Particle Identification Detector Research Articles

TOP detector for particle identification at Belle II

The Time-Of-Propagation (TOP) counter is a ring-imaging Cherenkov detector designed to identify the charged hadrons in the barrel region of the Belle II detector. The Belle II experiment collected data delivered by the SuperKEKB accelerator from March 2019 to June 2022. After the first run period (Run1), a long shutdown (LS1) was dedicated to implement several accelerator and detector upgrades. The second collision period (Run2) was started in January 2024. The components of the TOP detector and the performance during the Run1 will be reported and the detector upgrade during LS1 and future upgrades will be described.

Studies on a hadronic calorimeter with MPGD technology for a future Muon Collider experiment

In the context of the European strategy for particle physics, the Multi-TeV Muon Collider has emerged as a compelling alternative for advancing our understanding of the Standard Model, after the full exploitation of the High-Luminosity LHC. The physics programme at the Muon Collider includes precise measurements in the Higgs boson sector and the search for new physics at the TeV scale. Achieving these goals relies on accurate full event reconstruction, including the identification and precise four-momentum estimation of various particles. The Particle Flow (PF) algorithm is one of the most suitable approach for this task, exploiting information from tracking, calorimeter, and muon detectors for particle identification and measurements of their momenta/energies. Tracking detectors measure charged particle momenta, while calorimeters provide energy measurements for photons and neutral hadrons. Therefore, a combination of an exceptional tracking system and high-granularity calorimeters is necessary. However, one of the biggest challenges for a future experiment at the Muon Collider is to discriminate the product of the μμ collisions from the intense beam-induced-background (BIB), due to the unstable nature of muons, whose decay products interact with the detector material. To address this, an innovative hadronic calorimeter (HCAL) based on Micro Pattern Gas Detectors (MPGDs) is proposed. MPGDs offer robust technology for high radiation environments and a high granularity for precise spatial measurements. Dedicated studies are needed to assess and optimize the performance of an MPGD-based HCAL, including the development of medium-scale prototypes for performance measurements. The response of HCAL to incoming particles is examined through Monte Carlo simulations using Geant4, comparing the performance of digital and semi-digital readouts, with energy resolution as the figure of merit. The simulated geometry will be integrated into the Muon Collider software to study its impact on jet reconstruction within the full apparatus and in the presence of BIB. The simulation will be also validated through the test of a small-size calorimeter cell equipped with advanced resistive MPGD technologies, namely resistive MicroMegas, resistive μRWELL and RP-WELL.

Signal shapes in multiwire proportional chamber-based TPCs

A large-volume Time Projection Chamber (TPC) is the main tracking and particle identification (PID) detector of the ALICE experiment at the CERN LHC. PID in the TPC is performed via specific energy-loss measurements (dE/dx), which are derived from the average pulse-height distribution of ionization generated by charged-particle tracks traversing the TPC volume. During Runs 1 and 2, until 2018, the gas amplification stage was based on multiwire proportional chambers (MWPC). Signals from the MWPC show characteristic long negative tails after an initial positive peak due to the long ion drift times in the MWPC amplification region. This so-called ion tail can lead to a significant amplitude loss in subsequently measured signals, especially in the high-multiplicity environment of high-energy Pb-Pb collisions, which results in a degradation of the dE/dx resolution. A detailed study of the signal shapes measured with the ALICE TPC with the Ne-CO2 (90-10) and Ar-CO2 (90-10) gas mixtures is presented, and the results are compared with three-dimensional Garfield simulations. The impact of the ion tail on the PID performance is studied employing the ALICE simulation framework and the feasibility of an offline correction procedure to account for the ion tail is demonstrated.

Performance of modular ring imaging Cherenkov detector for particle identification

A compact modular ring imaging Cherenkov (mRICH) detector has been developed to provide K/π separation over a momentum coverage of 2 to 10 GeV/c, and an e/π separation of up to 2.5 GeV/c within the Electron-Ion Collider Generic R&D Consortium (i.e., eRD14 Collaboration). The mRICH detector consists of an aerogel block, a Fresnel lens, a flat-mirror set, and a photosensor plane. In September 2021, an mRICH beam-test was carried out at Jefferson Laboratory (JLab). In this paper, results from JLab beam test will be presented together with future plans for mRICH R&D activities.

