Antimatter research in space

Journal of Physics: Conference Series, 2008

Two of the most compelling issues facing astrophysics and cosmology today are to understand the nature of the dark matter that pervades the universe and to understand the apparent absence of cosmological antimatter. For both issues, sensitive measurements of cosmicray antiprotons and positrons, in a wide energy range, are crucial.

Il Nuovo Cimento A, 1986

Nuclear Physics B - Proceedings Supplements, 1999

After a brief discussion of the theoretical specukions concerning the presence of cosmological antimatter, the status of the experimental investigations is revised. The observational programs for the next future (BESS, ISOMAX, WIZARD, WIZARD/PAMELA and AMS) are illustrated, and possible further developments discussed.

Physical Review Letters, 1996

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 antiproton͞proton 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 ϳ10 7 yr. PACS numbers: 98.70.Sa, 14.20.Dh, 95.85.Ry Measurement of the antiproton abundance in the cosmic radiation bears strongly on questions ranging from the possibility of a baryon symmetric universe to characterizing the origin and transport of the cosmic rays. However, the interpretation of cosmic ray antiproton measurements has been very uncertain ever since their discovery by Golden et al. . While antiprotons in the cosmic radiation are expected as "secondary" products of interactions of the primary cosmic radiation, principally protons, with the ambient interstellar medium (ISM) [2-4], the first positive measurements [1,5,6] reported higher antiproton fluxes than predicted by contemporary models of cosmic ray transport. Of the numerous explanations proposed (reviewed in Stephens and Golden [7]), one class assumed that secondary antiprotons are produced by cosmic ray protons and helium which have passed through more matter than implied by measured secondary͞primary ratios of heavier elements (e.g., boron͞carbon). Others considered "exotic" sources such as the evaporation of primordial black holes, the decay of dark matter, or acceleration in relativistic plasmas. It was also suggested that the excess could be a manifestation of a baryon symmetric cosmology . The largest discrepancy was at ϳ200 MeV [6], where antiproton production in p-p interactions is heavily suppressed ; however, later measurements gave corresponding upper limits which were significantly lower . The Isotope Matter-Antimatter Experiment (IMAX) and other recent experiments [13] were designed to clarify these issues.

The Astrophysical Journal, 1996

The antiproton-to-proton ratio, p/p, in cosmic rays has been measured in the energy range 3.7-19 GeV. This measurement was carried out using a balloon-borne superconducting magnetic spectrometer along with a gas Cerenkov counter, an imaging calorimeter, and a time-of-flight scintillator system. The measured p/p ratio was determined to be 1.24 Ϫ0.51 ϩ0.68 ϫ 10 Ϫ4 . The present result, along with other recent observations, shows that the observed abundances of antiprotons are consistent with models in which antiprotons are produced as secondaries during the propagation of cosmic rays in the Galaxy.

Proceedings of International Europhysics Conference on High Energy Physics — PoS(hep2001)

The whole set of astrophysical data indicates that our Universe is globally baryon asymmetrical. Nevertheless a possibility of existence of relatively small amount of sufficiently large antimatter regions is not excluded. Such regions can survive the annihilation with surrounding matter only in the case if their sizes exceed a certain scale. It is shown that quantum fluctuations of a complex scalar field caused by inflation can generate large antimatter domains progenitors, which contribute insignificantly to the total volume of the Universe. The resulting distribution and evolution of such antimatter regions could cause every galaxy to be a harbour of an anti-star globular cluster. The existence of one of such anti-star globular cluster in our Galaxy, does not contradict the observed γ-ray background, but the expected fluxes of 4 He and 3 He from such an antimatter object can be searched for in PAMELA experiment and are definitely accessible for the sensitivity of coming AMS02 experiment.

The Astrophysical Journal, 2000

We report new results for the cosmic-ray antiproton-to-proton ratio from 3 to 50 GeV at the top of the atmosphere. These results represent the first measurements, on an event-by-event basis, of mass-resolved antiprotons above 18 GeV. The results were obtained with the NMSU-WIZARD/CAPRICE98 balloon-borne magnet spectrometer equipped with a gas-RICH (Ring-Imaging Cerenkov) counter and a silicon-tungsten imaging calorimeter. The RICH detector was the first ever flown that is capable of identifying charge-one particles at energies above 5 GeV. The spectrometer was flown on 1998 May 28-29 from Fort Sumner, New Mexico. The measured /p p ratio is in agreement with a pure secondary interstellar production.

Hyperfine Interactions, 2012

The PAMELA satellite-borne experiment has presented new results on cosmic-ray antiparticles that can be interpreted in terms of DM annihilation or pulsar contribution. The instrument was launched from the Baikonur cosmodrome and it has been collecting data since July 2006. The combination of a permanent magnet silicon strip spectrometer and a silicon-tungsten imaging calorimeter allows precision studies of the charged cosmic radiation to be conducted over a wide energy range with high statistics. The primary scientific goal is the measurement of the antiproton and positron energy spectrum in order to search for exotic sources. PAMELA is also searching for primordial antinuclei (anti-helium), and testing cosmic-ray propagation models through precise measurements of the antiparticle energy spectrum and precision studies of light nuclei and their isotopes. This talk illustrates the most recent scientific results obtained by the PAMELA experiment.

Particles, Strings and Cosmology (Pascos 99) - Proceedings of the 7th International Symposium, 2000

Cosmic ray antiprotons have been detected for over 20 years and are now measured reliably. Standard particle and astrophysics predict a conventional spectrum and abundance of secondary antiprotons consistent with all current measurements. These measurements place limits on exotic Galactic antiproton sources and nonstandard antiproton properties. Complications arise, particularly at low energies, with heliospheric modulation of cosmic ray fluxes and production of standard secondaries from A > 1 nuclear targets. Future experiments and theoretical developments are discussed.

2010