Charged Particle Identification Research Articles

A data-driven [formula omitted] simulation with normalizing flow

In high-energy physics, precise measurements rely on highly reliable detector simulations. Traditionally, these simulations involve incorporating experiment data to model detector responses and fine-tuning them. However, due to the complexity of the experiment data, tuning the simulation can be challenging. One crucial aspect for charged particle identification is the measurement of energy deposition per unit length (referred to as dE/dx). This paper proposes a data-driven dE/dx simulation method using the Normalizing Flow technique, which can learn the dE/dx distribution directly from experiment data. By employing this method, not only can the need for manual tuning of the dE/dx simulation be eliminated, but also high-precision simulation can be achieved.

Effect of large-angle incidence on particle identification performance for light-charged ([formula omitted]) particles by pulse shape analysis with a pad-type nTD silicon detector

In recent years, particle discrimination methods based on digital waveform analysis techniques for neutron-transmutation-doped silicon (nTD-Si) detectors have become widely used for the identification of low-energy charged particles. Although the particle discrimination capability of this method has been well demonstrated for small incident angles, the particle discrimination performance may be affected by changes in the detector response when the detector is moved closer to the charged particle source and the incident position distribution and incident angle distribution to the detector become wide. In this study, we performed a beam test for particle discrimination in light-charged (Z≤2) particles using the digital waveform analysis method with a pad-type nTD-Si detector and investigated the dependence of the performance of the particle discrimination on the incident position and incident angle. As the incident angle increased, a decrease in the maximum current was observed, which was sufficient to affect the performance of the particle discrimination. This decrease can be expressed as a function of the penetration depth of the charged particles into the detector, which varies for each nuclide.

Prototype of a dual-radiator RICH detector for the Electron–Ion Collider

A dual-radiator Ring Imaging Cherenkov (dRICH) will provide charged hadrons particle identification in the hadronic end-cap of a general-purpose experiment at the future Electron–Ion Collider (EIC). We developed a prototype to test the performance and validate the use of Silicon Photo-Multipliers (SiPM), the baseline photo-sensor candidate for the dRICH. They provide a cheap, highly efficient technology and they are not sensitive to the high magnetic field. The general features of the detector, a detailed view of the prototype and its different configurations, the test beam performed, and the preliminary results we obtained are presented.

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.

Optimization of convolutional neural networks for background suppression in the PandaX-III experiment

The tracks recorded by a gaseous detector provide a possibility for charged particle identification. For searching the neutrinoless double beta decay events of 136Xe in the PandaX-III experiment, we optimized the convolutional neural network based on the Monte Carlo simulation data to improve the signal-background discrimination power. EfficientNet is chosen as the baseline model and the optimization is performed by tuning the hyperparameters. In particular, the maximum discrimination power is achieved by optimizing the channel number of the top convolutional layer. In comparison with our previous work, the significance of discrimination has been improved by ∼70%.

The PANDA Barrel DIRC

The PANDA experiment at the international accelerator Facility for Antiproton and Ion Research in Europe (FAIR), Darmstadt, Germany, will address fundamental questions of hadron physics using p̄p annihilations. Excellent Particle Identification (PID) over a large range of solid angles and particle momenta will be essential to meet the objectives of the rich physics program. Charged PID in the target region will be provided by a Barrel DIRC (Detection of Internally Reflected Cherenkov light) counter. The Barrel DIRC, covering the polar angle range of 22–140 degrees, will provide a π/K separation power of at least 3 standard deviations for charged particle momenta up to 3.5 GeV/c. The design of the Barrel DIRC features narrow radiator bars made from synthetic fused silica, an innovative multi-layer spherical lens focusing system, a prism-shaped synthetic fused silica expansion volume, and an array of lifetime-enhanced Microchannel Plate PMTs (MCP-PMTs) to detect the hit location and arrival time of the Cherenkov photons. Detailed Monte-Carlo simulations were performed, and reconstruction methods were developed to study the performance of the system. All critical aspects of the design and the performance were validated with system prototypes in a mixed hadron beam at the CERN PS. In 2020 the PANDA Barrel DIRC project advanced from the design stage to component fabrication. The series production of the fused silica bars was successfully completed in 2021 and delivery of the MCP-PMTs started in May 2022.