Modular RICH detector development for the future Electron Ion Collider experiment

Excellent particle identification is an essential requirement for the future Electron Ion Collider (EIC) experiment. Particle identification (PID) of the final state hadrons in semi-inclusive deep inelastic scattering allows the measurement of flavor-dependent gluon and quark distributions inside nucleons and nuclei. The EIC PID Consortium (eRD14 Collaboration) was formed in 2015 for identifying and developing PID detectors using ring imaging Cherenkov and ultra-fast time-of-flight techniques for the EIC experiments with broad kinematics coverage. To meet the challenge of limited space in the electron end-cap of EIC experiments, a compact modular ring imaging Cherenkov (mRICH) detector has been developed that provides K/πseparation over a momentum coverage of 2 GeV/cto 10 GeV/c, and an e/πseparation up to 2.5 GeV/cor more. The mRICH detector consists of an aerogel block, a Fresnel lens, photosensor plane and flat mirrors enclosing the sides of the space between the lens and photosensors. The first prototype of this detector was successfully tested at Fermi National Accelerator laboratory in April 2016 for verifying the detector principles. This was followed by a second prototype test in 2018 at FNAL with much improved optical design and photosensor integration, which allowed adaptation of different readout options. In September 2021, the third beam-test was carried at Jefferson Laboratory (JLAB) with the goal of testing the mRICH performance with a precision tracking capability.

Helicity dependent cross sections for the photoproduction of π0π± pairs from quasi-free nucleons

Photoproduction of π0π±-pairs from quasifree nucleons bound in the deuteron has been investigated to study the helicity dependence of this reaction. Measurements with a liquid deuterium target were used to extract the unpolarized cross sections for reactions on protons and neutrons. A deuterated, longitudinally polarized solid-butanol target, together with a circularly polarized photon beam, determined the double polarization observable E. From these results the spin-dependent cross sections σ1/2 and σ3/2, corresponding to the anti-parallel and parallel spin configurations of the beam photon and target nucleon, have been derived. The measurements were performed at the Mainz MAMI accelerator with tagged, circularly-polarized photon beams produced via bremsstrahlung from longitudinally polarized electron beams. The reaction products were detected with an almost 4π solid-angle covering calorimeter composed of the Crystal Ball and TAPS detectors, supplemented by plastic scintillation detectors for charged particle identification. The results are sensitive to sequential decays of nucleon resonances via intermediate states and also to the decay of nucleon resonances by emission of charged ρ mesons, and are compared to recent model results.

MCP-PMT quantum efficiency monitoring and operation status of the TOP counter at the Belle II experiment

The Belle II experiment is a high luminosity electron and positron collider experiment at SuperKEKB in Japan. The Time-Of-Propagation counter is a detector for particle identification in the barrel region. Micro-channel-plate photomultipliers are used as photodetectors and measure photon timing with a resolution of 30 ps; this leads to excellent particle identification performance. One of the issues is the photocathode lifetime of the photomultiplier tubes. Monitoring tools have been developed to measure the tube gain, accumulated output charge density and quantum efficiency during physics data taking. The gain was seen to decrease by about 10%. Although the accumulated output charge density is small compared to the tube expected lifetime, a quantum efficiency degradation was found larger than expected for 5% of the tubes after threshold efficiency calibration. Several causes for this degradation are being investigated. They can possibly be related to tube production and noise from the read-out system.

Electron-beam calibration of aerogel tiles for the HELIX RICH detector

The HELIX cosmic-ray detector is a balloon-borne instrument designed to measure the flux of light isotopes in the energy range from 0.2 GeV/n to beyond 3 GeV/n. It will rely on a ring-imaging Cherenkov (RICH) detector for particle identification at energies greater than 1 GeV/n and will use aerogel tiles with refractive index near 1.15 as the radiator. To achieve the performance goals of the experiment it is necessary to know the refractive index and its position dependence over the lateral extent of the tiles to a precision of O(10−4). In this paper we describe the apparatus and methods developed to calibrate the HELIX tiles in an electron beam, in order to meet this requirement.

Recent progress in the construction of KoBRA for low-energy nuclear physics experiments

A multi-purpose experimental instrument, called as KoBRA (Korea Broad acceptance Recoil spectrometer and Apparatus), has been constructed for low-energy nuclear physics experiments at RAON (Rare Isotope Accelerator complex for ON-line experiments), and is being prepared in order to produce rare isotope beams at an energy of about 20 MeV/nucleon during the first beam commissioning phase. A test was performed to measure the positions of 4He ions at the dispersive and achromatic foci of KoBRA using an 241Am α-source placed at the production target position, so as to examine the momentum dispersion and ion beam transport. We report on the results of the test and the detailed design of KoBRA including ion optics, together with the status of detectors for particle identification of rare isotopes.

