The PAMELA Time-of-Flight system: status report

Abstract The PAMELA (Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics) satellite-borne experiment, scheduled to be launched in 2003, aboard a Soyuz TM2 rocket, is designed to provide a better understanding of the antimatter component of cosmic rays. In the following we report on the features and performances of its scintillator telescope system which will provide the primary experimental trigger and time-of-flight particle identification

A measurement of cosmic ray deuterium from 0.5–2.9 GeV/nucleon

The rare isotopes ^(2)H and ^(3)He in cosmic rays are believed to originate mainly from the interaction of high energy protons and helium with the galactic interstellar medium. The unique propagation history of these rare isotopes provides important constraints on galactic cosmic ray source spectra and on models for their propagation within the Galaxy. Hydrogen and helium isotopes were measured with the balloon-borne experiment, IMAX, which flew from Lynn Lake, Manitoba in 1992. The energy spectrum of deuterium between 0.5 and 3.2 GeV/nucleon measured by the IMAX experiment as well as previously published results of ^(3)He from the same instrument will be compared with predictions of cosmic ray galactic propagation models. The observed composition of the light isotopes is found to be generally consistent with the predictions of the standard Leaky Box Model derived to fit observations of heavier nucle

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Comparison of 3-Dimensional and 1-Dimensional Schemes in the calculation of Atmospheric Neutrinos

A 3-dimensional calculation of atmospheric neutrinos flux is presented, and the results are compared with those of a 1-dimensional one. In this study, interaction and propagation of particles is treated in a 3-dimensional way including the curvature of charged particles due to the geomagnetic field, which is assumed to be a dipole field. The purpose of this paper is limited to the comparison of calculation schemes. The updated flux value with new interaction model and primary flux model will be reported in a separate paper. Except for nearly horizontal directions, the flux is very similar to the result of 1 dimensional calculations. However, for near-horizontal directions an enhancement of the neutrino flux is seen even at energies as high as 1 GeV. The production height of neutrinos is lower than the prediction by 1-dimensional calculation for near-horizontal directions, and is a little higher for near-vertical directions. However, the difference is not evident except for near-horizontal directions.Comment: 22 pages, 15figure

The ToF and Trigger electronics of the PAMELA experiment

The PAMELA satellite-borne experiment, scheduled to be launched in 2004, is designed to provide a better understanding of the antimatter component of the cosmic rays. Its ToF scintillator system will provide the primary experimental trigger and time-of-flight particle identification. The time resolution requested is σ, < 120 ps. To fulfill the detector requirements the digitization electronics should have a time resolution ≤ 50 ps and provide a wide dynamic range for charge measurements. The peculiarity of the developed electronics arises from the need to obtain such a time resolution operating in a satellite environment, which implies low-power consumption, radiation hardness, redundancy and high reliability

Measurement of 0.25-3.2 GeV antiprotons in the cosmic radiation

The balloon-borne Isotope Matter-Antimatter Experiment (IMAX) was flown from Lynn Lake, Manitoba, Canada on 16–17 July 1992. Using velocity and magnetic rigidity to determine mass, we have directly measured the abundances of cosmic ray antiprotons and protons in the energy range from 0.25 to 3.2 GeV. Both the absolute flux of antiprotons and the antiproton/proton ratio are consistent with recent theoretical work in which antiprotons are produced as secondary products of cosmic ray interactions with the interstellar medium. This consistency implies a lower limit to the antiproton lifetime of ∼10 to the 7th yr

Systematic inference of the long-range dependence and heavy-tail distribution parameters of ARFIMA models

Long-Range Dependence (LRD) and heavy-tailed distributions are ubiquitous in natural and socio-economic data. Such data can be self-similar whereby both LRD and heavy-tailed distributions contribute to the self-similarity as measured by the Hurst exponent. Some methods widely used in the physical sciences separately estimate these two parameters, which can lead to estimation bias. Those which do simultaneous estimation are based on frequentist methods such as Whittle’s approximate maximum likelihood estimator. Here we present a new and systematic Bayesian framework for the simultaneous inference of the LRD and heavy-tailed distribution parameters of a parametric ARFIMA model with non-Gaussian innovations. As innovations we use the α-stable and t-distributions which have power law tails. Our algorithm also provides parameter uncertainty estimates. We test our algorithm using synthetic data, and also data from the Geostationary Operational Environmental Satellite system (GOES) solar X-ray time series. These tests show that our algorithm is able to accurately and robustly estimate the LRD and heavy-tailed distribution parameters