Research on the application of pulse shape discrimination method in (n, lcp) reaction cross-section measurements

The China Spallation Neutron Source Back-n white neutron source supplies neutrons with a wide energy range for nuclear data measurements and nuclear techniques. In cross-section measurements of neutron induced light charged-particle emission (n, lcp) reactions at Back-n, the identification of charged particles are usually achieved with the ΔE-E method or a two-dimensional spectrum of the signal amplitude of the particles deposited in the detector and the corresponding neutron energies derived from the time of flight, called amplitude-En method. Nevertheless, a deficiency still exists in the measurement range and the identification performance with these methods. The pulse shape discrimination (PSD) method with a silicon detector is supposed to be a supplement to the amplitude-En and ΔE-E methods. With silicon detectors, experiments have been performed to compare the performance of the amplitude-En and the PSD methods. The PSD method shows a good performance in identifying light charged particles in the MeV neutron energy region. Alphas and tritons emitted from 6Li(n, t) reaction can be identified with the low energy threshold around 2.5 MeV. This provides an effective method for the cross-section measurement of (n, lcp) reactions at Back-n.

Performance of a prototype TORCH time-of-flight detector

TORCH is a novel time-of-flight detector, designed to provide charged particle identification of pions, kaons and protons in the momentum range 2–20 GeV/c over a 9.5 m flight path. A detector module, comprising a 10 mm thick quartz plate, provides a source of Cherenkov photons which propagate via total internal reflection to one end of the plate. Here, the photons are focused onto an array of custom-designed Micro-Channel Plate Photo-Multiplier Tubes (MCP-PMTs) which measure their positions and arrival times. The target time resolution per photon is 70 ps which, for 30 detected photons per charged particle, results in a 10–15 ps time-of-flight resolution. A 1.25 m length TORCH prototype module employing two MCP-PMTs has been developed, and tested at the CERN PS using a charged hadron beam of 8 GeV/c momentum. The construction of the module, the properties of the MCP-PMTs and the readout electronics are described. Measurements of the collected photon yields and single-photon time resolutions have been performed as a function of particle entry points on the plate and compared to expectations. These studies show that the performance of the TORCH prototype approaches the design goals for the full-scale detector.

Overview of the PANDA detector design at FAIR

PANDA (antiProton ANihilation at DArmstadt) is the central experiment to fully exploit the physics research potential of antiproton beams at the international accelerator Facility for Antiproton and Ion Research in Europe (FAIR), currently under construction at GSI. Phase-space cooled high intensity antiproton beams up to 15 GeV/c will be provided by the High Energy Storage Ring (HESR) at FAIR to interact with PANDA internal proton or nuclear targets enabling a broad range of exciting studies in Particle and Nuclear Physics. The PANDA detector features two spectrometers, the Target Spectrometer with a superconducting solenoid magnet of 2 T around the interaction region with hermetic coverage and the Forward Spectrometer with a 2 Tm dipole magnet for coverage of the forward boosted particles. Several modern particle detector systems are employed in PANDA to provide excellent charged particle tracking, particle identification, calorimetry and muon detection, over the full momentum range in both spectrometers throughout the lifetime of the experiment. Focusing on the various PANDA detector systems we present an overview of recent developments, the detector construction progress and conclude with an outline for a phased deployment of PANDA at FAIR.

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.

Charged particle identification performance of the TOP counters in Belle II

The Time-Of-Propagation (TOP) counter is a novel ring-imaging Cherenkov detector that primarily consists of a quartz bar radiator, micro-channel plate photomultipliers and front-end readout electronics. These TOP counters are installed in the central region of the Belle II detector to provide the crucial information on the charged particle identification (PID). Here, we present an overview of PID studies in Belle II, with a focus on the performance of the TOP detector. The results presented are from the recently recorded data which show reasonable agreement with the expectations from the simulation studies.