Current status of In-flight fragment separator for RAON

The in-flight fragment (IF) separator of RAON, the main device for producing rare isotope (RI) beams for nuclear science research and applications, is under development. The IF separator consists of a target, beam dump, magnets, and detector systems. The high-power target and beam dump for the 80 kW primary beam were fabricated using graphite. The IF magnet system consists of a total of 8 dipole magnets, 15 sets of quadrupole magnet triplet, 2 sextupole magnets, and power supply systems. In the high radiation region near the target and beam dump, warm iron high temperature superconducting (HTS) magnets and radiation-resistive dipole magnet are used. In the other region, cold iron low temperature superconducting (LTS) quadrupole magnet triplets and normal conducting (NC) dipole and sextupole magnets are used. Fabrication of all IF magnets have been completed and on-site installation is in progress. Also, detectors for particle identification (PID) and data acquisition (DAQ) systems are currently being installed at the focal planes of the IF separator. The current status of IF separator is briefly introduced.

Study of hybrid micropattern gaseous detector with CsI photocathode for Super Tau-Charm facility RICH

Super τ-Charm facility (STCF) is a future electron-positron collider operating in the τ-Charm energy region with the aim of studying hadron structure and spectroscopy. The baseline design of the STCF barrel particle identification (PID) detector, which covers momentum up to 2 GeV/c, is provided by a Ring Imaging Cherenkov Counter (RICH). The RICH features an approximately focusing design with liquid perfluorohexane sealed in a quartz container as the radiator and a hybrid combination of CsI-coated THGEMs and Micromegas as the photo-electron detector. A 16×16 cm2 prototype with a quartz radiator has been built and tested at DESY and stably operated with an effective gain of 105. In this paper, the design, performance, and reconstruction algorithm of RICH detectors are discussed.

New measurement of double- β decays of Mo100 to excited states of Ru100 with the CUPID-Mo experiment

The CUPID-Mo experiment, located at the Laboratoire Souterrain de Modane (France), was a demonstrator experiment for CUPID. It consisted of an array of 20Li2Mo100O4 (LMO) calorimeters, each equipped with a Ge light detector for particle identification. In this work, we present the result of a search for two-neutrino and neutrinoless double-β decays of Mo100 to the first 0+ and 2+ excited states of Ru100 using the full CUPID-Mo exposure (2.71kgyr of LMO). We measure the half-life of 2νββ decay to the 01+ state as T1/22ν→01+=(7.5±0.8(stat.)−0.3+0.4(syst.))×1020yr. The bolometric technique enables measurement of the electron energies as well as the γ rays from nuclear deexcitation and this allows us to set new limits on the two-neutrino decay to the 21+ state of T1/22ν→21+>4.4×1021yr(90% c.i.) and on the neutrinoless modes of T1/20ν→21+>2.1×1023yr(90% c.i.), T1/20ν→01+>1.2×1023yr(90% c.i.). Information on the electrons' spectral shape is obtained, which allows us to make the first comparison of the single and higher state dominance 2νββ decay models for the 01+ excited state of Ru100.8 MoreReceived 1 August 2022Accepted 2 December 2022DOI:https://doi.org/10.1103/PhysRevC.107.025503©2023 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasDouble beta decayNeutrinoless double beta decayNuclear structure & decaysPhysical SystemsMajorana neutrinosNeutrinosProperties90 ≤ A ≤ 149Nuclear Physics

Study of nanodiamond photocathodes for MPGD-based detectors of single photons

The proposed new Electron–Ion Collider poses a technical and intellectual challenge for the detector design to accommodate the long-term diverse physics goals envisaged by the program. This requires a 4π detector system capable of reconstructing the energy and momentum of final state particles with high precision. The Electron-Ion Collider also requires identification of particles of different masses over a wide momentum range.A diverse spectrum of Particle IDentification detectors has been proposed. Of the four types of detectors for hadron identification, three are based on Ring Imaging Cherenkov Counter technologies, and one is realized by the Time of Flight method. The quest for a novel photocathode, sensitive in the far vacuum ultraviolet wavelength range and more robust than cesium iodide, motivated an R&D programme to explore nano-diamond (ND) based photocathodes, started by a collaboration between INFN and CNR Bari and INFN Trieste. Systematic measurements of the photoemission in different Ar:CH4 and Ar:CO2 gas mixtures with various types of ND powders and Hydrogenated ND (H-ND) powders are reported. A first study of the response of THGEMs coated with different photocathode materials is presented.The progress of this R&D programme and the results obtained so far by these exploratory studies are described.

