Hadron Rejection Research Articles

Prediction of using LHAASO’s cosmic-ray electron measurements to constrain decaying heavy dark matter

Large High Altitude Air Shower Observatory (LHAASO) is an instrument designed for detecting cosmic rays (CRs) and gamma rays at TeV to PeV energies. The decays of heavy dark matter particles in the Galactic halo may produce high-energy electrons that can be detected by LHAASO. The main background for the LHAASO's CR electron measurements is the hadron residuals due to misidentification of the particle species. In this paper, we estimate the LHAASO's electron background using the known all-particle CR spectrum and the hadron rejection efficiency of LHAASO. With the estimated background, we predict the capability of LHAASO to constrain dark matter (DM) decay lifetime at 95% confidence level for various channels. We find that if neglecting systematic uncertainties, the CR electron measurement by LHAASO can improve the current best results by up to one order of magnitude for DM masses between 100--1000 TeV. However, indirect measurements of CR electrons by ground-based experiments suffer from sizable systematic uncertainties. With the systematic uncertainties included in the calculation, the projected constraints will be largely weakened. So, for using the CR electron observation of LHAASO to constrain the DM parameters, the key point is whether the systematic error can be effectively reduced.

Construction and test of a transition-radiation detector prototype based on thick gas electron multiplier technology

A transition-radiation detector (TRD) is a powerful device for highly relativistic electron (γ ≳ 1,000) identification. Electron identification is crucial for tagging the outgoing scattered electrons in an electron-ion collider (EIC) detector. Employing a TRD at the electron forward region of an EIC detector can provide the necessary electron identification with high hadron rejection over a wide momentum range. Thick gas electron multiplier (THGEM) technology is suitable for radiation detection in modern high-energy experiments owing to its high-granularity structure, radiation hardness, high-rate capability and ease of large-area production. This study investigates a TRD prototype based on THGEM technology through soft X-ray and electron beam experiments. Geant4 simulation were extensively exploited to understand the operation of TRD prototype with different gas mixtures. Particularly, the performance of TRD prototype with an electron beam at the DESY, with argon-based gas rather than xenon-based gas, agreed well with the simulation analyses in all important aspects. Based on the consistency of the experimental and simulation results, a likelihood analysis on the simulated total energy deposit in the xenon-based working gas would suggest a pion rejection improvement with the optimization of detector design, readout electronics and identification algorithm.

Properties of a Simple е/γ Detector Consisting of a Lead Convertor and a Hodoscope

The results of the calculations of coordinate resolution and hadron rejection factor for a simple e/gamma detector consisting of a lead convertor followed by a hodoscope are presented. For the simulation of showers, initiated in the converter by electrons and hadrons with energies upto 1 TeV GEANT4 is used. It is shown that the best coordinate resolution for electrons is achieved when the converter thickness is closed to the shower maximum. For example, at 200 GeV with 2 mm strip width hodoscope it is equal to sigma=89 microns provided a "truncated mean" coordinate estimation is used. The optimal thickness of the converter for hadron rejection is also close to tmax. For 200 GeV beam of electrons and protons the rejection factor of 10^-4 for 0.9 electron detection efficiency can be reached using only data on charged particles multiplicities. Information on the spatial distribution of the shower particles after the converter allows to enhance further the rejection by several times.

Optimization of the Neutron Detector Design Based on the 6LiF/ZnS(Ag) Scintillation Screens for the GAMMA-400 Space Observatory

The Neutron Detector (ND) is a new detector sub-system for the future GAMMA-400 space observatory. It aims to complement the instrument's GAMMA-400 electromagnetic calorimeter (CsI(Tl), total depth is 25.0 X0) in identifying cosmic-ray electrons from ∼ 100 MeV up to 3 TeV. Such electrons are of significant scientific interest, but their identification is complicated by the overwhelmingly more abundant hadronic cosmic rays, hence making significant hadronic rejection power of paramount importance. Particle showers initiated by nuclei in the GAMMA-400 calorimeter have a profile different from an electron-induced electromagnetic cascade, and the hadron rejection power deriving from this difference can be significantly enhanced by making use of the thermal neutron activity at late (>100ns) times relative to the start of the shower. Indeed hadron-induced showers tend to be accompanied by significantly more neutron activity than electromagnetic showers. In the described ND for capturing thermalized neutrons applied isotope 6Li, which is part of the scintillation screen 6LiF/ZnS(Ag). ND placed are under the electromagnetic calorimeter. The results GEANT4 simulation of the ND shows that ND has high neutron detection efficiency.

