Cosmic-Ray Positrons: Are There Primary Sources?

Cosmic rays at the Earth include a secondary component originating in collisions of primary particles with the diffuse interstellar gas. The secondary cosmic rays are relatively rare but carry important information on the Galactic propagation of the primary particles. The secondary component includes a small fraction of antimatter particles, positrons and antiprotons. In addition, positrons and antiprotons may also come from unusual sources and possibly provide insight into new physics. For instance, the annihilation of heavy supersymmetric dark matter particles within the Galactic halo could lead to positrons or antiprotons with distinctive energy signatures. With the High-Energy Antimatter Telescope (HEAT) balloon-borne instrument, we have measured the abundances of positrons and electrons at energies between 1 and 50 GeV. The data suggest that indeed a small additional antimatter component may be present that cannot be explained by a purely secondary production mechanism. Here we describe the signature of the effect and discuss its possible origin.Comment: 15 pages, Latex, epsfig and aasms4 macros required, to appear in Astroparticle Physics (1999

TeV Particle Astrophysics II: Summary comments

A unifying theme of this conference was the use of different approaches to understand astrophysical sources of energetic particles in the TeV range and above. In this summary I review how gamma-ray astronomy, neutrino astronomy and (to some extent) gravitational wave astronomy provide complementary avenues to understanding the origin and role of high-energy particles in energetic astrophysical sources.Comment: 6 pages, 4 figures; Conference summary talk for "TeV Particle Astrophysics II" at University of Wisconsin, Madison, 28-31 August 200

Measurement of the Cosmic-Ray Antiproton to Proton Abundance Ratio between 4 and 50 GeV

We present a new measurement of the antiproton to proton abundance ratio, pbar/p, in the cosmic radiation. The HEAT-pbar instrument, a balloon borne magnet spectrometer with precise rigidity and multiple energy loss measurement capability, was flown successfully in Spring 2000, at an average atmospheric depth of 7.2 g/cm^2. A total of 71 antiprotons were identified above the vertical geomagnetic cut-off rigidity of 4.2 GV. The highest measured proton energy was 81 GeV. We find that the pbar/p abundance ratio agrees with that expected from a purely secondary origin of antiprotons produced by primary protons with a standard soft energy spectrum.Comment: 4 pages, 3 figures; accepted for publication in PR

First measurements of cosmic-ray nuclei at high energy with CREAM

36siCerenkov detector; Charge; Cosmic rays; Energy spectrum; TRDreservedThe balloon-borne cosmic-ray experiment CREAM-I (Cosmic-Ray Energetics And Mass) recently completed a successful 42-day flight during the 2004–2005 NASA/NSF/NSBF Antarctic expedition. CREAM-I combines an imaging calorimeter with charge detectors and a precision transition radiation detector (TRD). The TRD component of CREAM-I is targeted at measuring the energy of cosmic-ray particles with charges greater than Z ∼ 3. A central science goal of this effort is the determination of the ratio of secondary to primary nuclei at high energy. This measurement is crucial for the reconstruction of the propagation history of cosmic rays, and consequently for the determination of their source spectra. First scientific results from this instrument are presented.mixedS.P. WAKELY; H.S. AHN; P. ALLISON; M.G. BAGLIESI; J.J. BEATTY; G. BIGONGIARI; P. BOYLE; T.J. BRANDT; J.T. CHILDERS; N.B. CONKLIN; S. COUTU; M.A. DUVERNOIS; O. GANEL; J.H. HAN; J.A. JEON; K.C. KIM; M.H. LEE; L. LUTZ; P. MAESTRO; A. MALININE; P.S. MARROCCHESI; S. MINNICK; S.I. MOGNET; S.W. NAM; S. NUTTER; I.H. PARK; J.H. PARK; N.H. PARK; E.S. SEO; R. SINA; S.P. SWORDY; J. WU; J. YANG; Y.S. YOON; R. ZEI; S.Y. ZINNS. P., Wakely; H. S., Ahn; P., Allison; Bagliesi, MARIA GRAZIA; J. J., Beatty; Bigongiari, Gabriele; P., Boyle; T. J., Brandt; J. T., Childers; N. B., Conklin; S., Coutu; M. A., Duvernois; O., Ganel; J. H., Han; J. A., Jeon; K. C., Kim; M. H., Lee; L., Lutz; Maestro, Paolo; A., Malinine; Marrocchesi, PIER SIMONE; S., Minnick; S. I., Mognet; S. W., Nam; S., Nutter; I. H., Park; J. H., Park; N. H., Park; E. S., Seo; R., Sina; S. P., Swordy; J., Wu; J., Yang; Y. S., Yoon; Zei, Riccardo; S. Y., Zin