Indirect searches in the PAMELA and Fermi era

Abstract

The detection of γ -rays, antiprotons and positrons due to pair annihilation of dark matter particles in the Milky Way halo is a viable indirect technique to search for signatures of supersymmetric dark matter where the major challenge is the discrimination of the signal from the background generated by standard production mechanisms. The new PAMELA antiproton data are consistent with the standard secondary production and this allows us to constrain exotic contribution to the spectrum due to neutralino annihilations. In particular, we show that in the framework of minimal supergravity (mSUGRA), in a clumpy halo scenario (with clumpiness factor ⩾10) and for large values of tan ( β ) ⩾ 55 , almost all the parameter space allowed by WMAP is excluded. Instead the PAMELA positron fraction data exhibit an excess that it is very difficult to explain with secondary production. The Fermi-LAT experiment recently reported high precision measurements of the spectrum of cosmicray electrons-plus-positrons (CRE) between 20 GeV and 1 TeV. The spectrum shows no prominent spectral features, and is significantly harder than that inferred from several previous experiments. The PAMELA excess in positron fraction combined with the new Fermi results on the electron+positron spectrum unavoidably testifies the presence of primary positrons in cosmic rays because it is not possible to explain the PAMELA ratio with a deficit of electrons at high energies. Here we discuss the status of indirect dark matter searches and a perspective for PAMELA and Fermi γ -ray space telescope experiments.