New trapezoid-shaped Frisch-grid ionization chamber for low-energy particle measurements

A new trapezoid-shaped Frisch-grid ionization chamber (TFG-IC) has been built as a part of a varDelta {E}-E telescope system for the detection and identification of charged particles at energies down to a few MeV. To study the effect of the drift electric field uniformity, two types of sealed windows, namely a pair of SSA (split-strip aluminized mylar film) and a pair of DSA (double-sided aluminized mylar film) sealed windows have been investigated. The detector’s performances were studied using a standard ^{241}Am source at different gas pressures, and the total energy-deposit resolution achieved is about 1.1%(FWHM). The varDelta {E}-E telescope, which was composed of TFG-IC and a DSSSD (double-sided silicon strip detector), has been tested using a three-component alpha source and the ^{241}Am source under laboratory conditions. The results show that the energy resolution with the SSA sealed windows which provide uniform drift electric field has a smaller fluctuation than that with the DSA ones; the fluctuations are about 1% and 4% for the former and the latter, respectively. Simulations using the COMSOL software also confirmed the electric-field distortion at the edge of the detector with the DSA windows. A correlation curve between energy resolution and energy deposit of charged particles at various gas pressures and for two gas species is derived for TFG-IC with the SSA sealed windows using the measurement with the ^{241}Am source. Incorporating the above results, we performed Monte Carlo simulations to evaluate the particle-identification capability of the telescope. The results show that the telescope can be extended to the identification of low-energy particles.

New developments from the TORCH R&D project

TORCH is a large-area and high-precision time-of-flight detector, designed to provide charged particle identification over a 2–20GeV/c momentum range. The TORCH detector comprises a 10 mm thick quartz radiator, instrumented with photon detectors, which precisely time and measure the arrival positions of the Cherenkov photons. The photon detectors are micro-channel plate photo-multiplier tubes (MCP-PMTs) comprising a finely segmented anode of 64 × 64 anode pads, electronically ganged into 64 × 8 pixels, over a 53 × 53mm2 area, an excellent intrinsic time resolution of ∼ 30ps, and a long lifetime of up to ≳ 5C/cm2. The current version of the MCP-PMTs used by TORCH have been developed with an industrial partner, Photek Ltd, to satisfy the stringent requirements of the detector. The TORCH R&D programme has successfully demonstrated the detector concept through extensive laboratory and beam tests. A TORCH prototype has been constructed and has yielded encouraging results when exposed to low momentum charged hadrons. Characteristic patterns of Cherenkov photons have been recorded, illustrating the required spatial accuracy and timing resolution of 70 ps per photon. Both laboratory and beam test results are approaching the design goals of the TORCH detector.

Picosecond timing of charged particles using the TORCH detector

TORCH is a large-area, high-precision time-of-flight (ToF) detector designed to provide charged-particle identification in the 2–20 GeV/c momentum range. Prompt Cherenkov photons emitted by charged hadrons as they traverse a 10 mm quartz radiator are propagated to the periphery of the detector, where they are focused onto an array of micro-channel plate photomultiplier tubes (MCP-PMTs). The position and arrival times of the photons are used to infer the particles’ time of entry in the radiator, to identify hadrons based on their ToF. The MCP-PMTs were developed with an industrial partner to satisfy the stringent requirements of the TORCH detector. The requirements include a finely segmented anode, excellent time resolution, and a long lifetime. Over an approximately 10 m flight distance, the difference in ToF between a kaon and a pion with 10 GeV/c momentum is 35 ps, leading to a 10–15 ps per track timing resolution requirement. On average 30 photons per hadron are detected, which translates to a single-photon time resolution of 70 ps. The TORCH R&D program aims to demonstrate the validity of the detector concept through laboratory and beam tests, results from which are presented. A timing resolution of 70–100 ps was reached in beam tests, approaching the TORCH design goal. Laboratory timing tests consist of operating the MCP-PMTs coupled to the TORCH readout electronics. A time resolution of 50 ps was measured, meeting the TORCH target timing resolution.