Performance of prototypes for the ALICE electromagnetic calorimeter

The performance of prototypes for the ALICE electromagnetic sampling calorimeter has been studied in test beam measurements at FNAL and CERN. A 4 × 4 array of final design modules showed an energy resolution of about 11 % / E ( GeV ) ⊕ 1.7 % with a uniformity of the response to electrons of 1% and a good linearity in the energy range from 10 to 100 GeV. The electromagnetic shower position resolution was found to be described by 1.5 mm ⊕ 5.3 mm / E ( GeV ) . For an electron identification efficiency of 90% a hadron rejection factor of > 600 was obtained.

The CALET mission for detection of cosmic ray sources and dark matter

We are developing the CALorimetric Electron Telescope, CALET, mission for the Japanese Experiment Module Exposed Facility, JEM-EF, of the International Space Station. Major scientific objectives are to search for nearby cosmic ray sources and dark matter by carrying out a precise measurement of the electrons in 1 GeV - 10 TeV and the γ rays in 20 MeV - several TeV. CALET has a unique capability to observe electrons and γ rays over 1 TeV since the hadron rejection power is more than 105 and the energy resolution better than a few % over 100 GeV. The detector consists of an imaging calorimeter by SciFi and W, and a total absorption calorimeter by BGO. CALET has also a capability to measure protons and nuclei up to 1000 TeV, and will have a function to monitor solar activity and γ ray bursts with additional instruments. The phase A study has started on a schedule of launch in 2013 by H-II Transfer Vehicle (HTV) for 5 years observation.

The CALET experiment on ISS

We are preparing the CALorimetric Electron Telescope, CALET, mission for the Japanese Experiment Module Exposed Facility, JEM-EF, of the International Space Station. The scientific objective is to reveal unresolved problems in high-energy phenomena of the Universe by carrying out a precise measurement of the electrons in 1 GeV ∼ 10 TeV and the γ − rays in 20 MeV ∼ several TeV. The CALET has a unique capability to measure the electrons and γ -rays over 1 TeV since the hadron rejection power might be as much as ∼ 10 6 and the energy resolution of electromagnetic particles better than a few % over 100 GeV. Therefore, it is promising to detect the change of energy spectra related to the acceleration, source and propagation of cosmic-rays and the γ -ray line signature expected from dark matter annihilation. We will discuss not only the science but the techniques, the observation and the current status of project. The CALET is expected to be launched around 2012 by the Japanese H-II Transfer Vehicle, HTV, and to be on orbit for three years.

CALET for High Energy Electron and Gamma-Ray Measurements on ISS

The CALorimetric Electron Telescope, CALET, mission is proposed for the Japanese Experiment Module Exposed Facility, JEM-EF, of the International Space Station. The mission goal is to reveal the high-energy phenomena in the universe by carrying out a precise mesurement of the electrons in the range 1 GeV-10 TeV and the gamma-rays in the range 20 MeVto several TeV. The detector will be composed of an imaging calorimeter of scintillating fibers (IMC) and a total absorption calorimeter of BGO (TASC). The total absorber thickness is 36 r.l for electromagnetic particles and 1.8 m.f.p for protons. The total pay-load weight is nearly 2.5 t and the effective geometrical factor for the electrons ∼1.0 m 2 sr. The CALET has a unique capability to measure the electrons and gamma-rays above 1 TeV since the hadron rejection power can be 10 6 and the energy resolution for electromagnetic particles is better than a few % above 100 GeV. Therefore, it is promising to detect any change of the energy spectra and a line signature in the energy distribution, as expected from the dark matter.

