Separation Of Showers Research Articles

Shower separation in five dimensions for highly granular calorimeters using machine learning

To achieve state-of-the-art jet energy resolution for Particle Flow, sophisticated energy clustering algorithms must be developed that can fully exploit available information to separate energy deposits from charged and neutral particles. Three published neural network-based shower separation models were applied to simulation and experimental data to measure the performance of the highly granular CALICE Analogue Hadronic Calorimeter (AHCAL) technological prototype in distinguishing the energy deposited by a single charged and single neutral hadron for Particle Flow. The performance of models trained using only standard spatial, energy and charged track position information from an event was compared to models trained using timing information available from AHCAL, which is expected to improve sensitivity to shower development and, therefore, aid in clustering. Both simulation and experimental data were used to train and test the models and their performances were compared. The best-performing neural network achieved significantly superior event reconstruction when timing information was utilised in training for the case where the charged hadron had more energy than the neutral one, motivating temporally sensitive calorimeters. All models under test were observed to tend to allocate energy deposited by the more energetic of the two showers to the less energetic one. Similar shower reconstruction performance was observed for a model trained on simulation and applied to data and a model trained and applied to data.

Design and optimization of the CEPC scintillator hadronic calorimeter

The Circular Electron Positron Collider (CEPC) is a next-generation electron–positron collider proposed for precision measurement of the properties of the Higgs boson. A major challenge for the CEPC detector is achieving a boson mass resolution (BMR) of 4%, which is required to separate the Higgs, Z, and W bosons in their hadronic decays. The baseline design of the CEPC detector was guided by the particle flow algorithm (PFA) concept to satisfy the BMR requirements. The BMR performance obtained by the PFA approach is primarily determined by the shower separation capability and energy resolution of the calorimeters of the detector system. A hadronic calorimeter with high granularity is crucial for providing the required separation power and energy resolution for the desired BMR. In this context, the analogue hadron calorimeter (AHCAL), a scintillator hadronic calorimeter with analogue readout, is a potential hadronic calorimeter option for the CEPC detector. In this study, key design parameters of the AHCAL, including scintillator cell size, number of sampling layers, absorber thickness, and scintillator thickness, were optimized for BMR performance on the benchmark process of e + e - ⟶ νν̅H,H ⟶ gg. Notably, herein, a set of optimized design parameters is presented for the CEPC AHCAL that meets the required BMR with reduced readout channels. Specifically, the set of proposed AHCAL design parameters is as follows: 40 sampling layers, 20 mm steel thickness, and 40× 40× 3 mm3 scintillator size for every tile. This design achieves a BMR of 3.73% and remarkably reduces the number of readout channels.

The SiD Digital ECal Based on Monolithic Active Pixel Sensors

The SiD detector concept capitalizes on high granularity in its tracker and calorimeter to achieve the momentum resolution and particle flow calorimetry physics goals in a compact design. The collaboration has had a long interest in the potential for improved granularity in both the tracker and ECal with an application of monolithic active pixel sensors (MAPS) and a study of MAPS in the SiD ECal was described in the ILC TDR. Work is progressing on the MAPS application in an upgraded SiD design with a prototyping design effort for a common SiD tracker/ECal design based on stitched reticules to achieve 10 × 10 cm2 sensors with 25 × 100 micron2 pixels. Application of large area MAPS in these systems would limit delicate and expensive bump-bonding, provide possibilities for better timing, and should be significantly cheaper than the TDR concept due to being a more conventional CMOS foundry process. The small pixels significantly improve shower separation. Recent simulation studies confirm previous performance projections, indicating electromagnetic energy resolution based on digital hit cluster counting provides better performance than the SiD TDR analog design based on 13 mm2 pixels. Furthermore, the two shower separation is excellent down to the millimeter scale. Geant4 simulation results demonstrate these expectations.

