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Precision measurements of Z, W, and H decays at the next generation of circular lepton colliders will require excellent energy resolution for both electromagnetic and hadronic showers. The resolution is limited by event-to-event fluctuations in the shower development, especially in the hadronic system. Compensating for this effect can greatly improve the achievable energy resolution. Furthermore, the resolution can benefit greatly from the use of particle-flow algorithms, which requires the calorimeters to have a high granularity. The approach of dual-readout calorimetry has emerged as a candidate to fulfil both of these requirements by allowing to reconstruct the fluctuations in the shower development event-by-event and offering a high transverse granularity. An important benchmark of such a calorimeter is the electromagnetic energy resolution; a prototype of the IDEA calorimeter has been built for use in testbeams. In parallel, a simulation of this prototype has been developed in Geant4 for a testbeam environment. Here, we outline how this simulation was used to study the electromagnetic energy resolution and conclude that a resolution of 14 % / E is achievable. [ABSTRACT FROM AUTHOR]

Precision measurements of Z, W, and H decays at the next generation of circular lepton colliders will require excellent energy resolution for both electromagnetic and hadronic showers. The resolution is limited by event-to-event fluctuations in the shower development, especially in the hadronic system. Compensating for this effect can greatly improve the achievable energy resolution. Furthermore, the resolution can benefit greatly from the use of particle-flow algorithms, which requires the calorimeters to have a high granularity. The approach of dual-readout calorimetry has emerged as a candidate to fulfil both of these requirements by allowing to reconstruct the fluctuations in the shower development event-by-event and offering a high transverse granularity. An important benchmark of such a calorimeter is the electromagnetic energy resolution; a prototype of the IDEA calorimeter has been built for use in testbeams. In parallel, a simulation of this prototype has been developed in Geant4 for a testbeam environment. Here, we outline how this simulation was used to study the electromagnetic energy resolution and conclude that a resolution of 14%/E is achievable.

Hundreds of concurrent collisions per bunch crossing are expected at future hadron colliders. Precision timing calorimetry has been advocated as a way to mitigate the pileup effects and, thanks to their excellent time resolution, microchannel plates (MCPs) are good candidate detectors for this goal. We report on the response of MCPs, used as secondary emission detectors, to single relativistic particles and to electromagnetic showers. Several prototypes, with different geometries and characteristics, were exposed to particle beams at the INFN-LNF Beam Test Facility and at CERN. Their time resolution and efficiency are measured for single particles and as a function of the multiplicity of particles. Efficiencies between 50% and 90% to single relativistic particles are reached, and up to 100% in presence of a large number of particles. Time resolutions between 20 ps and 30 ps are obtained. [ABSTRACT FROM AUTHOR]

I-MCP is an R&D project aimed at the exploitation of secondary emission of electrons from the surface of micro-channel plates (MCP) for single ionizing particles and fast timing of showers in high rate environments. Results from tests with electrons with energies up to 50 GeV of MCP devices with different characteristics are presented. In particular detection efficiency and time resolution are measured for a range of MCP prototypes: different MCP channel diameter and layers configuration are studied. Devices operated in I-MCP configuration, where the particle detection proceed through direct ionization of the MCP layers, are studied in comparison with the more usual PMT-MCP configuration. The results show efficiencies up to 70% for single charge particle detection for I-MCP devices with a time resolution of about 40 ps. The efficiency raise to 100% in response to high energy electromagnetic showers. [ABSTRACT FROM AUTHOR]

The results of cosmic-muon calibration of the multichannel lead-scintillation 'sandwich'-type spectrometer-telescope intended for operation in high-intensity photon and electron beams, capable of determining the beam energy and forming intrinsic trigger, are presented. It was found that the relative energy resolution at an average energy release by cosmic muons in the spectrometer of ∼26 MeV is from 7.5% to 23% depending on the internal and external trigger version. [ABSTRACT FROM AUTHOR]

We report on the response of microchannel plates (MCPs) to single relativistic particles and to electromagnetic showers. Particle detection by means of secondary emission of electrons at the MCP surface has long been proposed and is used extensively in ion time-of-flight mass spectrometers. What has not been investigated in depth is their use to detect the ionizing component of showers. The time resolution of MCPs exceeds anything that has been previously used in calorimeters and, if exploited effectively, could aid in the event reconstruction at high luminosity colliders. Several prototypes of photodetectors with the amplification stage based on MCPs were exposed to cosmic rays and to 491 MeV electrons at the INFN-LNF Beam-Test Facility. The time resolution and the efficiency of the MCPs are measured as a function of the particle multiplicity, and the results used to model the response to high-energy showers. [ABSTRACT FROM AUTHOR]

