Lead-glass Calorimeter Research Articles

Commissioning of a hadron blind detector for dielectron measurement in pA reactions at J-PARC

The J-PARC E16 experiment measures mass spectra of low-mass vector mesons, ρ, ω, and ϕ, in nuclei via e + e - decays. Vector mesons are produced in pA reactions. A spectrometer with a large acceptance and a high-intensity beam up to 1 × 1010 protons per ∼2-sec duration pulse are utilized to collect a sufficient number of vector mesons. We have developed a spectrometer, which has two types of electron identification detectors: a hadron blind detector (HBD) and a lead-glass calorimeter. Commissioning runs have been performed at the J-PARC high-momentum beam line. The HBD successfully observed on average 11 ± 1 photoelectrons for an incident electron. We achieved the pion rejection of 0.9 ± 0.2% with the electron detection efficiency of 61 ± 4% for the HBD, which was consistent of the expected performance.

Optimising longitudinal and lateral calorimeter granularity for software compensation in hadronic showers using deep neural networks

We investigate the effect of longitudinal and transverse calorimeter segmentation on event-by-event software compensation for hadronic showers. To factorize out sampling and detector effects, events are simulated in which a single charged pion is shot at a homogenous lead glass calorimeter, split into longitudinal and transverse segments of varying size, and the total energy loss within each segment is used as the signal. As an approximation of an optimal reconstruction, a neural network-based energy regression is trained based on these signals. The architecture is based on blocks of convolutional kernels customized for shower energy regression using local energy densities; biases at the edges of the training dataset are mitigated using a histogram technique. With this approximation, we find that a longitudinal and transverse segment size less than or equal to 0.5 and 1.3 nuclear interaction lengths, respectively, is necessary to achieve an optimal energy measurement. In addition, an intrinsic energy resolution of 8%/sqrt{E} for pion showers is observed.

The NA62 rare Kaon decay experiment Photon Veto System

The NA62 experiment at CERN SPS is aimed at measuring the rare decay K + → π + ν ν ¯ . This poses very stringent requirements on the particle identification capabilities of the apparatus in order to reject the overwhelming K + → μ + ν and K + → π + π 0 background. In particular, a π 0 rejection at level of 10 − 8 is needed to complement the kinematical rejection of π + π 0 events. In order to have a full acceptance from 0 to 50 mrad, partly covered by NA48 liquid Kripton calorimeter, a set of veto anti-counters should be placed along the vacuum decay tank, to catch large angle photons with a detection efficiency better than 10 − 4 in a wide energy range: from few hundreds MeV to 35 GeV. Intense R&D programs have been carried out in order to study different technological solutions: a lead-scintillating fibers calorimeter, lead-scintillator sandwich calorimeter and finally an original re-use of the existing barrel of the OPAL lead-glass electromagnetic calorimeter. We present the results on detector performances and compare the three solutions.

Calorimetry and Cherenkov radiation

Cherenkov radiation has been frequently used to measure the energy of electromagnetic showers, for instance in lead-glass calorimeters, and now it becomes increasingly useful for hadronic calorimetry as well. A sizable fraction of cascades initiated by hadrons in an absorber is quickly transformed into γ rays, giving e ± as final products. In a transparent active medium, these charged particles can radiate Cherenkov light which, detected with appropriate photosensitive devices, provides a measure of the energy of high energy showering particles. The state of the art in Cherenkov calorimetry and prospects for new types of calorimeters with high granularity and energy resolution are reviewed.

The FLINT setup for studying cumulative processes with photon production

A setup is developed at the Institute for Theoretical and Experimental Physics for studying cumulative processes in hA and AA interactions with photon and π0-meson production in the central region of rapidities at high transverse momenta. Lead glass calorimeters and a charged particle rejection system are the main components of the setup. A fast trigger for a high-energy cumulative particle, based on detection of Cherenkov radiation in the lead glasses, is realized in the setup.

An electromagnetic shower profile in the lead-glass calorimeter in the energy range of 3–23 GeV

The transverse profile of electromagnetic showers in a calorimeter made of TΦ 1-00 lead glass was measured at electron energies of 3, 9, and 23 GeV for two configurations of the setup: with and without an assembly of passive material being placed in front of the calorimeter. The method for obtaining the shower profile did not require the use of high-precision coordinate detectors. Parameterization of shower profiles by a two-dimensional function with two parameters was proposed. A program for simulating Cherenkov light in a lead glass calorimeter was developed. The experimental data agree with the results of Monte Carlo simulation within the limits of experimental errors.