Wire-cell 3D pattern recognition techniques for neutrino event reconstruction in large LArTPCs: algorithm description and quantitative evaluation with MicroBooNE simulation

Wire-Cell is a 3D event reconstruction package for liquid argon time projection chambers. Through geometry, time, and drifted charge from multiple readout wire planes, 3D space points with associated charge are reconstructed prior to the pattern recognition stage. Pattern recognition techniques, including track trajectory and dQ/dx (ionization charge per unit length) fitting, 3D neutrino vertex fitting, track and shower separation, particle-level clustering, and particle identification are then applied on these 3D space points as well as the original 2D projection measurements. A deep neural network is developed to enhance the reconstruction of the neutrino interaction vertex. Compared to traditional algorithms, the deep neural network boosts the vertex efficiency by a relative 30% for charged-current νe interactions. This pattern recognition achieves 80–90% reconstruction efficiencies for primary leptons, after a 65.8% (72.9%) vertex efficiency for charged-current νe (νμ) interactions. Based on the resulting reconstructed particles and their kinematics, we also achieve 15-20% energy reconstruction resolutions for charged-current neutrino interactions.

CALICE scintillator HCAL - Electromagnetic and hadronic shower analysis

The CALICE test beam calorimeters operated at the CERN SPS facility have collected a large sample of hadronic and electromagnetic showers with unprecedented granularity.The calorimeters and beam line instrumentation are modeled in the MOKKA framework and full simulation of the test beam experiment is performed using GEANT4. Digitization is applied to each calorimeter to account for detector effects and noise. The scintillator-based hadronic calorimeter (AHCAL) is the center of the studies reported in this paper. The most important validation of the detector modeling and calibration chain is the test of the calorimeter response linearity and resolution for a large range on incident beam energies. Electromagnetic showers are the most demanding test since the energy deposited per single tile in an electromagnetic shower is larger than in a hadronic shower for the same beam energy. Results of the calorimeter response to muons and positrons are discussed and compared to Monte Carlo (MC).The analysis of single pion showers, recorded with the AHCAL offer the unique possibility to test hadronic shower models using a number of different observables. Total energy and longitudinal profiles have been studied at first and compared with two available shower models in GEANT4. Results of the effect of the shower leakage on the reconstructed energy and energy resolution are presented. Furthermore, studies of shower separation are performed using event mixing techniques. Shower separation is critical for the performance of modern particle flow algorithms, which here for the first time can be tested on experimental data.

On the application of differences in intrinsic fluctuations of Cherenkov light images for separation of showers

The sensitivity of ground-based imaging atmospheric Cherenkov γ-ray observatories depends critically on the primary particle identification methods which are used to retain photon-initiated events and suppress the spurious background produced by cosmic rays. We suggest a new discrimination technique which utilizes differences in the fluctuations of the light intensity in the images of showers initiated by photons and those initiated by protons or heavier nuclei. The database of simulated events for the proposed VERITAS observatory has been used to evaluate the efficiency of the new technique. Analysis has been performed for both a single VERITAS imaging telescope, and a system of these telescopes. We demonstrate that a discrimination efficiency of ⩾1.5–2.0 can be achieved in addition to traditional background rejection methods based on image shape parameters.

About a possibility of the analysis of the mass composition of cosmic rays on the basis of the space-temporal distribution of the EAS Cherenkov light

The space-temporal distribution of the EAS Cherenkov light initiated by p, α and nuclei of M H VH groups in energy region 1 ÷ 20 TeV per nucleus is investigated using the Monte-Carlo method. Essential differences are found in the shape of the front and fluctuations of the Cherenkov light from air showers created by different primary nuclei. These differences can be successfully applied for the separation of showers. Particularly, for selection criteria directed at the separation of showers of M group we have the suppression factor of protons ~ 50. For VH group a practically complete suppression of protons is possible.