Detectors proposed for the International Linear Collider (ILC) incorporate a tungsten sampling calorimeter (‘BeamCal’) intended to reconstruct showers of electrons, positrons and photons that emerge from the interaction point of the collider with angles between 5 and 50 milliradians. For the innermost radius of this calorimeter, radiation doses at shower-max are expected to reach 100 MRad per year, primarily due to minimum-ionizing electrons and positrons that arise in the induced electromagnetic showers of e+e− ‘beamstrahlung’ pairs produced in the ILC beam–beam interaction. However, radiation damage to calorimeter sensors may be dominated by hadrons induced by nuclear interactions of shower photons, which are much more likely to contribute to the non-ionizing energy loss that has been observed to damage sensors exposed to hadronic radiation. We report here on the results of SLAC Experiment T-506, for which several different types of silicon diode sensors were exposed to doses of radiation induced by showering electrons of energy 3.5–10.6 GeV. By embedding the sensor under irradiation within a tungsten radiator, the exposure incorporated hadronic species that would potentially contribute to the degradation of a sensor mounted in a precision sampling calorimeter. Depending on sensor technology, efficient charge collection was observed for doses as large as 220 MRad. [ABSTRACT FROM AUTHOR]

Cosmic-ray calibration of the 4-channel lead scintillation monitor with internal trigger shows that the consideration of only coinciding signals of counters placed in the monitor depth and detecting the final part of the high-energy photon shower, with signals of any other counters at the monitor top, detecting both the initial part of the high-energy photon shower and low-energy background photons, decreases the number of detected coincidences by a factor of 2-4. An increase in the number of such coincidences when using the monitor in the setup for studying neutral pion photoproduction on nuclei in the photon beam of the labeling system of the 'PAKHRA' accelerator of the Lebedev Physical Institute makes it possible to separate the high-energy electromagnetic shower from the low-energy background and to monitor the beam photon energy. [ABSTRACT FROM AUTHOR]

Abstract: Monte Carlo simulations of electromagnetic particle interactions and transport by FLUKA and PENELOPE were compared. 10keV to 10MeV incident photon beams impinged a LYSO crystal and a soft-tissue phantom. Central-axis as well as off-axis depth doses agreed within 1s.d.; no systematic under- or over-estimate of the pulse height spectra was observed from 100keV to 10MeV for both materials, agreement was within 5%. Simulation of photon and electron transport and interactions at this level of precision and reliability is of significant impact, for instance, on treatment monitoring of hadrontherapy where a code like FLUKA is needed to simulate the full suite of particles and interactions (not just electromagnetic). At the interaction-by-interaction level, apart from known differences in condensed history techniques, two-quanta positron annihilation at rest was found to differ between the two codes. PENELOPE produced a 511keV sharp line, whereas FLUKA produced visible acolinearity, a feature recently implemented to account for the momentum of shell electrons. [Copyright &y& Elsevier]

The experimental results of the study of orientation dependences of the response of a composite Cherenkov shower spectrometer with a converter made of a 1-mm tungsten crystal oriented along the 〈111〉 axis at an electron energy of 28 GeV and two converter temperatures, 293 and 77 K, are presented. The parameters of the cascade curve of the shower development are varied depending on the orientation angle and crystal temperature. It is found that there is a point S in the cascade curve of the shower development in the spectrometer, at which all cascade curves intersect at any converter orientation. The position of this point in the spectrometer depth depends on the converter temperature. [ABSTRACT FROM AUTHOR]

