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

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

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

Simulation of Atmospheric Muon and Neutrino Fluxes with CORSIKA

The fluxes of atmospheric muons and neutrinos are calculated by a three dimensional Monte Carlo simulation with the air shower code CORSIKA using the hadronic interaction models DPMJET, VENUS, GHEISHA, and UrQMD. For the simulation of low energy primary particles the original CORSIKA has been extended by a parametrization of the solar modulation and a microscopic calculation of the directional dependence of the geomagnetic cut-off functions. An accurate description for the geography of the Earth has been included by a digital elevation model, tables for the local magnetic field in the atmosphere, and various atmospheric models for different geographic latitudes and annual seasons. CORSIKA is used to calculate atmospheric muon fluxes for different locations and the neutrino fluxes for Kamioka. The results of CORSIKA for the muon fluxes are verified by an extensive comparison with recent measurements. The obtained neutrino fluxes are compared with other calculations and the influence of the hadronic interaction model, the geomagnetic cut-off and the local magnetic field on the neutrino fluxes is investigated.Comment: revtex, 19 pages, 19 Postscript figures, submitted to Phys. Rev.

^(10)Be/^9Be ratio up to 1.0 GeV/nucleon measured in the ISOMAX 98 balloon flight

The Isotope Magnet Experiment, ISOMAX, a balloon-borne superconducting magnet spectrometer was built with the capability to measure the isotopic composition of the light isotopes (3 ≤ Z ≤ 8) of the cosmic radiation up to 4 GeV/nucleon by using the β vs. rigidity technique with a mass resolution better than 0.25 amu, employing a combination of time-of-flight (TOF) system and silica-aerogel Cherenkov counters for the velocity determination. One of the primary scientific goals of ISOMAX was the accurate measurement of radioactive 10 Be with respect to its stable neighbor isotope 9 Be conveying information on the age of the cosmic rays in the galaxy. ISOMAX had its first flight on August 4-5, 1998, from Lynn Lake, Manitoba, Canada. It provided 13 h of data with a residual atmosphere of less than 5 g/cm^2 . This paper reports the results of the beryllium ratio 10 Be/9 Be = 0.195 ± 0.036 at the top of atmosphere in the energy range from 0.261 - 1.030 GeV/nucleon using the TOF in the 1998 flight. The high energy results of the beryllium ratio up to 2 GeV/nucleon in the Cherenkov regime as well as the lithium results in the TOF energy range are also reported in these proceedings

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

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

The Cosmic Ray ^3He/^4He Ratio from 200 MeV per Nucleon^(-1) to 3.7 GeV per Nucleon^(-1)

The abundances of cosmic-ray helium isotopes between 0.2 and 3.7 GeV nucleon^(-1) were measured by the Isotope Matter Antimatter Experiment (IMAX) during a flight from Lynn Lake, Manitoba, Canada on 1992 July 16-17. The IMAX balloon-borne magnetic spectrometer realized a direct measurement of the charge, the velocity, and the rigidity of cosmic rays using plastic scintillators, a high-resolution time-of-flight system, and two silica-aerogel Cerenkov counters in conjunction with a drift chamber/multiwire proportional chamber tracking system. About 75,000 helium isotopes are identified by their mass using the velocity versus magnetic rigidity technique. The measured ^3He/^4He ratios are corrected to the top of the atmosphere, and a comparison with previous data is given. The observed isotopic composition is found to be generally consistent with the predictions of a standard leaky box model of cosmic-ray transport in the Galaxy

Measurement of the Absolute Proton and Helium Flux at the Top of the Atmosphere using IMAX

The balloon-borne experiment "IMAX" launched from Lynn Lake, Canada in 1992 has been used to measure the cosmic ray proton and helium spectra from 0.2 GeV/n to about 200 GeV/n. The IMAX apparatus was designed to search for antiprotons and light isotopes using a superconducting magnet spectrometer with ancillary scintillators, time-of-flight, and aerogel cherenkov detectors. Using redundant detectors an extensive examination of the instrument efficiency was carried out. We present here the absolute spectra of protons and helium corrected to the top of the atmosphere

A New Approach to Searching for Dark Matter Signals in Fermi-LAT Gamma Rays

Several cosmic ray experiments have measured excesses in electrons and positrons, relative to standard backgrounds, for energies from ~ 10 GeV - 1 TeV. These excesses could be due to new astrophysical sources, but an explanation in which the electrons and positrons are dark matter annihilation or decay products is also consistent. Fortunately, the Fermi-LAT diffuse gamma ray measurements can further test these models, since the electrons and positrons produce gamma rays in their interactions in the interstellar medium. Although the dark matter gamma ray signal consistent with the local electron and positron measurements should be quite large, as we review, there are substantial uncertainties in the modeling of diffuse backgrounds and, additionally, experimental uncertainties that make it difficult to claim a dark matter discovery. In this paper, we introduce an alternative method for understanding the diffuse gamma ray spectrum in which we take the intensity ratio in each energy bin of two different regions of the sky, thereby canceling common systematic uncertainties. For many spectra, this ratio fits well to a power law with a single break in energy. The two measured exponent indices are a robust discriminant between candidate models, and we demonstrate that dark matter annihilation scenarios can predict index values that require "extreme" parameters for background-only explanations.Comment: v1: 11 pages, 7 figures, 1 table, revtex4; v2: 13 pages, 8 figures, 1 table, revtex4, Figure 4 added, minor additions made to text, references added, conclusions unchanged, published versio