The CALET, CALorimetric Electron Telescope, on ISS/JEM

The CALorimetric Electron Telescope, CALET, mission is proposed for the Japanese Experiment Module Exposed Facility, JEM-EF, of the International Space Station. The mission goal is to reveal the high-energy phenomena in the universe by carrying out a precise mesurement of the electrons in 1 GeV – 10 TeV and the gamma-rays in 20 MeV – several TeV. The instrument will be composed of an imaging calorimeter of scintillating fibers and a total absorption calorimeter of BGO. The total thickness of absorber is 36 r.l for electro-magnetic particles and 1.8 m.f.p for protons. Total weight of the payload is nearly 2,500 kg, and the effective geometrical factor for the electrons might be ∼ 1.0 m2sr. The CALET has a unique capability to measure the electrons and gamma-rays over 1 TeV since the hadron rejection power can be 106 and the energy resolution of electro-magnetic particles is better than a few % over 100 GeV. Therefore, it is promissing to detect the change of energy spectra and the line feature of energy distribution expected from the dark matter. We are expecting to launch the CALET around 2010 by the Japanese H-II Transfer Vehicle, HTV, and to carry out the observation more than three years.

High-pT electron distributions in d+Au and p+p collisions at RHIC

We present preliminary measurements of electron and positron spectra in d+Au and p+p collisions at for 1.5 < pT < 7.0 GeV/c. These measurements were carried out using the STAR time projection chamber (TPC) and the barrel electromagnetic calorimeter (EMC). Overall hadron rejection factors in the range of 105 have been achieved. In this work, we describe the measurement technique used to discriminate electrons from hadrons and compare the results for single electron spectra with Pythia-based pQCD calculations for electrons from heavy-quark semi-leptonic decays.

The CALET, CALorimetric Electron Telescope, mission for the International Space Station

The CALorimetric Electron Telescope, CALET, mission is proposed for the Japanese Experiment Module Exposure Facility of the International Space Station. Major goals of the mission are precise measurements of the electrons in a few GeV - 10 TeV and the gamma-rays in 100 MeV - several TeV, keeping an energy resolution of a few % over 100 GeV. From the measurements, a systematic investigation of high-energy electromagnetic process in universe will be performed. A detection of SUSY particle which is a candidate of the dark matter would also be expected. The detector is composed of an imaging calorimeter of scintillating fibers and a total absorption calorimeter. Total thickness of the absorber is 45 r.1 for electro-magnetic particles and 2.1 m.f.p for protons. Total weight of the payload is nearly 2,200 kg, and the effective geometrical factor should be ∼ 1.0 m 2sr. The hadron rejection power can be 10 6 for electrons.

Performance of the electromagnetic calorimeter of the HERMES experiment

The performance of the electromagnetic calorimeter of the HERMES experiment is described. The calorimeter consists of 840 radiation resistant F101 lead-glass counters. The response to positrons up to 27.5 GeV, the comparison between the measured energy and the momentum reconstructed from tracking, long-term stability, hadron rejection and neutral meson invariant mass reconstruction are shown.

A new analysis method for very high definition Imaging Atmospheric Cherenkov Telescopes as applied to the CAT telescope

A new method of shower-image analysis is presented which appears very powerful as applied to those Cherenkov Imaging Telescopes with very high definition imaging capability. It provides hadron rejection on the basis of a single cut on the image shape, and simultaneously determines the energy of the electromagnetic shower and the position of the shower axis with respect to the detector. The source location is also reconstructed for each individual γ-ray shower, even with one single telescope, so for a point source the hadron rejection can be further improved. As an example, this new method is applied to data from the CAT (Cherenkov Array at Thémis) imaging telescope, which has been operational since Autumn, 1996.

Particle identification performance of a straw transition radiation tracker prototype

An 864 channel prototype of an integrated straw tracker and transition radiation detector for tracking and electron identification has been tested with and without magnetic field at the CERN SPS. The rejection against hadrons and converted photons has been measured and the dependence of the rejection power on detection parameters has been investigated. Tracking and hadron rejection were also studied in a high multiplicity environment. The results are compared with Monte Carlo simulations. Wherever possible, conclusions are drawn concerning the performance of a full-scale detector at the future Large Hadron Collider.

