The sat calorimeter of the DELPHI experiment at LEP; results of a module test

The construction of an electromagnetic calorimeter using scintillating plastic fibres and lead plates is described. The calorimeter is part of the Small Angle Tagger (SAT) of the DELPHI experiment at the LEP collider, recording high-energy electrons, positrons and photons. Results from a test of a module of similar construction are presented. The module was found to have a linear energy response when exposed to electrons of 10–70 GeV, with an energy resolution given by σ/E[%] = (1.16² + (11.4/√E[GeV])²)^1/2.     

Beam test of the CsI(Tl) calorimeter for the BELLE detector at the KEK-B factory

We studied the performance of a prototype electromagnetic calorimeter for the BELLE detector at the KEK proton synchrotron for an energy range of 0.25–3.5 GeV. The prototype consisted of an array of 6 × 5 CsI(Tl) crystals with 30 cm length (16.2 radiation lengths) and about 6 cm × 6 cm cross section. The scintillation light of each CsI(Tl) crystal was read out by two large-area PIN photodiodes and charge-sensitive preamplifiers attached at the rear face of the crystal. We measured the energy and position resolution for electrons and the e/π separation for two sets of matrix configurations: one corresponded to the center and the other to the edge of the barrel calorimeter. The overall performance measured by the test proves that the prototype calorimeter is satisfactory for the use in the BELLE detector.     

A 5 in. Si(Li)/Pb sampling calorimeter telescope for observation of cosmic gamma rays in the GeV region

A 5 in. diameter Si(Li)/Pb sampling calorimeter with a depth of 28 radiation lengths (30 unit cells × 0.93 radiation lengths) has been constructed. The energy and angular resolutions of the calorimeter have been investigated using CERN SPS positron beams with energies of 10 to 147.8 GeV. The calorimeter shows good linearity over this energy region and the energy resolution is expressed well by σ_E (rms)/E = (16.9 ± 0.9)%/ √E[GeV], where E represents the incident beam energy. The angular resolution of the calorimeter for a single event is 0.3° (rms) at 80 GeV/c. The agreement between these results and Monte Carlo simulations is good.

We are showing a new design of the Si(Li)/Pb sampling calorimeter telescope (SSCT) with an angular resolution (point source localization capability) of about 0.04° (rms) for bright galactic gamma-ray sources. We believe that this telescope is a suitable detector for future observations of cosmic gamma rays in the GeV region, especially when used to search for point sources.     

Study of a BGO calorimeter using electron and hadron beams from 1 to 50 GeV

A calorimeter of 25 bismuth germanate (BGO) crystals equipped with silicon photodiode readout has been tested at the CERN SPS in the energy range 1–50 GeV. The response for electrons has been shown to be linear in this energy range and the rms resolution obtained ( ) is approximately 1%, for E > 4 GeV. The electron/pion separation was found to be better than 1:500 in the energy range 1–20 GeV. Data on lateral and longitudinal shower development were compared with the results of a Monte Carlo simulation using the SLAC-EGS program and found to be in good agreement.     

PAMELA and electrons

The 15th of June 2006, the PAMELA satellite-borne experiment was launched from the Baikonur cosmodrome and it has been collecting data since July 2006. The apparatus comprises a time-of-flight system, a silicon-microstrip magnetic spectrometer, a silicon–tungsten electromagnetic calorimeter, an anticoincidence system, a shower tail counter scintillator and a neutron detector. The combination of these devices allows precision studies of the charged cosmic radiation to be conducted over a wide energy range (100 MeV–100's GeV) with high statistics. The measurement of the positron to electron fraction and of the electron energy spectrum in order to search for exotic sources, such as dark matter particle annihilations, are within the PAMELA primary scientific goal.     

Design of a polarized positron source for linear colliders

We propose a design of a polarized positron source for linear colliders. The design is based on electron–positron pair creation from polarized γ-rays which are produced by Compton scattering of circularly polarized laser light off a high-energy electron beam. Polarized positrons are created from those γ-rays incident on a thin conversion target. A future linear collider of the TeV-energy region requires an extraordinary large number of positrons (1×10¹⁰ positrons/bunch) in a multi-bunch time structure. To meet these requirements, our design employs a high-current, low-emittance electron beam of 5.8 GeV, 10 CO₂ lasers, and 200 laser–electron collision-points. At each collision point, a pair of specially designed parabolic mirrors is installed to achieve efficient head-on collisions. This system allows us to produce high-intensity polarized γ-rays, which effectively generate high-intensity polarized positrons with the magnitude of polarization greater than 50%.     

