High Momentum Particle Identification Detector Research Articles

PID performance of the High Momentum Particle IDentification (HMPID) detector during LHC-Run 2

Abstract The ALICE apparatus is devoted collecting proton–proton (pp), proton–nucleus (p–A) and nucleus–nucleus (A–A) collision data provided by the LHC, to study the properties of strongly interacting matter under extremely high temperature and energy density conditions. In ALICE, the momentum of a track is evaluated by exploiting a solenoid magnetic field of 0.5 T. Among the ALICE PID detectors, the HMPID (High Momentum Particle Identification Detector) is devoted to the identification of charged hadrons . It consists of seven identical RICH (Ring Imaging Cherenkov) counters, with liquid C 6 F14 as Cherenkov radiator (n ≈ 1.298 at λ ph = 175 nm). Cherenkov photons and charged particles are detected by a MWPC (Multi Wire Proportional Chamber), equipped with a pad-segmented CsI coated photo-cathode. The HMPID provides 3 σ K– π and p–K separation up to p T = 3 and 5 GeV/ c , respectively. The detector performance depends on the experimental conditions, such as the event multiplicity and the intensity of the solenoid magnetic field. During the LHC Run 2 data-taking period (2015–2017), the HMPID collected data from different colliding systems with a magnetic field intensity B = 0.5 T and pp data with B = 0.2 T were also recorded. A review of the detector PID performance during the LHC Run 2 data-taking period will be shown. The contribution provided, so far, by the HMPID to the ALICE physics measurements, performed with the LHC Run 2 data, will also be presented.

Preparing the ALICE-HMPID RICH for the high-luminosity LHC period 2021–2023

Abstract Approaching successfully the end of the LHC Run2 period (2015–2018), the RICH based High Momentum Particle IDentification detector (HMPID) prepares for the High Luminosity LHC (HL-LHC) Run 3 period (2020–2023) where the collider will provide up to 50 kHz of Pb-Pb collision rate at s NN = 5 TeV. The upgraded ALICE detector will be able to read out all interactions and it will exploit the fully scientific potential of the HL-LHC to study the properties of the Quark–Gluon Plasma phase (QGP), using proton–proton, nucleus–nucleus and proton–nucleus collisions at high energies. The ALICE continuous detector read out will ensure the Online/Offline (O 2 ) identification of rare trigger topologies and an effective data compression factor. This paper presents the HMPID status and the activities under way to integrate the detector in the new ALICE O2 Trigger environments. The stable performance of the detector, the stability of the Multi-Wire Proportional Chamber (MWPC) during preliminary tests of high luminosity conditions in ALICE using pp collisions, and the progressing upgrading activities, support the participation of the HMPID in the ALICE scientific program defined for the HL-LHC period.

The High Momentum Particle IDentification (HMPID) detector PID performance and its contribution to the ALICE physics program

The ALICE apparatus is dedicated to study the properties of strongly interacting matter under extremely high temperature and energy density conditions. For this, enhanced particle identification (PID) capabilities are required. Among the PID ALICE detectors, the ALICE-HMPID (High Momentum Particle IDentification) detector is devoted to the identification of charged hadrons, exploiting the Cherenkov effect. It consists of seven identical RICH modules, with liquid C6F14 as Cherenkov radiator (n ≈1.298 at λ=175nm). Photon and charged particle detection is performed by a MWPC, coupled with a pad segmented CsI coated photo-cathode. The total CsI active area is 10.3m2. The HMPID provides 3 sigma separation for pions and kaons up to pT=3GeV/c and for kaons and (anti-)protons up to pT=5GeV/c. A review of the HMPID PID performance, in particular in the challenging central Pb–Pb collisions, and its contribution to the ALICE physics program, using the LHC RUN1 (2010–2013) and RUN2 (2015) data, are presented.

Performance of the High Momentum Particle IDentification detector of ALICE during the LHC run period 2015–2016

In the period June 2015–September 2016 the LHC has delivered pp and Pb-Pb collisions respectively at √s=13TeV and √sNN=5.02TeV for a total integrated luminosity in ALICE of 14pb−1. The High Momentum Particle IDentification detector (HMPID) is part of the ALICE experiment. It is based on seven Ring Imaging Cherenkov (RICH) modules, 1.3×1.3m2 each, with a proximity focusing geometry. The Cherenkov photon detection is achieved by pad segmented photocathodes, coated with 300nm thick Caesium Iodide layer, installed in multiwire proportional chambers. Liquid C6F14 (perfluorohexane) with n=1.2989 at λ=175nm is used as Cherenkov radiator. The HMPID identifies with three sigma separation charged π and K in the momentum range 1–3GeV/c and protons in the range 1.5–5GeV/c. The scatter plots of the Cherenkov angle for both pp and Pb-Pb events are presented as preliminary Particle Identification (PID) performance. After the good results shown during 2010–2013, in this paper the HMPID performance in the period 2015–2016, with emphasis on the CsI quantum efficiency stability, are presented. Finally the perspectives of the detector operation in the period HL-LHC 2019–2022, are briefly discussed.

