Particle Identification Device Research Articles

The TOP counter and determination of bunch-crossing time at Belle II

At the Belle II experiment a Time-of-Propagation (TOP) counter is used for particle identification in the barrel region. This novel type of particle identification device combines the Cherenkov ring imaging technique with the time-of-flight and therefore it relies on a precise knowledge of the time of collision in each triggered event. We discuss the performance of the counter and present a maximum likelihood based method for the determination of event collision time from the measured data.

Performance evaluation of the aerogel RICH counter for the Belle II spectrometer using early beam collision data

Abstract The Aerogel Ring Imaging Cherenkov (ARICH) counter serves as a particle identification device in the forward end-cap region of the Belle II spectrometer. It is capable of identifying pions and kaons with momenta up to $4\>$GeV$\>$c$^{-1}$ by detecting Cherenkov photons emitted in the silica aerogel radiator. After the detector alignment and calibration of the probability density function, we evaluate the performance of the ARICH counter using early beam collision data. Event samples of $D^{\ast +} \to D^0 \pi^+ (D^0 \to K^-\pi^+)$ were used to determine the $\pi(K)$ efficiency and the $K(\pi)$ misidentification probability. We found that the ARICH counter is capable of separating kaons from pions with an identification efficiency of $93.5 \pm 0.6 \, \%$ at a pion misidentification probability of $10.9 \pm 0.9 \, \%$. This paper describes the identification method of the counter and the evaluation of the performance during its early operation.

Operational status of the Belle II Time-Of-Propagation counter readout and data acquisition system

Abstract The front-end electronics system for the Belle II Time-Of-Propagation (TOP) counter was fully installed in May 2016. The detector is a novel particle identification device for the barrel region, where Cherenkov ring images are reconstructed with precise timing information of each photon. The readout electronics need to have excellent timing performance for single photon detection. To exploit the benefit of high luminosity, the electronics must also be able to cope with a high input trigger rate (30 kHz) and have buffer memory which is deep enough to wait for a trigger decision ( > 5 μ s ). The TOP electronics has switching capacitor arrays to sample waveforms with 2.7 GSample/s, which allows a timing resolution of 50 ps for a single photon signal. The programmable logic and the processing system are the effective implementation to meet these requirements, where flexible optimization and step-by-step development of readout logic are possible. The system has been successfully operated in the first accelerator commissioning runs with beam collisions in 2018, where the typical trigger rate was 500 Hz . Operation with a 20 kHz trigger rate was also tested.

Differential correlation measurements with the identity method

We present an extension of the identity method initially introduced for particle yield fluctuation studies towards measurements of differential correlations. The extension is developed and illustrated in the context of measurements of the normalized two-particle cumulant $R_2$ but is adaptable to any correlation measurements, including differential flow measurements. The identity method is also extended to account for an arbitrary number of particle identification devices and signals.

Construction of silica aerogel radiator system for Belle II RICH Counter

We have developed a RICH counter as a new forward particle identification device for the Belle II experiment. As a Cherenkov radiator in this counter, a dual aerogel layer combination consisting of two refractive indicies, n=1.045 and 1.055, is employed. Mass production of these aerogel tiles has been done during 2013–2014 with new method improved by Chiba group. Optical qualities for them have been examined. The refractive indices of the obtained tiles were found to be in good agreement with our expectations, and the transparencies were high enough to be used for the RICH radiator.

Particle Identification at Belle II

We report on the charged particle identification (PID) systems for the upcoming Belle II experiment. The time of propagation counter in the central region and the proximity focusing ring imaging Cherenkov counters with aerogel radiator in the forward region will be used as the PID devices. They are expected to provide a kaon identification efficiency of more than 94% at a low pion misidentification probability of 4%. The motivation for the upgrade, method and status of both systems are discussed.