Performance of the radphi detector and trigger in a high rate tagged photon beam

We describe the design and operation of a detector system for measuring all-photon decays of mesons photoproduced in a tagged photon beam with energies between 4.3 and 5.4 GeV and a flux of 5 × 10 7 tagged photons per second. Photons from meson decays were detected with a lead-glass calorimeter with an energy resolution of 11% at 1 GeV. Various veto and trigger components were also present. Final states with as many as six photons were successfully detected and reconstructed.

A bootstrap method for gain calibration and resolution determination of a lead-glass calorimeter

We describe a method for calibration of a lead-glass calorimeter that does not require a beam of known energy. The technique was used to calibrate the radphi lead-glass calorimeter at Jefferson Lab. The technique described can be applied to any segmented electromagnetic calorimeter capable of detecting all-photon decays of mesons, for example, π 0 → 2 γ , η → 2 γ or ω → π 0 γ . We also demonstrate how the measured 2 γ mass width of the π 0 and η mesons can be unfolded to extract the single-shower energy and position resolution functions of the calorimeter.

Polarization Transfer in Proton Compton Scattering at High Momentum Transfer

The Jefferson Lab Hall A experiment E99-114 comprised a series of measurements to explore proton Compton scattering at high momentum transfer. For the first time, the polarisation transfer observables in the p (~ 0 ~ p) reaction were measured in the GeV energy range, where it is believed that quark-gluon degrees of freedom begin to dominate. The experiment utilised a circularly polarised photon beam incident on a liquid hydrogen target, with the scattered photon and recoil proton detected in a lead-glass calorimeter and a magnetic spectrometer, respectively.

The lead-glass electromagnetic calorimeter for the SELEX experiment

A large-acceptance, highly segmented electromagnetic lead-glass calorimeter for Experiment E781 (SELEX) at Fermi National Acceleration Laboratory was designed and built. This detector has been used to reconstruct photons and electrons with energies ranging from a few GeV up to 500 GeV in the collisions of the 600 GeV Σ - hyperons, π mesons and protons with the target nucleons. The design, calibration and performance of the calorimeter are described. Energy resolution and position resolution are assessed using both calibration electron beams and π 0 mesons reconstructed in 600 GeV hadron–hadron interactions. The performance of the calorimeter in selecting resonant states that involve photons is demonstrated.

Lead-Glass Detector for NA49

An experimental report on the construction and operation of a lead-glass calorimeter at the CERN-NA49 experiment is presented.

Basic instrumentation for Hall A at Jefferson Lab

The instrumentation in Hall A at the Thomas Jefferson National Accelerator Facility was designed to study electro- and photo-induced reactions at very high luminosity and good momentum and angular resolution for at least one of the reaction products. The central components of Hall A are two identical high resolution spectrometers, which allow the vertical drift chambers in the focal plane to provide a momentum resolution of better than 2×10 −4. A variety of Cherenkov counters, scintillators and lead-glass calorimeters provide excellent particle identification. The facility has been operated successfully at a luminosity well in excess of 10 38 cm −2 s −1 . The research program is aimed at a variety of subjects, including nucleon structure functions, nucleon form factors and properties of the nuclear medium.

The BLAST project at MIT-Bates

The Bates Large Acceptance Spectrometer Toroid (BLAST) is a detector designed to study the spin-dependent electromagnetic response of few-body nuclei at momentum transfers up to 1 (GeV/c)2 at the MIT/Bates Linear Accelerator Center's South Hall Ring (SHR). The BLAST detector consists of an eight-sector copper coil array producing a toroidal magnetic field, instrumented with two opposing wedge-shaped sectors of wire chambers, scintillation detectors, Cerenkov counters, neutron detectors, a lead-glass forward calorimeter, and recoil detectors. A status of the project is presented as well as highlights of the scientific program.

Status of the BLAST project

The Bates Large Acceptance Spectrometer Toroid (BLAST) is a detector designed to study the spin-dependent electromagnetic response of few-body nuclei at momentum transfers up to 1 (GeV/c)2 at the MIT/Bates Linear Accelerator Center's South Hall Ring (SHR). The BLAST detector consists of an eight-sector copper coil array producing a toroidal magnetic field, instrumented with two opposing wedge-shaped sectors of wire chambers, scintillation detectors, Cerenkov counters, neutron detectors, a lead-glass fo ward calorimeter, and recoil detectors. Presently, BLAST is under construction and it is on schedule to be done in summer 2001. A status of the project is presented as well as highlights of the scientific program.

