2,143 research outputs found
Measurements of Atmospheric Antiprotons
We measured atmospheric antiproton spectra in the energy range 0.2 to 3.4
GeV, at sea level and at balloon altitude in the atmospheric depth range 4.5 to
26 g/cm^2. The observed energy spectra, including our previous measurements at
mountain altitude, were compared with estimated spectra calculated on various
assumptions regarding the energy distribution of antiprotons that interacted
with air nuclei.Comment: Accepted for publication in PL
Search for Cosmic-Ray Antideuterons
We performed a search for cosmic-ray antideuterons using data collected
during four BESS balloon flights from 1997 to 2000. No candidate was found. We
derived, for the first time, an upper limit of 1.9E-4 (m^2 s sr
GeV/nucleon)^(-1) for the differential flux of cosmic-ray antideuterons, at the
95% confidence level, between 0.17 and 1.15 GeV/nucleon at the top of the
atmosphere.Comment: 4 pages, 3 figures, submitted to Phys. Rev. Let
Measurement of cosmic-ray low-energy antiproton spectrum with the first BESS-Polar Antarctic flight
The BESS-Polar spectrometer had its first successful balloon flight over
Antarctica in December 2004. During the 8.5-day long-duration flight, almost
0.9 billion events were recorded and 1,520 antiprotons were detected in the
energy range 0.1-4.2 GeV. In this paper, we report the antiproton spectrum
obtained, discuss the origin of cosmic-ray antiprotons, and use antiprotons to
probe the effect of charge sign dependent drift in the solar modulation.Comment: 18 pages, 1 table, 5 figures, submitted to Physics Letters
Measurement of the cosmic-ray antiproton spectrum at solar minimum with a long-duration balloon flight over Antarctica
The energy spectrum of cosmic-ray antiprotons from 0.17 to 3.5 GeV has been
measured using 7886 antiprotons detected by BESS-Polar II during a
long-duration flight over Antarctica near solar minimum in December 2007 and
January 2008. This shows good consistency with secondary antiproton
calculations. Cosmologically primary antiprotons have been investigated by
comparing measured and calculated antiproton spectra. BESS-Polar II data show
no evidence of primary antiprotons from evaporation of primordial black holes.Comment: 4 pages, 4 figures, submitted to Physical Review Letter
Measurements of 0.2 to 20 GeV/n cosmic-ray proton and helium spectra from 1997 through 2002 with the BESS spectrometer
We measured low energy cosmic-ray proton and helium spectra in the kinetic
energy range 0.215 - 21.5 GeV/n at different solar activities during a period
from 1997 to 2002. The observations were carried out with the BESS spectrometer
launched on a balloon at Lynn Lake, Canada. A calculation for the correction of
secondary particle backgrounds from the overlying atmosphere was improved by
using the measured spectra at small atmospheric depths ranging from 5 through
37 g/cm^2. The uncertainties including statistical and systematic errors of the
obtained spectra at the top of atmosphere are 5-7 % for protons and 6-9 % for
helium nuclei in the energy range 0.5 - 5 GeV/n.Comment: 27 pages, 7 Tables, 9 figures, Submitted to Astroparticle Physic
Measurement of Low-Energy Cosmic-Ray Antiprotons at Solar Minimum
The absolute fluxes of the cosmic-ray antiprotons at solar minimum are
measured in the energy range 0.18 to 1.4 GeV, based on 43 events unambiguously
detected in BESS '95 data. The resultant energy spectrum appears to be flat
below 1 GeV, compatible with a possible admixture of primary antiproton
component with a soft energy spectrum, while the possibility of secondary
antiprotons alone explaining the data cannot be excluded with the present
accuracy. Further improvement of statistical accuracy and extension of the
energy range are planned in future BESS flights.Comment: REVTeX, 4 pages including 4 eps figures. Submitted to PR
Measurements of Proton, Helium and Muon Spectra at Small Atmospheric Depths with the BESS Spectrometer
The cosmic-ray proton, helium, and muon spectra at small atmospheric depths
of 4.5 -- 28 g/cm^2 were precisely measured during the slow descending period
of the BESS-2001 balloon flight. The variation of atmospheric secondary
particle fluxes as a function of atmospheric depth provides fundamental
information to study hadronic interactions of the primary cosmic rays with the
atmosphere.Comment: 21 pages, 11 figures, 4 table
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