Measurement of the energy spectra of cosmic ray electron component and protons at ground level (original) (raw)
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Measurements of the absolute energy spectra of cosmic-ray positrons and electrons above 7�GeV
Astronomy & Astrophysics, 2002
A measurement of the energy spectra of cosmic-ray positrons and electrons was made with a balloon-borne magnetspectrometer, which was flown at a mean geomagnetic cut-off of 4.5 GV/c. The observed positron flux in the energy range 7-16 GeV is approximately an order of magnitude lower than that of electrons, as measured in other experiments at various energies. The power law spectral index of the observed differential energy spectrum of electrons is −2.89 ± 0.10 in the energy interval 7.5-47 GeV. For positrons the overall fit of the available data above 7 GeV has been considered. The spectral index is found to be −3.37 ± 0.26 and the fraction of positrons, e + /(e + + e − ), has a mean value of 0.064 ± 0.003. The world data on e + /(e + + e − ) from 0.1 to 30 GeV indicate that a plerion type electron spectrum is preferred over the other types. The trend of the presently existing high energy data also suggests a possible contribution of positrons produced at the pulsar polar cap. High resolution experiments capable of identifying positrons at least up to 100 GeV with high statistics are required to pinpoint the origin of both electrons and positrons in the cosmic radiation.
Analysis of the Spectral Intensities and Ratios of Electrons and Positrons in Cosmic Rays
The observations of the total electronic component and the positron fraction in cosmic rays by the FERMI, HESS, ATIC, and PAMELA instruments are studied with analytical propagation models, both for a set of discrete sources and for a spatially smooth source distribution. The positron fraction over the entire energy range of ~1-100 GeV is shown to fit with the nested leaky box model. We derive the spectrum of electrons in cosmic rays arising from direct acceleration by the sources and discuss the narrow spectral feature in the spectrum. Comment: 4 pages, 7 figures, to appear in Proceedings of the 31st ICRC
Precision measurements by the Alpha Magnetic Spectrometer on the International Space Station of the primary cosmic-ray electron flux in the range 0.5 to 700 GeV and the positron flux in the range 0.5 to 500 GeV are presented. The electron flux and the positron flux each require a description beyond a single power-law spectrum. Both the electron flux and the positron flux change their behavior at ∼30 GeV but the fluxes are significantly different in their magnitude and energy dependence. Between 20 and 200 GeV the positron spectral index is significantly harder than the electron spectral index. The etermination of the differing behavior of the spectral indices versus energy is a new observation and provides important information on the origins of cosmic-ray electrons and positrons.
The Astrophysical Journal, 2001
Measurements of the energy spectra of negative electrons and positrons have been performed with the High-Energy Antimatter Telescope (HEAT) in two balloon ÑightsÈ1994 May from Fort Sumner, NM, and 1995 August from Lynn Lake, Manitoba. We present the combined data set from these two Ñights, covering the energy range 1-100 GeV. We compare our data with results from other groups and discuss the data in the context of di †usive propagation models. There is some evidence that primary electrons above 10 GeV and cosmic-ray nuclei exhibit the same energy spectrum at the source, but that the source spectrum becomes harder at lower energy. Within the experimental uncertainties, the intensity of positrons is consistent with a purely secondary origin, due to nuclear interactions in interstellar space.
The Cosmic-Ray Proton and Helium Spectra between 0.4 and 200 GV
Astrophysical Journal, 1999
We report on the hydrogen nuclei (protons and deuterons) spectrum from 0.15 to 200 GeV and on the helium nuclei spectrum over the energy range from 0.2 to 100 GeV nucleon~1 at the top of the atmosphere measured by the balloon-borne experiment Cosmic Antiparticle Ring-Imaging Cerenkov Experiment (CAPRICE), which was Ñown from Lynn Lake, Manitoba, Canada, on 1994 August 8È9. We also report on the proton spectrum over the energy range from 0.15 to 4.2 GeV. The experiment used the NMSU-WiZard/CAPRICE balloon-borne magnet spectrometer equipped with a solid radiator Ring-Imaging Cerenkov (RICH) detector and a silicon-tungsten calorimeter for particle identiÐcation. This was the Ðrst time a RICH was used together with an imaging calorimeter in a balloon-borne experiment. These detectors allowed for clear particle identiÐcation, as well as excellent control of the detector efficiencies. The data were collected during 18 hr at a residual mean atmospheric depth of 3.9 g cm~2. With this apparatus 516,463 hydrogen and 32,457 helium nuclei were identiÐed in the rigidity range 0.4 to 200 GV and 1.2 to 200 GV, respectively. The observed energy spectrum at the top of the atmosphere can be represented by (1.1^0.1) ] 104 E~2.73B0.06 particles (m2 GeV sr s)~1 for hydrogen (E in GeV) between 20 and 200 GeV and (4.3^0.9) ] 102 E~2.65B0.07 particles (m2 GeV nucleon~1 sr s)~1 for helium nuclei (E in GeV nucleon~1) between 10 and 100 GeV nucleon~1. These spectra are in good agreement with other recent measurements above 10 GeV. The observed spectra Ñatten below 10 GeV due to solar modulation and are consistent with earlier measurements when solar modulation is taken into account. Between 5 and 200 GV the hydrogen to helium ratio as a function of rigidity was found to be approximately constant at 6.1^0.1.