The ALICE–HMPID performance during the LHC run period 2010–2013

The ALICE–High Momentum Particle Identification Detector (HMPID) is based on seven modules of proximity focusing Ring Imaging Cherenkov detectors. It is equipped with CsI photo-cathodes for the Cherenkov photon detection installed in multiwire proportional chambers filled with methane. It uses liquid C6F14 as Cherenkov radiator and identifies with three sigma separation, charged π and K in the momentum range 1–3GeV/c, and protons in the range 1.5–5GeV/c.At the end of the first run period 2010–2013 of the Large Hadron Collider, the HMPID performance is analysed. No ageing effects of CsI photo-cathodes induced by the ion avalanches have been observed, and we do not expect to reach the charge threshold during the High Luminosity LHC run period 2019–2021.Leakages of C6F14 in 4 out of 21 quartz radiator vessels, combined with 3 HV failing sectors out of 42, have limited the full detector acceptance to 72%. Improvements on the filling operation of the vessels should minimize further leakage. Finally, the particle identification performances are introduced using p-Pb collisions. For Pb–Pb central collisions, where purity and contamination of identified particles are extracted via a Monte Carlo simulation, the impact of the background on the pattern recognition algorithm is briefly discussed.

A very high momentum particle identification detector

The construction of a new detector is proposed to extend the capabilities of ALICE in the high transverse momentum (pT) region. This Very High Momentum Particle Identification Detector (VHMPID) performs charged hadron identification on a track-by-track basis in the 5 GeV/c < p < 25 GeV/c momentum range and provides ALICE with new opportunities to study parton-medium interactions at LHC energies. The VHMPID covers up to 30% of the ALICE central barrel and presents sufficient acceptance for triggered- and tagged-jet studies, allowing for the first time identified charged hadron measurements in jets. This Letter of Intent summarizes the physics motivations for such a detector as well as its layout and integration into ALICE.

R&D on high momentum particle identification with a pressurized Cherenkov radiator

We report on the R&D results for a Very High Momentum Particle Identification (VHMPID) detector, which was proposed to extend the charged hadron track-by-track identification in the momentum range from 5 to 25GeV/c in the ALICE experiment at CERN. It is a RICH detector with focusing geometry using pressurized perfluorobutane (C4F8O) as a Cherenkov radiator. A MWPC with a CsI photocathode was investigated as the baseline option for the photon detector. The results of beam tests performed on RICH prototypes using both liquid C6F14 radiator (in proximity focusing geometry for reference measurements) and pressurized C4F8O gaseous radiator will be shown in this paper. In addition, we present studies of a CsI based gaseous photon detector equipped with a MWPC having an adjustable anode–cathode gap, aiming at the optimization of the chamber layout and performance in the detection of single photoelectrons.

A Very High Momentum Particle Identification Detector for the ALICE Experiment at the LHC

The purpose of the ALICE experiment is the study of the quark-gluon plasma (QGP) in heavy ion collisions at LHC. To this end ALICE has unique PID capability to identify a wide variety of particles in the low to intermediate momentum range. We propose to enhance these capabilities with the Very High Momentum Particle Identification Detector (VHMPID), improving the identification of charged pions, kaons, protons and anti-protons in the momentum range 5 < p < 25 GeV/c on a track-by-track basis. This upgrade provides ALICE with new opportunities to study parton-medium interactions. The underlying physics and the relevant degrees of freedom in the QGP are not known. Only specific experimental evidence of the modification of the harmonization process in medium will enable us to gain a deeper understanding of the fundamental process of hadron formation during the evolution of the deconfined matter. Since the low momentum region of the hadron spectrum is populated by many competing processes, only the high momentum part of the spectrum can be interpreted unambiguously. The VHMPID is a Focusing Ring Imaging Cerenkov with C4F10 gaseous radiator coupled to a Csl-based photon detector. The VHMPID presents sufficient acceptance for triggered- and tagged-jet studies, allowing for the first time, identified charged hadron measurements in jets.