Experimental results from a sandwich calorimeter using U absorbers and 0.25 m of Si active area

The electromagnetic section of a hadronic calorimeter, consisting of uranium absorbers and of silicon sampling units with an active area of 0.25 m², was investigated. The overall performance of the silicon detectors and especially developed associated electronics, seems to be stable and reliable. During a four-week run at the t₉, CERN-PS (Proton Synchrotron) electron beam (energies of 2 to 6 GeV), no variation of energy calibration of the calorimeter was observed. The energy resolution for electromagnetic showers was found to be about , where E is the energy of the incoming electron and τ is the number of radiation lengths of passive material interspaced between two active samplers, for a calorimeter depth of 15.6 X₀ (radiation lengths), with Si samplers depleted to 200 μm. The fiberglass supports of the silicon mosaics cause a reduction of energy response to electromagnetic showers. It can be exploited to equalize the response of a Si/U hadronic calorimeter to incoming electrons and hadrons.     

A high-granularity scintillator calorimeter readout with silicon photomultipliers

We report on the design, construction and performance of a prototype for a high-granularity tile hadronic calorimeter for a future international linear collider detector. Scintillating tiles are read out via wavelength-shifting fibers that guide the scintillation light to a novel photodetector, the silicon photomultiplier. A prototype has been tested using a positron test beam at DESY. The results are compared with a reference prototype calorimeter equipped with multichannel vacuum photomultipliers. Detector calibration, noise, linearity and stability are discussed, and the energy response in a 1–6 GeV positron beam is compared with simulations. The present results demonstrate that the silicon photomultiplier is well-suited as photodetectors in calorimeters and thus has been selected for the construction of a calorimeter prototype to operate in hadron beams.     

Response functions of Si detectors to monoenergetic electrons and positrons in the energy range 0.8–3.5 MeV

The response functions of Si surface barrier detectors (depletion depth: 2 mm, active area: 200 mm²) to monoenergetic electrons and positrons have been measured in the energy range 0.8–3.5 MeV at the Giessen electron linear accelerator. Lower peak-to-total ratios were observed in the positron response functions compared to electrons. The measured response functions were compared with Monte Carlo simulations enabling a separation of the individual contributions to the response function such as: total energy loss, backscattering, transmission, bremsstrahlung emission. A parametrization of the response function for electrons is given, which allows a reliable approximation of the response function in the investigated energy range.     

Response of the CALICE Si-W electromagnetic calorimeter physics prototype to electrons

A prototype silicon–tungsten electromagnetic calorimeter (ECAL) for an international linear collider (ILC) detector was installed and tested during summer and autumn 2006 at CERN. The detector had 6480 silicon pads of dimension . Data were collected with electron beams in the energy range 6–45 GeV. The analysis described in this paper focuses on electromagnetic shower reconstruction and characterises the ECAL response to electrons in terms of energy resolution and linearity. The detector is linear to within approximately the 1% level and has a relative energy resolution of . The spatial uniformity and the time stability of the ECAL are also addressed.     

Precision measurement of energy and position resolutions of the BTeV electromagnetic calorimeter prototype

The energy dependence of the energy and position resolutions of the electromagnetic calorimeter prototype made of lead tungstate crystals produced in Bogoroditsk (Russia) and Shanghai (China) is presented. These measurements were carried out at the Protvino accelerator using a 1–45 GeV electron beam. The crystals were coupled to photomultiplier tubes. The dependence of energy and position resolutions on different factors as well as the measured electromagnetic shower lateral profile are presented.     

Performance of the ATLAS electromagnetic calorimeter barrel module 0

The construction and performance of the barrel pre-series module 0 of the future ATLAS electromagnetic calorimeter at the LHC is described. The signal reconstruction and performance of ATLAS-like electronics has been studied. The signal to noise ratio for muons has been found to be 7.11±0.07. An energy resolution of better than (sampling term) has been obtained with electron beams of up to 245 GeV. The uniformity of the response to electrons in an area of Δη×Δφ=1.2×0.075 has been measured to be better than 0.8%.     

The ZEUS forward plug calorimeter with lead–scintillator plates and WLS fiber readout

A Forward Plug Calorimeter (FPC) for the ZEUS detector at HERA has been built as a shashlik lead–scintillator calorimeter with wave length shifter fiber readout. Before installation it was tested and calibrated using the X5 test beam facility of the SPS accelerator at CERN. Electron, muon and pion beams in the momentum range of 10–100 GeV/c were used. Results of these measurements are presented as well as a calibration monitoring system based on a ⁶⁰Co source.     

WA78 calorimeter test results

The results from the WA78 uranium calorimeter in the momentum range 5–40 GeV are discussed. Data were also taken implementing the detector with a small electromagnetic uranium calorimeter upstream the existing hadronic section.     