A recently published article in Science [A. Cho, Science, 318(5852), 896 (2007)] by the Pierre Auger Laboratory has helped pinpoint the source of ultrahigh energy cosmic rays, which are the most energetic particles known in the universe. The sources found indicate support for the “active galactic nuclei” theory, which is that the ultrahigh energy cosmic rays come from supermassive black holes found at the centers of galaxies. The Pierre Auger Observatory (website: AUGER EXPERIMENT, www.auger.org) records the extensive air showers through an array of 1600 particle detectors placed 1.5 km apart in a grid spread across 3000 km2. The window of TeV gamma-ray astrophysics was opened less than 2 decades ago, when the Crab Nebula was detected for the first time. After several years of development, the technique used by imaging atmospheric Cherenkov telescopes such as HESS and MAGIC is now allowing to conduct sensitive observations in the TeV regime. Water Cherenkov instruments such as Milagro are also providing results. Different types of extragalactic and galactic sources have been detected, showing a variety of interesting phenomena that are boosting theory in very high energy gamma-ray astrophysics. Here I review basic cosmic rays, the detection methods, and then present a simulation study of the gamma-ray astronomy at PeV energies—phase 3 (GRAPES3) experiment. GRAPES-3 is a scintillator detector array equipped with a muon detector tracker at Ooty, India. The capabilities of the array can be enhanced by changing the detector separation, etc. This can reduce the energy threshold (Eth), improve the angular resolution of the array, and hence improve the significance that the array can get from a gamma-ray source. This makes the array suitable to be used for gamma-ray source detection and studies. In the present article a study of the effect of reduction in detector separation, on the performance of the array, using simulation techniques has been presented. Simulation shows that reducing the detector separation by a factor of 2 results in a factor of 2 reduction in Eth. It also gives direction of study for further improvement in the angular resolution and significance, specifically from a Crab Nebula-like spectrum. [ABSTRACT FROM AUTHOR]

Abstract: The signals from high-Z scintillating crystals such as PbWO4 and BGO contain a significant Cherenkov component. We investigate methods to determine the contribution of Cherenkov light to the signals generated by high-energy electrons and pions (mips), both statistically and event-by-event. These methods are based on differences in the spectra, the time structure and/or the directionality of the two types of light. The electron signals, and their composition, are also analyzed as a function of the age (or depth) of the shower. [Copyright &y& Elsevier]

The success of scattering muon tomography has prompted us to explore cosmic ray flux attenuation, electro-magnetic shower induction, and muonic X-ray emission as additional means for the non-destructive assay of small and medium size objects. We report on the value of the signatures of these processes as an adjunct to multiple scattering muon tomography. We discuss our experiments and the Monte-Carlo calculations of these processes, the type of information that can be drawn from their signatures, the cost and the value of this information. We discuss the general requirements for detector systems to make use of cosmic ray flux attenuation, induction of electro-magnetic showers, and muonic X-rays in muon tomography. We find that the attenuation of the cosmic ray flux allows for the inference of the density distribution for objects of automobile size and smaller with exposure times of order a few minutes. Our preliminary experiments and calculations have shown that using muonic X-rays to identify composition is exceedingly difficult, requiring months of exposure. Our experiments are not yet sensitive enough to detect muonic x-rays at the rates expected from previous accelerator experiments. [ABSTRACT FROM AUTHOR]

Abstract: Electromagnetic shower development in a copper-based fiber calorimeter is studied by simultaneously measuring the scintillation light and the Cherenkov light generated in this process. We report on the energy resolution, the signal linearity and the dependence of the response function on the impact point and the angle of incidence.The electrons range in energy from 8 to 200GeV. Differences observed between the results from the two types of signals are presented and interpreted. [Copyright &y& Elsevier]

Estimates of the transverse development of anomalous electromagnetic showers induced by 26-GeV electrons and oriented along the 〈111〉 axis in tungsten, tungstate, and garnet crystals show the differences of shower development profiles from similar profiles of standard shower development. The Moliere length estimates are ∼8 X, ∼7.5 X, and ∼6 X or ∼28 mm, ∼67 mm, and 87 mm, respectively. [ABSTRACT FROM AUTHOR]

It is shown that the average charged particle multiplicity in electromagnetic showers induced by γ-rays with energies of 9-26 GeV in the tungsten crystal 1 mm thick ( T = 77 K) oriented along the 〈111〉 axis approximately twofold increases in comparison with a misoriented crystal. [ABSTRACT FROM AUTHOR]

Correctly identifying the nature and properties of outgoing particles from high energy collisions at the Large Hadron Collider is a crucial task for all aspects of data analysis. Classical calorimeter-based classification techniques rely on shower shapes — observables that summarize the structure of the particle cascade that forms as the original particle propagates through the layers of material. This work compares shower shape-based methods with computer vision techniques that take advantage of lower level detector information. In a simplified calorimeter geometry, our DenseNet-based architecture matches or outperforms other methods on e + - γ and e + - π + classification tasks. In addition, we demonstrate that key kinematic properties can be inferred directly from the shower representation in image format. [ABSTRACT FROM AUTHOR]