The Cherenkov radiator system of the high momentum particle identification detector of the ALICE experiment at CERN-LHC

The aim of this paper is to present the design, the implementation and the operational modes of the Liquid Circulation System (LCS) built to circulate, purify and monitor the liquid perfluorohexane (C 6F 14) in the ALICE HMPID. The HMPID RICH uses C 6F 14 as Cherenkov radiator medium circulating in 21 quartz trays. LCS features a pressure-regulated closed circuit, ensuring the C 6F 14 highest transparency to ultraviolet light. Intrinsically safe working conditions are obtained, thanks to a novel liquid distribution “cascade” system. Moreover the system is protected against anomalous working conditions by a dedicated Control System, which operates it in both automatic and manual mode, locally and remotely, safeguarding the quartz radiator vessels.

The ALICE-HMPID Detector Control System: Its evolution towards an expert and adaptive system

The High Momentum Particle IDentification (HMPID) detector is a proximity focusing Ring Imaging Cherenkov (RICH) for charged hadron identification. The HMPID is based on liquid C 6F 14 as the radiator medium and on a 10 m 2 CsI coated, pad segmented photocathode of MWPCs for UV Cherenkov photon detection. To ensure full remote control, the HMPID is equipped with a detector control system (DCS) responding to industrial standards for robustness and reliability. It has been implemented using PVSS as Slow Control And Data Acquisition (SCADA) environment, Programmable Logic Controller as control devices and Finite State Machines for modular and automatic command execution. In the perspective of reducing human presence at the experiment site, this paper focuses on DCS evolution towards an expert and adaptive control system, providing, respectively, automatic error recovery and stable detector performance. HAL9000, the first prototype of the HMPID expert system, is then presented. Finally an analysis of the possible application of the adaptive features is provided.

R&D results on a CsI-coated triple thick GEM-based photodetector

The very high momentum particle identification detector proposed for the ALICE upgrade is a focusing RICH using a C 4F 10 gaseous radiator. For the detection of Cherenkov photons, one of the options currently under investigation is to use a CsI-coated triple thick GEM with metallic or resistive electrodes. We will present results from the laboratory studies as well as preliminary results of beam tests of a RICH detector prototype consisting of a CaF 2 radiator coupled to a 10×10 cm 2 CsI-coated triple thick GEM equipped with a pad readout and GASSIPLEX-based front-end electronics. With such a prototype the detection of Cherenkov photons simultaneously with minimum ionizing particles has been achieved for the first time in a stable operation mode.

Results from cosmics and first LHC beam with the ALICE HMPID detector

The ALICE HMPID (High Momentum Particle IDentification) detector has been designed to identify charged pions and kaons in the range 1 ÷ 3 GeV/c and protons in the range 1.5 ÷ 5 GeV/c . It consists of seven identical proximity focusing RICH (Ring Imaging Cherenkov) counters, covering in total 11 m 2, which exploit large area MWPC equipped with CsI photocathodes for Cherenkov light imaging emitted in a liquid C 6F 14 radiator. The ALICE detector has been widely commissioned using cosmics and LHC beam from December 2007 until October 2008. During the cosmics data taking the HMPID detector collected a large set of data, using mainly the trigger provided by the TOF detector. We present here preliminary results of detector alignment using TPC tracking. The HMPID could be operated in a stable way, at a safe HV setting, also during LHC beam injection and circulation tests, when a very large occupancy (up to 50%) was achieved. Resulting gain mapping and overall detector performance will also be discussed.

The ALICE HMPID detector ready for collisions at the LHC

ALICE has been specifically optimized to study heavy-ion collisions at the LHC, up to a charged particle density of 8000 per unit of rapidity in central heavy-ion collisions at s NN = 5.5 TeV . The High Momentum Particle Identification Detector (HMPID) has a proximity focusing geometry with a liquid C 6F 14 Cherenkov radiator coupled to Multi-Wire Pad Chambers (MWPC) equipped with CsI photocathodes, over a total active area of 11 m 2 . It has been designed to identify charged pions and kaons in the range 1 ⩽ p ⩽ 3 Gev / c and protons in the range 2 ⩽ p ⩽ 5 Gev / c . The as-built detector and all relevant subsystems (gas, liquid C 6F 14, cooling and control) are described. Installation issues and first commissioning results are also presented.