Performance of an electromagnetic liquid krypton calorimeter based on a ribbon electrode tower structure

The NA48 collaboration is preparing a new experiment at CERN aiming to study CP violation in the K⁰- system with an accuracy of 2 × 10⁻⁴ in the parameter e(ε′/ε). Decays in two π⁰'s will be recorded by a quasi-homogeneous liquid krypton calorimeter. A liquid krypton calorimeter has been chosen to combine good energy, position and time resolution with precise charge calibration and long-term stability. The prototype calorimeter incorporating the final design of the electrode read-out structure is presented in this paper. An energy resolution of 3.5%/√E with a constant term smaller than 0.5% has been obtained. The time resolution was found to be better than 300 ps above 15 GeV.     

Performance of the ATLAS electromagnetic calorimeter end-cap module 0

The construction and beam test results of the ATLAS electromagnetic end-cap calorimeter pre-production module 0 are presented. The stochastic term of the energy resolution is between 10% and 12.5% GeV^1/2 over the full pseudorapidity range. Position and angular resolutions are found to be in agreement with simulation. A global constant term of 0.6% is obtained in the pseudorapidity range 2.5<η<3.2 (inner wheel).     

Identification of the light nuclei component of cosmic rays with the PAMELA experiment

The PAMELA (Payload for Antimatter Matter Exploration and Light nuclei Astrophysics) experiment is a satellite-borne apparatus that will make long duration measurements of the cosmic radiation with a particular focus on antiparticles and light nuclei. The main scientific objective of the PAMELA mission is to investigate the nature of the dark matter that pervades the universe, the apparent absence of cosmological antimatter, the origin and evolution of matter in the Galaxy. Specifically PAMELA will measure the cosmic-ray antiproton and positron spectra over the largest energy range ever achieved and will search for antinuclei with unprecedented sensitivity. Furthermore, it will measure the light nuclear component of cosmic rays from Hydrogen up to Oxygen in the interval 200 MeV/n–150 GeV/n. Accurate measurements of the elemental composition are required in order to understand the origin, propagation and lifetime of the cosmic radiation. The primary cosmic rays (e.g. C, N and O), produced at the sources, propagate through the interstellar medium giving information about the composition at the source. Secondary elements (e.g. Li, Be, and B) are tracers of amount of matter traversed by the cosmic rays. The relative abundances of the constituents of galactic cosmic rays provide information about cosmic-ray transport within the Galaxy. PAMELA consists of a magnetic spectrometer, a Time-of-Flight and trigger system, an electromagnetic calorimeter, an anticoincidence system, a shower tail catcher scintillator and a neutron detector. The combination of these devices allows antiparticles to be reliably identified from a large background of other charged particles. This paper reviews the capability of the PAMELA subdetectors to identify light nuclei. Analysis techniques to discriminate light-charged particles will be presented.     

Measurement of the time development of particle showers in a uranium scintillator calorimeter

We report on the time evolution of particle showers, as measured in modules of the uranium-scintillator barrel calorimeter of the ZEUS detector. The time development of hadronic showers differs significantly from that of electromagnetic showers, with about 40% of the response to hadronic showers arising from energy depositions which occur late in the shower development. The degree of compensation and the hadronic energy resolution were measured as a function of integration time, giving a value of for a gate width of 100 ns. The possibilities for electron-hadron separation based on the time structure of the shower were studied, with pion rejection factors in excess of 100 being achieved for electron efficiencies greater than 60%. The custom electronics used to perform these measurements samples the calorimeter signal at close to 60 MHz, stores all samples for a period of over 4 μs using analog switched capacitor pipelines, and digitizes the samples for triggered events with 12-bit ADCs.     

Interactions of 200 GeV muons in an electromagnetic streamer tube calorimeter

We have investigated the response of an electromagnetic streamer tube calorimeter to 200 GeV muons. Muons undergo electromagnetic interactions in the absorber plates and produce electrons, photons or electron pairs the energy of which is measured by the calorimeter. Occasionally also catastrophic energy losses occur, so that in these very rare cases muons could even be misinterpreted as electrons.     

Simulations of a thin sampling calorimeter with GEANT/FLUKA

The Advanced Cosmic-ray Composition Experiment for the Space Station (ACCESS) will investigate the origin, composition and acceleration mechanism of cosmic rays by measuring the elemental composition of the cosmic rays up to 10¹⁵ eV. These measurements will be made with a thin ionization calorimeter and a transition radiation detector. This paper reports studies of a thin sampling calorimeter concept for the ACCESS thin ionization calorimeter. For the past year, a Monte Carlo simulation study of a thin sampling calorimeter (TSC) design has been conducted to predict the detector performance and to design the system for achieving the ACCESS scientific objectives. Simulation results show that the detector energy resolution function resembles a Gaussian distribution and the energy resolution of TSC is about 40%. In addition, simulations of the detector's response to an assumed broken power law cosmic ray spectrum in the region where the ‘knee’ of the cosmic ray spectrum is believed to occur have been conducted and clearly show that a thin sampling calorimeter can provide sufficiently accurate estimates of the spectral parameters to meet the science requirements of ACCESS.