Study of mass composition and energy spectrum of primary cosmic radiation by the imaging atmospheric Cherenkov technique

Imaging atmospheric Cherenkov telescopes (IACT) have proven to be, up to now, the most effective instruments for the observation of primary TeV -radiation from astrophysical objects. The high detection rate as well as the capability of accurate reconstruction of air-shower parameters by the IACT technique also allow the use of the imaging technique for the study of the energy spectrum and mass composition of cosmic rays. In this paper we discuss the potential of this technique for the separation of different components of cosmic rays in the energy region 1-. We show that the imaging technique allows adequate separation of showers produced by protons from the contributions of all other nuclei, including -particles, and thus allows a measurement of the energy spectrum of the proton component at TeV energies. Such measurements can currently be performed by operating single IACTs designed originally for -ray astronomical purposes. The effective separation of different nucleus groups of the cosmic radiation is a more difficult problem. It benefits from the stereoscopic reconstruction of the shower development in the Earth's atmosphere. Our calculations show that simultaneous detection of air showers by two IACTs located at a distance of about 100 m from each other allows an effective separation of the proton, -particle, medium (O), heavy (Si), and very heavy (Fe) groups of cosmic-ray nuclei.

A high resolution BGO calorimeter with longitudinal segmentation

We report on the construction and test results of a 8 × 8 module electromagnetic BGO calorimeter with both longitudinally non-segmented modules and modules with longitudinal segmentation for improved electron/hadron discrimination and two shower separation. The data have been taken mainly at the CERN PS accelerator at electron and pion momenta ranging from 0.5–6 GeV/ c. The crystals are read out via large area silicon PIN photodiodes coupled to specially developed low-noise preamplifiers and pulse-processor modules with automatic gain range selection. We discuss the energy and position resolution as well as the performance for particle identification and two shower separation.

Hadrons in EAS initiated by cosmic gamma-rays with ultra-high energy

EAS initiated by primary gamma -quanta with constant size at mountain altitude are simulated using three-dimensional Monte Carlo procedures based on a realistic phenomenological interaction model SM1. The definitive role of the reception conditions of the applied EAS arrays for the selection of showers initiated by primary gamma -quanta with ultra-high energies is shown. The criterion (Eh/Ee)r<or=3m<or=1.4*10-2 to select hadron-poor EAS as gamma -showers is confirmed for the Tien Shan experiment. It is shown that only the method of hadronless EAS selection offers a real possibility for a full separation of showers initiated by primary gamma -quanta, from the background events.

An electron-hadron separator for digital sampling calorimeters

A fast and effective algorithm for electromagnetic and hadronic shower separation has been developed for the digital sampling calorimeter of the CHARM II experiment. It is based on a generalization of the minimal spanning tree concept and can be easily applied to other existing calorimeters. In this particular application, which requires the highest efficiency for retaining electromagnetic showers, one gets, for 99% efficiency, a rejection factor of the order of 100 for hadronic showers.

Characteristics of hadronic showers detected by Cherenkov radiation in lead glass

Spatial and energy characteristics of hadron showers were studied for the first time with the help of a total hadron absorption detector made from lead glass. The calorimeter model having a longitudinal and transverse hodoscopic structure with 10 cm step width is exposed to a particle beam of e +, μ +, π +, K +, p at 5, 10 and 13 GeV/ c. Data on the energy and coordinate resolution, hadron and electromagnetic shower separation have been obtained.

Use of a cathode read-out multiwire proportional chamber for separation of electronagnetic and hadronic showers

Data are presented for separation of showers produced by 1–4 GeV/ c incident electrons and pions after the traversal of ∼ 1 radiation length of aluminium. The use of a cathode strip read-out multiwire proportional chamber and a scintillation counter is shown to improve the rejection obtained with lead-glass counters, giving as much as a factor of 80 at 50% detection efficiency. The parameters of the chamber are: cathode plane to plane gap 1.2 cm, wire spacing 0.2 cm, width of the cathode strips 1 cm, interstrip 0.2 cm, sensitive area of the chamber 20×20 cm 2.