Equipment selection, automation, and engineering for plating systems

The instrumentation in Hall A at the Thomas Jefferson National Accelerator Facility was designed to study electro- and photo-induced reactions at very high luminosity and good momentum and angular resolution for at least one of the reaction products. The central components of Hall A are two identical high resolution spectrometers, which allow the vertical drift chambers in the focal plane to provide a momentum resolution of better than 2×10−4. A variety of Cherenkov counters, scintillators and lead-glass calorimeters provide excellent particle identification. The facility has been operated successfully at a luminosity well in excess of 1038cm−2s−1. The research program is aimed at a variety of subjects, including nucleon structure functions, nucleon form factors and properties of the nuclear medium.

Dose measurements of bremsstrahlung-produced neutrons from thick targets

Photons of sufficiently high energies ( E γ ≥5–15 MeV) can produce neutrons by means of photonuclear interactions. Bremsstrahlung from high energy electron storage rings, which have an energy range of zero to the maximum energy of the particle beam, can interact with beamline components like beam stops and collimators generating photoneutrons of varying energies. This paper presents the results of simultaneous measurements of bremsstrahlung power and corresponding photoneutron dose equivalent rate at the insertion device beamlines of the Advanced Photon Source, using a lead-glass calorimeter and an Andersson–Braun remmeter. Targets made of Fe, Cu, W, and Pb are placed in the bremsstrahlung beam inside the first optics enclosure of the insertion device beamlines. The photoneutron dose equivalent rates, normalized to bremsstrahlung power, beam current, and storage ring pressure, are measured for the four targets. The photoneutron dose equivalent rates, normalized to the bremsstrahlung power and corrected for systematic variations, are given as 2.2±0.5 rem/h/W for Fe,3.0±0.5 rem/h/W for Cu, 3.8±0.5 rem/h/W for W, and 3.7±0.8 rem/h/W for Pb targets, at a distance of 0.8 m perpendicular from the target center.

Parameterization of e and γ initiated showers in the NOMAD lead-glass calorimeter

A description of the response of the NOMAD electromagnetic calorimeter to electrons and photons is discussed. In particular, the dependence of the two-dimensional shower shape on the angle and energy of the incident particle is parametrized by analytical functions. Some applications to the neutrino event reconstruction are also reported.

The HERMES Spectrometer

The HERMES experiment is collecting data on inclusive and semi-inclusive deep inelastic scattering of polarised positrons from polarised targets of H, D, and 3He. These data give information on the spin structure of the nucleon. This paper describes the forward angle spectrometer built for this purpose. The spectrometer includes numerous tracking chambers (micro-strip gas chambers, drift and proportional chambers) in front of and behind a 1.3 T.m magnetic field, as well as an extensive set of detectors for particle identification (a lead-glass calorimeter, a pre-shower detector, a transition radiation detector, and a threshold Cherenkov detector). Two of the main features of the spectrometer are its good acceptance and identification of both positrons and hadrons, in particular pions. These characteristics, together with the purity of the targets, are allowing HERMES to make unique contributions to the understanding of how the spins of the quarks contribute to the spin of the nucleon.

A study of the transverse fluctuations of hadronic showers in the NOMAD electromagnetic calorimeter

The transverse shower shape of the energy deposition of hadrons in the NOMAD lead glass calorimeter has been studied by exposing a prototype of this calorimeter to pion test beams of various momenta and incident angles. Large event-to-event fluctuations in the shower shape and significant energy depositions far from the incident hadron were observed making it difficult to associate all the deposited energy to the incident hadron that caused it. Since in the NOMAD detector the momenta of charged hadrons are measured by a magnetic spectrometer, such an association is necessary to be able to subtract from the calorimeter all the energy caused by the observed charged hadrons in order to avoid double counting. Probability functions based on the measurements have been developed to describe fluctuations of the lateral shower shape. Starting from these functions, an algorithm is developed for identifying the energy deposition associated to a charged hadron. The identification and separation of overlapping showers based on these functions is also discussed. The Monte Carlo simulation of the calorimeter reproduces the test beam data well therefore allowing the application of the algorithm at angles and momenta not studied in the test beam.

A study of the transverse fluctuations of hadronic showers in the NOMAD electromagnetic calorimeter

The transverse shower shape of the energy deposition of hadrons in the NOMAD lead glass calorimeter has been studied by exposing a prototype of this calorimeter to pion test beams of various momenta and incident angles. Large event-to-event fluctuations in the shower shape and significant energy depositions far from the incident hadron were observed making it difficult to associate all the deposited energy to the incident hadron that caused it. Since in the NOMAD detector the charged hadrons are measured by the drift chambers, such an association is necessary to be able to subtract from the calorimeter all the energy caused by the observed charged hadrons in order to avoid double counting.Probability functions based on the measurements have been developed to describe fluctuations of the lateral shower shape. An algorithm, based on these functions for identifying the energy deposition associated to a charged hadron is described.