Pattern recognition techniques of charged hadron identification with HMPID at LHC

The High Momentum Particle Identification Detector (HMPID), already installed in the ALICE setup at LHC, is ready to identify charged hadrons with momentum up to 5 GeV/ c. It consists of seven modules of a RICH detector with a CsI photocathode. The HMPID will operate to identify charged hadrons both in Pb–Pb collisions and in p–p collisions. The strategy to identify charged hadrons will differ according to the colliding system. In the case of central Pb–Pb collisions, the identification of Cherenkov photons requires efficient pattern recognition algorithm (based on a modified Hough transform, that maps the pad coordinate space directly to the Cherenkov angle parameter space). In the first p–p collisions, instead, where the tracking has to be optimized (or even missing, as sometimes in the cosmic runs), a first reconstruction step based on a new algorithm (Hidden Track Algorithm—HTA) will be used. The tracking parameters are not used in the pattern recognition, at the end an estimate of the track direction as well as the mean 〈 θ C 〉 will be performed. The HTA will be here described and preliminary results on its performances will be presented.

The High Momentum Particle Identification Detector in ALICE at LHC

The ALICE High Momentum Particle Identification Detector (HMPID) is a proximity focusing ring imaging Cherenkov (RICH) for the hadron discrimination at high transverse momenta ( 1 < p t < 3 GeV/c for π and k, 1 < p t < 5 GeV/c for p). This paper focus on the HMPID particle identification (PID) capabilities in the expected charged particle occupancy dN ch / d η = 6000 , simulated in central Pb-Pb ALICE events.

Experience from the construction and installation of the HMPID CsI-RICH detector in ALICE

The construction and installation phases of the High Momentum Particle IDentification (HMPID) detector of the ALICE experiment were completed by summer 2006. The total active area of the detector is 11 m 2 . It represents the largest scale application of CsI photo-cathodes in RICH detectors to date. We will report on the production of the CsI photo-cathodes, the readout electronics, the Multi-wire Proportional Chambers (MWPCs) and the assembly and handling procedures needed to produce such a large detector.

The current progress of the ALICE Ring Imaging Cherenkov Detector

Recently, the last two modules (out of seven) of the ALICE High Momentum Particle Identification Detector (HMPID) were assembled and tested. The full detector, after a pre-commissioning phase, has been installed in the experimental area, inside the ALICE solenoid, at the end of September 2006. In this paper, we review the status of the ALICE/HMPID project and we present a summary of the series production of the CsI photo-cathodes. We describe the key features of the production procedure which ensures high-quality photo-cathodes as well as the results of the quality assessment performed by means of a specially developed 2D scanner system able to produce a detailed map of the CsI photo-current over the entire photo-cathode surface. Finally, we present our recent R&D efforts toward the development of a novel generation of imaging Cherenkov detectors with the aim to identify, in heavy-ion collisions, hadrons up to 30 GeV/ c.

Performance of the high momentum particle identification CsI-RICH for ALICE at CERN-LHC

The ALICE High Momentum Particle Identification (HMPID) detector consists of an array of seven identical proximity focusing Ring Imaging Cherenkov counters. It has been designed to identify charged pions and kaons in the range 1 < p t < 3 GeV / c and protons in the range 2 < p t < 5 GeV / c . The total active area of this detector is about 11 m 2 and represents the largest scale application of CsI photocathodes to date. The detector performance, as being evaluated in test beam at CERN, will be discussed for the first five modules.

Status of the HMPID CsI-RICH project for ALICE at the CERN/LHC

The ALICE (A Large Ion Collider Experiment) high momentum particle identification (HMPID) detector, presently under construction, consists of seven identical proximity focusing ring imaging Cherenkov (RICH) counters exploiting large area CsI photocathodes for Cherenkov light imaging. With a total area of 11 m/sup 2/, it represents the largest CsI-RICH system ever used in High Energy Physics. The detector layout, assembly and quality checks will be presented, with particular emphasis on CsI photocathodes mass production. A validation procedure has been established combining the results of the photocathode response mapping obtained in a dedicated VUV scanner with test beam data. The long-term stability has also been studied by irradiation with a Sr-90 source of a final size CsI photocathode inside a detector prototype.

The pattern recognition method for the CsI-RICH detector in ALICE

Abstract The High Momentum Particle Identification Detector in the ALICE experiment is based on a Ring Imaging Cherenkov (RICH) detector with a CsI photocathode. The identification of Cherenkov photons, especially in conditions of high occupancy as will be the case in Pb–Pb collisions at the Large Hadron Collider, requires efficient pattern recognition algorithms. The results of an algorithm based on the Hough transform, that maps the pad coordinate space directly to the Cherenkov angle parameter space, will be shown. The performance of the method on real events collected in the STAR experiment at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven (USA), where a prototype of the RICH detector developed in the ALICE framework has been successfully operated, will also be described.