continuity is guaranteed by using guidelines on coding, documentation and development. It will also describe the current status of the development, the initial experience in detector stand-alone commissioning setups and the future plans.

Upgrade of pixel sensor telescope for the characterization of ALPIDE sensor

A Large Ion Collider Experiment (ALICE) is an experiment station at CERN that detects quark-gluon plasma, a state of matter thought to have formed immediately after the big bang. A plan was proposed to upgrade the particle detector in the Inner Tracking System (ITS) of ALICE by 2020. In the upgrade, new silicon sensor technology, the Monolithic Active Pixel Sensor (MAPS), will be used to replace the ITS. The new sensor is called ALICE PIxel DEtector (ALPIDE). This project focused on the characterization of ALPIDE sensors with a new version of a pixel sensor telescope using the 1.2 GeV electron beam at the Synchrotron Light Research Institute Beam Test Facility (SLRI-BTF). Seven ALPIDE sensors were lined up as a stacked sensor to perform a test using the electron beam at SLRI-BTF. The previous version of the telescope could only characterize the middle area of the sensor; however, the new sensor telescope can be used to characterize edges and corners of the sensor. This advantage provides us with a complete view of the detection efficiency in all sections of the ALPIDE sensor. The detection efficiency of the sensor will be investigated and analyzed by EUTelescope software.

Recent Results From Beam Tests of the ALPIDE Pixel Chip for the Upgrade of the ALICE Inner Tracker

The planned upgrade of the A Large Ion Collider Experiment (ALICE) inner tracking system (ITS) aims at improving the ALICE performance in terms of spatial resolution and data rate readout. The new ITS will be a low-material-budget, high-granularity detector. It comprises seven concentric layers of monolithic active pixel sensors (MAPS), called ALPIDE, which are based on the TowerJazz 180-nm CMOS technology. In this article, we report on detection performance and radiation hardness studies of ALPIDE sensors. We show that these sensors keep having high detection efficiency for minimum ionizing particles (MIPs) (>99%) and low fake-hit rate while being radiation hard to some ${ 1.7} \times { 10}^{ 13}\,\,1$ MeV $\text{n}_{\text {eq}}$ cm−2 of nonionizing energy loss (NIEL) and 2.7 Mrad of total ionization dose (TID), which exceeds the expected radiation load during the detector lifetime ten times. ALPIDE sensors thus completely fulfill the design requirements. In addition, we show that measured cluster shape frequencies obtained at different operating points (thresholds, bias voltages) are well described with the state-of-the-art ALICE Monte Carlo simulation.

A Monolithic 32-Channel Front End and DSP ASIC for Gaseous Detectors

Conseil Européen pour la Recherche Nucléaire is currently undergoing a major upgrade within the A Large Ion Collider Experiment (ALICE) detectors, one of the four main experiments at the Large Hadron Collider (LHC) accelerator. The LHC luminosity will increase making the heavy ions collision rate rise from 500 Hz to 50 kHz. Both the time projection chamber (TPC) and muon chamber (MCH) detectors demand a new and faster readout electronics, which support continuous readout to cope with this higher rate. This paper presents the serialized analog-digital multipurpose application-specific integrated circuit (ASIC) (SAMPA) integrated circuit for upgrading the TPC and MCH front-end and signal processing of charge induced signals, addressing the higher data rate specification. The SAMPA comprises 32 equal channels, twice the present ALICE TPC readout circuitry capacity. Each channel is composed of a positive/negative polarity charge sensitive amplifiers, a pulse shaper, and a 10-bit analog-to-digital converter. It also integrates a full custom digital signal processor, which receives the data from 32 channels, compensate signal perturbations or distortion through several filters and transmits the processed data. Designed for Taiwan Semiconductor Manufacturing Company 130-nm CMOS process, the manufactured chip occupies an area of approximately 85 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and consumes about 8.3 mW per channel at a nominal voltage supply of 1.25 V. The SAMPA is silicon proven and the experimental test results have confirmed its functionality and suitability for the ALICE Upgrade (2019-2020).

MAPS application in the STAR and ALICE Experiments

Abstract Monolithic Active Pixel Sensors (MAPS) offer a set of highly desirable characteristics for high precision tracking of charged particles. These characteristics include relatively high readout speed, low mass and radiation length, low power dissipation and cost and complexity savings over hybrid detectors. These features along with reasonable radiation tolerance make them ideal candidates for the current heavy ion experiments at colliders. We will describe the principles of operation and the design and performance of the MAPS used in the Soleniodal Tracker at RHIC (STAR) PiXeL (PXL) vertex detector and the A Large Ion Collider Experiment (ALICE) Inner Tracking System (ITS) upgrade. In addition, we will show that the performance at STAR demonstrates the value of the technology. We will also give the performance that is expected to be achieved with the ITS upgrade at the ALICE detector at the CERN.

An Upgraded Luminosity Leveling Procedure for the ALICE Experiment

The Large Hadron Collider (LHC) Interface project (LHC_IF) ensures that the A Large Ion Collider Experiment (ALICE) can operate congruently and safely with the LHC in different machine configurations and beam modes. Measurements in proton–proton (pp) collisions are vital for ALICE and serve as a reference to calibrate the Pb ion–Pb ion (Pb–Pb) measurements. However, during the pp operation to limit the event pile up (number of pp collisions per bunch crossing) and ensure a high-quality data sample, the instantaneous luminosity must be limited in ALICE to ${5\times 10^{30} {\text {cm}}^{-2}\,\mathrm {{s}}^{-1}}$ . This is achieved by applying a beam–beam separation in the separation plane up to several beam ${\sigma }$ (beam size unit), which is known as luminosity leveling. Given that the luminosity in a collider is expressed by a well-known formula in terms of parameters such as the beam separation, bunch intensities, number of colliding bunches, and beam size, then it is possible to determine the beam separation if the other parameters are known for both the target luminosity and the measured instantaneous luminosity. From the difference of the two beam separations, different step sizes spanning from 0.5 ${\sigma }$ down to 0.025 ${\sigma }$ are calculated and transmitted to LHC that accordingly steers the beams until the instantaneous luminosity smoothly reaches the target within ± 5%. In this note, the results achieved with the new beam-leveling procedure over almost a year of operation, as well as comparisons with simulations, are presented.

Characterization of Highly Irradiated ALPIDE Silicon Sensors

The ALICE (A Large Ion Collider Experiment) experiment at CERN will upgrade its Inner Tracking System (ITS) detector. The new ITS will consist of seven coaxial cylindrical layers of ALPIDE silicon sensors which are based on Monolithic Active Pixel Sensor (MAPS) technology. We have studied the radiation hardness of ALPIDE sensors using a 30 MeV proton beam provided by the cyclotron U-120M of the Nuclear Physics Institute of the Czech Academy of Sciences in Řež. In this paper, these long-term measurements will be described. After being irradiated up to the total ionization dose 2.7 Mrad and non-ionizing energy loss 2.7 × 10 13 1 MeV n eq · cm - 2 , ALPIDE sensors fulfill ITS upgrade project technical design requirements in terms of detection efficiency and fake-hit rate.