Cosmic positron and electron excesses: is the dark matter solution a good bet? par Julien Lavalle (Turin)

Thursday 5 Feb 2009, 11:00 → 12:00 Europe/Paris

salle 9 (LPSC)

The PAMELA collaboration has recently released its measurements of the cosmic ray positron fraction over an unprecedented energy range, seemingly indicating an excess between 10 GeV to 270 GeV with respect to the current predictions of the secondary positron background. In the same time ATIC has unveiled a less prominent feature in the cosmic electron spectrum, but at higher energy. It is well known for a long time that standard astrophysical sources, like pulsars and supernova remnants could explain both these features, but there could also be contributions from dark matter (DM) annihilation. We will discuss this issue in the light of our recent (and ongoing) theoretical works on positrons, both on the secondary background and on primary signatures (standard as well as exotic). We will emphasize the impact of the theoretical uncertainties affecting the propagation modelling. More specifically on the DM hypothesis, we will discuss the potential role of cosmological subhalos in the Galaxy (so-called DM clumps), showing that they are unlikely to significantly boost the cosmic rays induced by conventional DM annihilation, even in optimistic scenarios. We will finally comment on the constraints obtained from other astrophysical messengers, like antiprotons and gamma-rays, underlying the would-be hints of DM manifestations.

Slides lavalle_05022009.pdf.pdf