Time of flight detector for charged particle identification based on circular electron-positron collider

The circular electron-positron collider (CEPC) requires a 3% precision in the measurement of d<i>E</i>/d<i>x</i> to identify long-lived charged particles. However, the measurement of d<i>E</i>/d<i>x</i> has a blind area for each of charged particles of <inline-formula><tex-math id="M8">\begin{document}$\pi / \rm{K}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20222271_M8.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20222271_M8.png"/></alternatives></inline-formula>, <inline-formula><tex-math id="M9">\begin{document}$\pi / \rm{P}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20222271_M9.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20222271_M9.png"/></alternatives></inline-formula>, and <inline-formula><tex-math id="M10">\begin{document}$\rm{K} / \rm{P}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20222271_M10.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20222271_M10.png"/></alternatives></inline-formula>, having transverse momenta of 1 GeV/<i>c</i>, 1.6 GeV/<i>c</i>, and 2 GeV/<i>c</i> respectively. One potential solution is to use a high-precision time-of-flight (TOF) detector with a time resolution of less than 50 ps to fill in the blind area. To address this, we propose a small particle TOF detector that uses small plastic scintillators (<inline-formula><tex-math id="M11">\begin{document}$1 \;\; \mathrm{cm} \times 1 \;\; \mathrm{cm} \times 0.3 \;\; \mathrm{cm}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20222271_M11.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20222271_M11.png"/></alternatives></inline-formula>) silicon photomultipliers for readout. In this work, we introduce the construction of the detector and calibrate its performance by using <inline-formula><tex-math id="M12">\begin{document}${ }^{90} \mathrm{Sr} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20222271_M12.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20222271_M12.png"/></alternatives></inline-formula> electron collimators and high-speed waveform acquisition electronics. Using a constant fraction timing method, we find that the time resolution of the detector is about 48 ps, satisfying the CEPC’s requirements for TOF detection.

Measuring time with high precision in particle physics

Time measurements with sub-nanosecond time resolution (aiming at values of few picoseconds) are of paramount importance for a wide variety of applications. In the field of particle physics, measuring with increasing precision the time taken by a particle to travel between two points (Time-of-Flight, ToF) gives information on the particle’ (relativistic) velocity, contributing to identifying the type of particle (Particle Identification Detectors, PID). Among this category of detectors are also Cherenkov counters, based on the emission of light when a charged particle travels in a transparent medium with a velocity exceeding the light velocity in that medium. Here we discuss a special category of ToF counters using the properties of Cherenkov light to determine the passage of the particles through the detectors with unprecedented precision. Results obtained with test beams are described and analysed, demonstrating the excellent timing resolution that can be obtained. Such detectors may be used to provide a ‘precision time reference’ for calibrating other types of timing detectors. Other applications are, for instance, time-tagging of ‘pile-up’ events in high-luminosity Large Hadron Collider (LHC), and identification of events with anomalous timing properties (for instance, long-lived particles, LLP).

Design and construction of a novel energy-loss optical scintillation system (ELOSS) for heavy-ion particle identification.

We present the development of a novel heavy-ion particle-identification (PID) device based on an energy-loss measurement to be implemented in the focal plane of the S800 spectrograph of the Facility for Rare Isotope Beams (FRIB). The new instrument consists of a multi-segmented optical detector [energy-loss optical scintillation system (ELOSS)] that is filled with xenon at pressures ranging from 400 to 800 Torr. The gas volume is surrounded by arrays of photomultiplier tubes and placed along the direction of the beam for recording the prompt scintillation light. The number of detected photons, which is proportional to the energy deposited by the beam particle along its track in the detector volume, allows one to identify the corresponding atomic number (Z). The ELOSS technology is expected to provide high-resolution ΔE measurements (≤0.6% σ) at a high counting rate (>50kHz). In addition, it has the capability of providing timing information with around 150ps resolution (σ) compared to the lack of useable timing information of the conventional ionization chamber relying on drifting charges. The development of fast, accurate ΔE measurement techniques for present and future nuclear science facilities will have a high impact on the design and implementation of rare-isotope beam experiments at FRIB and their scientific outcome. As such, ELOSS also represents a prototype for the development of PID detector systems of other planned and future spectrometers, such as the high rigidity spectrometer at FRIB.