Particle identification performance of the prototype aerogel RICH counter for the Belle II experiment

We have developed a new type of particle identification device, called an Aerogel Ring Imaging Cherenkov (ARICH) counter, for the Belle II experiment. It uses silica aerogel tiles as Cherenkov radiators. For detection of Cherenkov photons, Hybrid Avalanche Photo-Detectors (HAPDs) are used. The designed HAPD has a high sensitivity to single photons under a strong magnetic field. We have confirmed that the HAPD provides high efficiency for single-photon detection even after exposure to neutron and gamma-ray radiation that exceeds the levels expected in the 10-year Belle II operation. In order to confirm the basic performance of the ARICH counter system, we carried out a beam test at the DESY using a prototype of the ARICH counter with six HAPD modules. The results are in agreement with our expectations and confirm the suitability of the ARICH counter for the Belle II experiment. Based on the in-beam performance of the device, we expect that the identification efficiency at 3.5 GeV/c is 97.4% and 4.9% for pions and kaons, respectively. This paper summarizes the development of the HAPD for the ARICH and the evaluation of the performance of the prototype ARICH counter built with the final design components.

A multiple sampling ionization chamber for the External Target Facility

A multiple sampling ionization chamber used as a particle identification device for high energy heavy ions has been developed for the External Target Facility. The performance of this detector was tested with a 239Pu α source and RI beams. A Z resolution (FWHM) of 0.4–0.6 was achieved for nuclear fragments of 18O at 400AMeV.

Development of the micro-channel plate photomultiplier for the Belle II time-of-propagation counter

The time-of-propagation counter for the Belle II experiment is a new particle identification device using ring imaging Cherenkov technique. In order to detect each Cherenkov photon with a timing precision of 30–40ps in a 1.5T magnetic field, a micro-channel plate photomultiplier tube is a suitable device for the TOP counter. By introducing an atomic layer deposition technique on the micro-channel plate surface, the tube lifetime was improved by a factor of 3–10 relative to more conventional devices. A total of 530 tubes have been produced. To ensure appropriate tube performance, the quantum efficiency, gain and transit time spread have been measured for all units. The results from each measurement are discussed. Results from a beamtest with a 2GeV/c positron beam are also reported and demonstrate the good tube performance.

Performance of the MCP-PMT for the Belle II TOP counter in a magnetic field

The time of propagation (TOP) counter is a novel particle identification device for the Belle II experiment, utilizing the ring imaging Cherenkov technique. It is composed of a 2.7m long quartz bar and 32 micro channel plate photomultiplier tubes (MCP-PMTs) attached on the end of the bar. The MCP-PMT has a typical quantum efficiency of 28%, a photoelectron collection efficiency of about 55%, and a transit time spread (TTS) less than 50ps for single photon detection. Since the TOP counters are installed in the 1.5T magnetic field of the Belle II detector, the MCP-PMTs are required to keep those characteristics with gain of more than 5×105 in the magnetic field. Therefore, we investigated gain, TTS, and single photon detection efficiency of the MCP-PMTs in the magnetic field and found that they satisfy the requirements. We are starting complete inspections for more than 500 MCP-PMTs, and have inspected up to 87 MCP-PMTs.

The time-of-propagation counter for BelleII

The Belle II detector operating at the future upgrade to the KEKB accelerator will perform high-statistics precision investigations into the flavor sector of the Standard Model. As charged hadron identification is a vital element of the experiment's success, the time-of-propagation (TOP) counter has been chosen as the primary particle identification device in the barrel region of Belle II. The TOP counter is a compact variant of the detection of internally reflected Cherenkov light (DIRC) technique and relies heavily on exquisite single photon timing resolution with micro-channel plate photomultiplier tubes. We discuss the general principles of TOP operation and optimization of the Belle II TOP configuration, which is expected to provide 4 sigma or better separation of kaons and pions up to momenta of approximately 4 GeV/ c.

R&D of particle identification devices with high-precision timing

We have studied micro-channel-plate photo-multiplier tubes (MCP-PMT), which realize timing measurements of the single photons with high precision of about 30ps. We investigated the timing properties of 4 different types with a magnetic field, and measured the lifetime of the gain, quantum efficiency and transit time spread.As an application, we studied the timing resolution of TOF counters by means of Cherenkov-light detection with a MCP-PMT, and attained a 6.2ps resolution using 3GeV/c pion-beams with readout electronics of 4.1ps resolution. As another application, we have developed a novel particle identification device, named TOP counter, which is a Cherenkov ring imaging counter with precise timing determination, especially for upgrading B-factory experiments. We performed beam tests with the prototype, and obtained the expected results.