Low threshold particle arrays

While atmospheric Cherenkov telescopes have a small field of view and a small duty fraction, arrays of particle detectors on ground have a 1 sr field of view and a 100% duty fraction. On the other hand, particle detector arrays have a much higher energy threshold and an inferior hadron rejection as compared to Cherenkov telescopes. Low threshold particle detector arrays would have potential advantages over Cherenkov telescopes in the search for episodic or unexpected sources of gamma rays in the multi-TeV energy range. Ways to improve the threshold and hadron rejection of arrays are shown, based on existing technology for the timing method (with scintillator or water Cherenkov counters) and the tracking method (with tracking detectors). The performance that could be achieved is shown by examples for both methods. At mountain altitude (about 4000 m or above) an energy threshold close to 1 TeV could be achieved. For any significant reduction of the hadronic background by selecting muon-poor showers a muon detection area of at least 1000 m2 is required, even for a compact array.

A new air Cherenkov counter concept for the observation of extended air showers

We are presently building an array of angle integrating air Cherenkov counters for the study of VHE and UHE cosmic rays. The new array will be sensitive to extended air showers of energies > 5 × 10 13 meV and of zenith angles up to 35°. The determination of the incident shower direction will be performed by fast timing measurements with an angular resolution of 0.5–5 mrad. The Cherenkov counters will allow us to obtain information on the shower energy and structure higher up in the atmosphere. The array will be combined with the existing HEGRA scintillation counter matrix on La Palma. The combination of the Cherenkov data and the data from the ground level scintillator matrix will provide a powerful tool for γ/hadron discrimination. We expect to achieve hadron rejection ratios of > 10 3 when adding the proposed muon detectors, thereby making possible the detection of the diffuse γ radiation presumed to be coming predominantly from the galactic plane.

A hadron-blind detector

The development of highly efficient solid photocathodes, compatible with high-gain gaseous detectors, has opened the possibility to build threshold Cherenkov counters with a good hadron rejection, with a minimum amount of matter, and a time resolution of the order of the nanosecond. We discuss the properties of a hadron-blind detector, with a granularity of a few millimetres. The study of the background sources shows that a rejection power of the order of 99% can be achieved for high-energy hadrons. It permits instantaneous multi-hadron rejection and, combined to a fast electromagnetic calorimeter, can ensure on-line electron selection, even when they are produced close to hadronic jets. It could permit the operation of lepton-tracking detectors in a magnetic field, in very high hadronic backgrounds.

A promising large area VHE gamma ray detector with excellent hadron rejection capability

A new large area VHE gamma ray detector for detecting atmospheric Cerenkov light from very high energy celestial gamma rays is proposed. It will be constructed by converting Solar One, a 10 MW Solar Thermal Central Receiver Pilot Plant at Barstow, California, which uses the solar tower technology with heliostats as light collectors. Solar energy research at this facility has recently been terminated. The detector will cover an area of at least 200 m diameter, which is only about 5% of the total area available at Solar One, so that a significant fraction of the Cerenkov light pool is detected. Each heliostat will focus the Cerenkov light onto a photomultiplier tube (PMT) selected to match the optical quality of the heliostat. Its active reflecting surface is 71,000 m 2, which is about 375 times larger than the largest VHE gamma ray atmospheric Cerenkov detector, the twin 11 m dia. collectors at Sandia Labs, Albuquerque 1. It is expected to have the lowest energy threshold (≥10 GeV) for atmospheric Cerenkov observations. This will enhance counting rates significantly and bridge the gap between HE and VHE gamma ray astronomy with some overlapping. It will also have excellent inherent hadron rejection. One hundred million dollars worth of installation is already constructed and ready to use. The rest of the detector can be built for a small fraction, <1%.

Electron-pion separation in a highly segmented electromagnetic calorimeter designed for the ALEPH experiment

In this paper, we will emphasize the advantage we can take of highly segmented electromagnetic calorimeters in both transverse and longitudinal directions. Such calorimeters lead particularly to powerful methods of hadron rejection and electron identification.

The argus electron-photon calorimeter III. Electron-hadron separation

The high granularity of the ARGUS shower counter system allows one to determine the lateral energy deposition. An algorithm based on the number of shower counters set by an incoming particle, the amount of energy deposited in the shower counters and the lateral distribution of the energy allows to separate electrons from muons and hadrons. For electrons with momenta larger than 0.7 GeV/ c the hadron rejection rate is of the order of 50 at an electron detection efficiency of 80%.