The Time of Flight Detector and Trigger for the Pamela Experiment in Space

The electronics of the Time of Flight telescope and trigger of PAMELA experiment are described. The time resolution requested by the ToF system must be less than 120 ps. The contribution of the digitization electronics is negligible if the TDC resolution is < 50 ps. The peculiarity of the developed electronics arises from the need to obtain such a time resolution associated to a wide dynamic range for charge measurements, operating in satellite environment, which implies low power consumption, radiation hardness, redundancy and high reliabilit

The Cosmic-Ray Proton and Helium Spectra measured with the CAPRICE98 balloon experiment

A new measurement of the primary cosmic-ray proton and helium fluxes from 3 to 350 GeV was carried out by the balloon-borne CAPRICE experiment in 1998. This experimental setup combines different detector techniques and has excellent particle discrimination capabilities allowing clear particle identification. Our experiment has the capability to determine accurately detector selection efficiencies and systematic errors associated with them. Furthermore, it can check for the first time the energy determined by the magnet spectrometer by using the Cherenkov angle measured by the RICH detector well above 20 GeV/n. The analysis of the primary proton and helium components is described here and the results are compared with other recent measurements using other magnet spectrometers. The observed energy spectra at the top of the atmosphere can be represented by (1.27+-0.09)x10^4 E^(-2.75+-0.02) particles (m^2 GeV sr s)^-1, where E is the kinetic energy, for protons between 20 and 350 GeV and (4.8+-0.8)x10^2 E^(-2.67+-0.06) particles (m^2 GeV nucleon^-1 sr s)^-1, where E is the kinetic energy per nucleon, for helium nuclei between 15 and 150 GeV nucleon^-1.Comment: To be published on Astroparticle Physics (44 pages, 13 figures, 5 tables

Measurement of the Abundance of Radioactive ^(10)Be and Other Light Isotopes in Cosmic Radiation up to 2 GeV Nucleon^(-1) with the Balloon-Borne Instrument Isomax

The Isotope Magnet Experiment (ISOMAX), a balloon-borne superconducting magnet spectrometer, was designed to measure the isotopic composition of the light isotopes (3 ≤ Z ≤ 8) of cosmic radiation up to 4 GeV nucleon^(-1) with a mass resolution of better than 0.25 amu by using the velocity versus rigidity technique. To achieve this stringent mass resolution, ISOMAX was composed of three major detector systems: a magnetic rigidity spectrometer with a precision drift chamber tracker in conjunction with a three-layer time-of-flight system, and two silica-aerogel Cerenkov counters for velocity determination. A special emphasis of the ISOMAX program was the accurate measurement of radioactive ^(10)Be with respect to its stable neighbor isotope ^9Be, which provides important constraints on the age of cosmic rays in the Galaxy. ISOMAX had its first balloon flight on 1998 August 4–5 from Lynn Lake, Manitoba, Canada. Thirteen hours of data were recorded during this flight at a residual atmosphere of less than 5 g cm^(-2). The isotopic ratio at the top of the atmosphere for 10Be/9Be was measured to be 0:195 ± 0:036 (statistical) ± 0:039 (systematic) between 0.26 and 1.03 GeV nucleon^(-1) and 0:317 ± 0:109 (statistical) ± 0:042 (systematic) between 1.13 and 2.03 GeV nucleon^(-1). This is the first measurement of its kind above 1 GeV nucleon^(-1). ISOMAX results tend to be higher than predictions from current propagation models. In addition to the beryllium results, we report the isotopic ratios of neighboring lithium and boron in the energy range of the time-of-flight system (up to ~1 GeV nucleon^(-1)). The lithium and boron ratios agree well with existing data and model predictions at similar energies