Performances of a GEM-based TPC prototype for new high-rate particle experiments

Time projection chamber (TPC) has been successfully used as a central tracker and a particle identification device in a number of a high-energy physics experiments. However, the performance requirements on TPC for new high-rate particle experiments greatly exceed the abilities of traditional TPC readout by multi-wire proportional chamber (MWPC). Gas Electron Multiplier (GEM) detector has great potential to improve TPC performances when used as amplification device. In this paper we present the R&D activity on a new GEM-based TPC (TPG) detector for the inner part of the AMADEUS experiment, a new experimental proposal at DA Φ NE accelerator at LNF, aiming to perform measurements of the low-energy negative kaons interactions in nuclei. In order to evaluate the TPG feasibility, a 10 × 10 cm 2 prototype with a drift length up to 15 cm are designed. The performances of a 10 × 10 cm 2 pre-existing prototype with a reduced drift gap, operated with Ar / CO 2 / CF 4 (45/15/40) gas mixture and successfully tested at BTF facility, are presented. The gas mixture properties, such as the electron drift velocity and the diffusion, have been measured and they result comparable with those simulated with Garfield. A good resolution along the beam direction ( z-coordinate), sufficient for a more large scale TPG in AMADEUS, is achieved.

Study of a proximity focusing RICH with a silica aerogel radiator

A proximity focusing RICH based on a silica aerogel Cherenkov radiator has been developed for a new particle identification device in the upgraded Belle detector. To further improve the detector performance, a new concept for Cherenkov ring imaging has been introduced, where multiple aerogel layers with different indices are accumulated to increase the number of detected photons without making the Cherenkov photon angle resolution worse. By constructing a prototype counter, this idea was validated in a test beam experiment, and a 5.5 σ π / K separation at 4 GeV / c with more than nine photoelectrons was achieved. We will present new results from a beam test as well as recent improvements on aerogel radiators.

PARTICLE DETECTOR R&D

Recent results on the particle detector R&D for new accelerators are reviewed. Different approaches for the muon systems, hadronic and electromagnetic calorimeters, particle identification devices, and central trackers are discussed. Main emphasis is made on the detectors for the International Linear Collider and Super B-factory. A detailed description of a novel photodetector, a so called Silicon Photomultiplier, and its applications in scintillator detectors is presented.

High-rate particle identification of high-energy heavy ions using a tilted electrode gas ionization chamber

A high-rate particle identification device for high-energy heavy ions has been developed which utilizes a stacked configuration of grid-less parallel plate gas ionization chambers with thin anode–cathode gaps. The high-rate capability of this chamber was realized by adopting bipolar shaping of anode signals and by the suitable choice of a counter gas. Z-resolutions of 0.2–0.3 were obtained for nuclear fragments of Ar 40 at 95 A MeV with an intensity as high as 10 6 cps .

INCLUSIVE CHARGED KAON PRODUCTION FROM B MESONS IN ϒ(4S) DECAYS

We have investigated the inclusive production of charged kaons from B mesons in ϒ (4S) decays. We present our results (up to 800 MeV/c) of the measurement of the charged kaon momentum spectrum, using information from the specific ionization (dE/dx) particle identification (PID) device. We fit PID histograms with known samples of primary (pion, kaon, proton) and secondary (electron, muon) control shape histograms, using a χ2 minimization technique. We compare our findings with ARGUS and with MC and comment on the implications for b → s g from the analsis.

The LHCb experiment

The LHCb experiment is designed to fully exploit the large number of b hadrons expected at the LHC energy and luminosity. The experiment is equipped with particle identification devices and can efficiently trigger events with different B-meson final states, allowing systematic studies of CP violation and other rare phenomena in the b hadron system with a high precision which could reveal physics beyond the Standard Model.

Performance of the photomultiplier tubes used in the DIRC of [formula omitted]:: effect of a magnetic field and of helium

This presentation summarizes the measurements performed on the ETL 9125FLB17 photomultiplier tubes, used in the particle identification device of the high-energy physics BaBar experiment. In particular, we show how the performance of the phototubes is degraded by either a magnetic field or helium gas.

The DIRC counter: a new type of particle identification device for B factories

A very thin, solid radiator, totally internally reflecting, imaging Cherenkov counter (DIRC) is described. This device is well matched to the hadronic charged particle identification requirements at an asymmetric e + e − B factory.