Thursday 28 March 2019
to 16:00 at
Peter von Ballmoos (Institut de Recherche en Astrophysique et Planétologie, Toulouse)
Balloon and satellite experiments detect antimatter in the Universe both directly as a cosmic ray component and indirectly through characteristic annihilation signatures.
Positrons have been studied in cosmic rays for over five decades, just as long as we have been observing them through the 511 keV gamma-rays they emit when annihilating. The question on their origin however is still far from being settled neither for the high-energy cosmic ray positrons nor for the positrons annihilating in the central regions of our Galaxy. Nevertheless the most plausible scenarios for their production all involve processes occurring at the endpoints of stellar evolution.
During forty years, the direct detection of baryonic antimatter has concerned the measurement of antiprotons naturally produced in cosmic ray interactions with the interstellar medium. Recently the tentative detection of a few 3He by AMS has revitalised the discussion on the existence of baryonic antimatter in the Universe. Since revoking an ”MeV bump” hinted in the seventies gamma-ray astronomy has more and more constrained the fraction of antimatter possibly contained in astrophysical objects. The absence of characteristic annihilation features on all scales has virtually ruled out the existence of substantial quantities of antimatter in the observable Universe.
The aim of this talk is to provide a broad overview on the status of direct and indirect detection of antimatter in the Universe.