Track Reconstruction in a High-Density Environment with ALICE

ALICE is the dedicated heavy-ion experiment at the CERN Large Hadron Collider (LHC). Its main tracking and particle-identification detector is a large volume Time Projection Chamber (TPC). The TPC has been designed to perform well in the high-track density environment created in high-energy heavy-ion collisions. In this proceeding, we describe the track reconstruction procedure in ALICE. In particular, we focus on the two main challenges that were faced during the Run 2 data-taking period (2015–2018) of the LHC, which were the baseline fluctuations and the local space charge distortions in the TPC. We present the corresponding solutions in detail and describe the software tools that allowed us to circumvent these challenges.

High-Resolution Imager Based on Time-to-Space Conversion

We present an high-resolution 3D (X,Y,t) imager for time-resolved experiments based on time-to-space conversion. The system uses Cross Delay-Line detectors (CDL) for particle identification and a fully-configurable digital processor based on Field Programmable Gate Arrays (FPGAs) for the 3D image reconstruction. The instrument reaches a spatial resolution of 45 μm FWHM (i.e.,18 μm r.m.s.) and a temporal precision of 15 ps r.m.s.. The detection rate achieved is 10 Mcps, with a dead-time below 7 ns, leading to a global throughput up to 6 Gb/s. In addition to the state-of-the-art performance, the innovative aspect of the presented contribution resides in the complete reconfigurability of the instrument: it is, in fact, the first time that the Time-to-Digital Converter (TDC) used for the time-to-space conversion, has been fully implemented in programmable logic, without the use of dedicated Application Specific Integrated Circuit (ASIC) components. This advancement allows to adapt the instrument to the experimental setup without undergoing impractical hardware modifications.

DIRC-like time-of-flight detector for the experiment at the Super Tau-Charm Facility

The Super Tau-Charm Facility (STCF) is a future electron-positron collider proposed in China with a peak luminosity of above 0.5 × 1035 cm-2s-1 and center-of-mass energy ranging from 2 to 7 GeV. An excellent particle identification (PID) capability is one of the most important requirements for the detector at the STCF. A 3σ π/K separation power at the momentum of up to 2 GeV/c is required within the detector acceptance. A DIRC-like time-of-flight (DTOF) detector is proposed to meet the PID requirement for the endcap region of the STCF. The conceptual design of the DTOF detector and its geometry optimization is herein presented. The PID performance of the detector is studied using Geant4 simulation. With a proper reconstruction algorithm, an overall time resolution of ∼50 ps is achieved for the detector with an optimum geometry when convoluting contributions from all other sources, including the transit time spread (TTS) of the photodetector, electronic timing accuracy, and an assumed precision (∼40 ps) of the event start time. A π/K separation power of better than 4σ at the momentum of 2 GeV/c is achieved over the entire sensitive area of the DTOF detector, thereby fulfilling the physics requirement of the PID detector for the experiment at the STCF.

Design of the barrel and endcap DIRC detectors for particle identification in PANDA

The PANDA experiment at the future Facility for Antiproton and Ion Research (FAIR) in Darmstadt/Germany aims to investigate fundamental questions of hadron physics. PANDA is designed as a fixed-target experiment for an antiproton beam with a momentum range of 1.5 GeV/[Formula: see text] to 15 GeV/[Formula: see text]. In order to obtain an excellent particle identification of pions and kaons, two independent DIRC detectors have been developed for two adjacent spatial regions. The Barrel DIRC covers polar angles from [Formula: see text]–[Formula: see text] and performs [Formula: see text] separation with [Formula: see text] or more for momenta from 0.5 to 3.5 GeV/[Formula: see text]. The novel Endcap Disc DIRC (EDD) detector will cover the forward polar angles between [Formula: see text] and [Formula: see text] and will provide a [Formula: see text] separation from 0.5 GeV/[Formula: see text] up to 4 GeV/[Formula: see text] with a separation power at least [Formula: see text]. The design of the Barrel DIRC is based on the successful BaBar DIRC and the SuperB FDIRC R&D with several improvements to optimize the performance for PANDA. Both PANDA DIRC detectors use synthetic fused silica as material for radiators and light guides and lifetime-enhance Microchannel Plate PMTs (MCP-PMTs) as sensors. The Barrel DIRC uses narrow bars as a radiator, a prism-shaped expansion volume and a complex multi-layer spherical lens as focusing system. The Cherenkov radiator for the EDD is a large, 2 cm thick fused silica plate that is divided into four identical quadrants. A combination of bars and cylindrical elements with aluminum coating focus the Cherenkov light on the MCP-PMTs with segmented anode plates. The technical design of the two DIRC detectors and the performance of prototypes, tested in a mixed hadron beam at CERN, will be discussed.