Antimatter Annihilation Research Articles

Annihilation of matter and antimatter and the cosmic X-ray background

IN cosmological models where matter and antimatter occur symmetrically in the Universe1–5, their annihilation is likely to take place also at the present time. At the annihilation of a proton and an antiproton, ∼ 1.6 negative electrons and an equal number of positrons, each with an energy of ∼ 10–100 MeV are produced (Fig. 1), together with γ rays and neutrinos6. The initial electron energies can be expected to decrease gradually because of their interaction with cosmic magnetic fields, plasmas, and electromagnetic radiation. As a result of these interactions synchrotron radiation, bremsstrahlung, and inverse Compton radiation are all emitted. When optical photons are scattered against the relativistic electrons, X rays are produced by the inverse Compton effect. This mechanism may be an important source of cosmic X rays. Our purpose here is to study how efficient this X-ray mechanism can be in intergalactic space (where most of the annihilation electrons are expected to be found) and to see whether it can offer an explanation to the cosmic X-ray background observed (see refs 7–9).

Primeval turbulence from matter-antimatter annihilation

In a previous work by two of us, the main difficulties of the theory of galaxy formation from universal primordial cosmic turbulence were focussed; it was mainly found that the decay of the turbulence was so strong during the plasma era that turbulence should have been almost completely washed out before recombination, unless, and only for low-density universes, unlikely large turbulent velocities were postulated at the largest scale of the turbulence at the end of the radiation era. It was suggested that a possibility to turn around such a difficulty should consist in finding en adequate physical energy source feeding the turbulence during at least the whole plasma phase. The present work is intended to test whether matter-antimatter annihilation theory at the origin of the universe, as it is developed by Omnes and his collaborators, may be considered to yield the required energy source of the turbulence. To this aim, the main results of the work of Stecker and Puget concerning the behaviour of the most important quantities of the matter- antimatter annihilation theory are used, in order to describe the properties of the energy source for the turbulence down to recombination time, and extended to take a somewhat more detailed account of theirz and mean matter density dependences. The energy feeding source thus obtained is then introduced into the general framework of the galaxy formation theory from cosmic turbulence taking account of energy dissipation as developed in our previous works. The results obtained concerning the comparison of the main parameters of galaxies derived from the theory with the experimental data are much more satisfactory than in the previous approach, and show that, inside the errors of the present day values, sufficiently good fits are possible in a range of mean universe densities between 0.4 to 1 times the critical density.

Predictions of Extragalactic Gamma Ray Fluxes between 1 and 100 MeV

RECENT theoretical studies have shown the need for observations of isotropic cosmic gamma radiation in the 1–100 MeV energy region. Such observations will enable us to determine the relative importance of the various processes which may produce the observed isotropic X-radiation below 1 MeV and gamma radiation above 100 MeV. The first process to be examined as a possible explanation for the radiation below 1 MeV was Compton interactions between metagalactic cosmic ray electrons and photons of the universal microwave radiation field1–4. Recently, we discussed additional processes which may be important in producing extragalactic gamma radiation. These processes are cosmic ray electron bremsstrahlung with intergalactic matter5, collisions of cosmic ray nuclei with intergalactic matter which result in the production of pi-mesons6,7, and the mutual annihilation of matter and antimatter on possible boundary regions of baryon inhomo-geneity in the universe8. Our purpose here is to discuss some implications of these studies in distinguishing the gamma ray spectra produced by the various processes and placing upper limits on the metagalactic cosmic ray electron and nuclear fluxes. In particular, the results indicate that observational studies of isotropic gamma radiation between 1 and 100 MeV are critical for determining the dominant processes producing gamma rays in the metagalaxy and their cosmological implications.

Antimatter and Tree Rings

RECENTLY, Cowan, et al.1 discussed the interesting case of the Tunguska meteor—the event and its origin mainly in the context of release of a rather high energy of ∼ 1024 ergs on its impact. Various theories concerning its origin and the nature of the energy source were discussed (for example, asteroidal origin and energy from impact or nuclear reactions). They have shown that none of the theories can satisfactorily explain the amount of energy released during the impact. The authors have invoked the antimatter hypothesis and, as an experimental verification to this, have calculated the expected increase in the carbon-14/carbon-12 ratios in the atmosphere subsequent to the fall of the meteorite. Considering the total energy release, they obtained a value of 7 per cent for the expected increase in activity. Their measurements of the atmospheric carbon-14/carbon-12 ratios, based on annual rings of a 300-yr.-old tree, show a possible increase of 1 per cent in the year 1909, leading them to the conclusion that probably l/7th of the energy release in the Tunguska meteorite impact came from antimatter annihilation.