Charged Particle Identification by the Time-of-Flight Method in the BM@N Experiment

Charged Particle Identification by the Time-of-Flight Method in the BM@N Experiment

First observation of quasi–monochromatic optical Cherenkov radiation in a dispersive medium (quartz)

The present article summarizes the results of a study of optical Cherenkov radiation (ChR) spectral properties both theoretically and experimentally. This type of radiation has a continuous spectral distribution which allows to use it in different fields of physics as for charged particle identification or generation of intense THz radiation. By exploiting the frequency dependency of the target permittivity it is possible to observe quasi–monochromatic radiation. A theoretical model based on a surface current approach is presented which allows to predict angular and spectral properties of ChR. In order to test the model predictions, an experiment was carried out using 855 MeV electrons and a 0.2 mm thick quartz target as radiator which could be rotated with respect to the beam axis. Quasi–monochromatic ChR was observed with a spectrometer placed at a fix observation angle, and tilting the radiator crystal offered the possibility to tune the radiation wavelength. The monochromatization effect is attributed to the frequency dependency of the quartz permittivity, and taking into account the refraction law for emitted ChR crossing the boundary between radiator target and vacuum it is possible to deduce a dispersion relation which connects ChR wavelength and outgoing photon angle - or in an alternative way ChR wavelength and target tilt angle for fixed observation angle. The dispersion relation is clearly confirmed in the experiment, and the model predictions show a satisfactory agreement with the measurements. Exploiting the ChR monochromatization mechanism might offer versatile tools which can find applications for example in beam diagnostics at modern particle accelerators.

Charged particle identification with the liquid xenon calorimeter of the CMD-3 detector

The paper describes a method of the charged particle identification, developed for the CMD-3 detector, installed at the VEPP-2000 e+e− collider. The method is based on application of boosted decision trees classifiers, trained for the optimal separation of electrons, muons, pions and kaons in the momentum range from 100 to 1200MeV/c. The input variables for the classifiers are linear combinations of the energy depositions of charged particles in 12 layers of the liquid xenon calorimeter of the CMD-3. The event samples for training of the classifiers are taken from the simulation. Various issues of the calorimeter strip channels response simulation and their calibration are considered. Application of the method is illustrated by the examples of separation of the e+e−(γ) and π+π−(γ) final states and of selection of the K+K− final state at high energies.

Probing QCD with LHCb

While the LHCb detector was specifically designed for measuring heavy-flavor physics, it has also proven itself as a forward general purpose detector with flexible data acquisition, excellent lifetime resolution and charged particle identification. This makes LHCb an ideal laboratory for exploring phenomena related to quantum chromodynamics (QCD), particularly with heavy-flavor content. This review explores some of the novel QCD measurements from LHCb, with an emphasis placed on comparisons to predictions from the Pythia 8 Monte Carlo event generator.

K^{+}Lambda photoproduction at forward angles and low momentum transfer

gamma p rightarrow K^{+} Lambda differential cross sections and recoil polarisation data from threshold for extremely forward angles are presented. The measurements were performed at the BGOOD experiment at ELSA, utilising the high angular and momentum resolution forward spectrometer for charged particle identification. The high statistics and forward angle acceptance enables the extraction of the cross section as the minimum momentum transfer to the recoiling hyperon is approached.

MTOF performance during the first main commissioning beam time at mCBM

The future Facility for Anti-proton and Ion Research (FAIR), currently in construction in Darmstadt, Germany, is one of the largest research projects worldwide. The Compressed Baryonic Matter (CBM) experiment is one of the main pillars at FAIR, studying the quantum chromodynamics (QCD) phase diagram at high baryon densities with unprecedented interaction rate in heavy ion collisions up to 10 MHz. This requires new data-driven readout chain, new data analysis methods and high-rate capable detector systems. The task of the CBM Time-of-Flight wall (CBM-TOF) is the charged particle identification. Multi-gap Resistive Plate Chambers (MRPCs) with different rate capabilities will be used at CBM-TOF corresponding regions. To reduce the commissioning time for CBM, a CBM full system test-setup called mini-CBM (mCBM) had been installed and tested with beams at GSI SIS18 facility in March 2019, which was the first main commissioning beam time at mCBM. These tests were not only system tests to make preparations for CBM but also commissioning runs for mCBM which finally aims at measuring Lambda baryon production with high rate up to 10 MHz. High-rate MRPC prototypes equipped with low resistive glass called MRPC2, were selected to be implemented in mTOF modules for mCBM. The first test results of MRPC2 and the mTOF system will be shown.