The Cosmic-Ray Electron and Positron Spectra Measured at 1 AU during Solar Minimum Activity
Astrophysical Journal, 2000
We report on a new measurement of the cosmic-ray electron and positron spectra. The data were collected by the balloon-borne experiment CAPRICE94, which was Ñown from Lynn Lake, Canada, on 1994 August 8È9 at an altitude corresponding to 3.9 g cm~2 of average residual atmosphere. The experiment used the NMSU-WIZARD/CAPRICE94 balloon-borne magnet spectrometer equipped with a solid radiator Ring Imaging Cerenkov (RICH) detector, a time-of-Ñight system, a tracking device consisting of drift chambers and multiwire proportional chambers, and a silicon-tungsten calorimeter. This was the Ðrst time a RICH detector was used together with an imaging calorimeter in a balloon-borne experiment. A total of 3211 electrons, with a rigidity at the spectrometer between 0.3 and 30 GV, and 734 positrons, between 0.3 and 10 GV, were identiÐed with small backgrounds from other particles. The absolute energy spectra were determined in the energy region at the top of the atmosphere between 0.46 and 43.6 GeV for electrons and between 0.46 and 14.6 GeV for positrons. We found that the observed positron spectrum and the positron fraction are consistent with a pure secondary origin. A comparison of the theoretically predicted interstellar spectrum of electrons shows that the injection spectrum of primary electrons is steeper than that of the nucleonic components of cosmic rays. Furthermore, the observed electron and positron spectra can be reproduced from the interstellar spectra by a spherically symmetric model for solar modulation ; hence, the modulation is independent of the sign of the particle charge. Subject headings : balloons È cosmic rays È elementary particles È Sun : activity 653 654 BOEZIO ET AL.
The interpretation of the spectrum of energetic cosmic rays
1974
One of the most prominent and well established features in the primary energy spectrum of cosmic rays observed at the Earth is the change of slope occurring at several 10(^15) eV. A comprehensive survey of experimental EAS data is used to establish the integral size spectrum for electrons and muons at sea level and for electrons at mountain altitudes. A model for the diffusion of protons in the Galaxy is developed based on experimental observations of the structure of hydrogen in the interstellar medium and of the magnetic field strengths and their orientations in galactic space. A numerical treatment of the diffusion problem is adopted. A pre-diction is made of the primary cosmic ray proton energy spectrum at the top of the atmosphere. A survey of the data on cosmic ray primaries with energies below ~10(^11) eV obtained by balloon and satellite experiments, was used to establish the relative abundances of all cosmic rays. By assuming that the cosmic ray composition remains the same...
The Primary Proton Spectrum of Cosmic Rays Measured with Single Hadrons at Ground Level
The Astrophysical Journal, 2004
The flux of cosmic-ray-induced single hadrons near sea level has been measured with the large hadron calorimeter of the KASCADE experiment. The measurement corroborates former results obtained with detectors of smaller size if the enlarged veto of the 304 m 2 calorimeter surface is accounted for. The program CORSIKA/ QGSJET is used to compute the cosmic-ray flux above the atmosphere. Between E 0 ¼ 300 GeV and 1 PeV the primary proton spectrum can be described with a power law parameterized as dJ =dE 0 ¼ (0:15 AE 0:03)E À2:78AE0:03 0 m À2 s À1 sr À1 TeV À1. At the lower energy end the proton flux compares well with the results from recent direct measurements.
Measurement of the Positron to Electron Ratio in Cosmic Rays above 5 GeV
Astrophysical Journal, 1996
As part of a series of experiments to search for antimatter in cosmic rays, the New Mexico State University balloon-borne magnet spectrometer was configured for a flight to study positrons. Two completely new instruments, a transition radiation detector and a silicon-tungsten imaging calorimeter, were added to the magnet spectrometer. These two detectors provided a proton rejection factor better than 3 ϫ 10 4 . This instrument was flown from Fort Sumner, New Mexico, at an average depth of 4.5 g cm Ϫ2 of residual atmosphere for a period of 25 hr. We report here the measured fraction of positrons e ϩ /(e ϩ ϩ e Ϫ ) from 15 to 60 GeV at the top of the atmosphere. Our measurements do not show any compelling evidence for an increase in this ratio with energy, and our results are consistent with a constant fraction of 0.078 H 0.016 over the entire energy region. Subject headings: cosmic rays -elementary particles FIG. 1.-Schematic diagram of the TS93 apparatus L104 GOLDEN ET AL. Vol. 457
Measurement of the Positron to Electron Ratio in the Cosmic Rays above 5 GeV
The Astrophysical Journal, 1996
As part of a series of experiments to search for antimatter in cosmic rays, the New Mexico State University balloon-borne magnet spectrometer was configured for a flight to study positrons. Two completely new instruments, a transition radiation detector and a silicon-tungsten imaging calorimeter, were added to the magnet spectrometer. These two detectors provided a proton rejection factor better than 3 ϫ 10 4 . This instrument was flown from Fort Sumner, New Mexico, at an average depth of 4.5 g cm Ϫ2 of residual atmosphere for a period of 25 hr. We report here the measured fraction of positrons e ϩ /(e ϩ ϩ e Ϫ ) from 15 to 60 GeV at the top of the atmosphere. Our measurements do not show any compelling evidence for an increase in this ratio with energy, and our results are consistent with a constant fraction of 0.078 H 0.016 over the entire energy region. Subject headings: cosmic rays -elementary particles FIG. 1.-Schematic diagram of the TS93 apparatus L104 GOLDEN ET AL. Vol. 457