Model-independent implications of the e+, e-, anti-proton cosmic ray spectra on properties of Dark Matter

Abstract

Taking into account spins, we classify all two-body non-relativistic Dark Matter annihilation channels to the allowed polarization states of Standard Model particles, computing the energy spectra of the stable final-state particles relevant for indirect DM detection. We study the DM masses, annihilation channels and cross sections that can reproduce the PAMELA indications of an e+ excess consistently with the PAMELA p-bar data and the ATIC/PPB-BETS e++e- data. From the PAMELA data alone, two solutions emerge: (i) either the DM particles that annihilate into W,Z,h must be heavier than about 10 TeV or (ii) the DM must annihilate only into leptons. Thus in both cases a DM particle compatible with the PAMELA excess seems to have quite unexpected properties. The solution (ii) implies a peak in the e++e- energy spectrum, which, indeed, seems to appear in the ATIC/PPB-BETS data around 700 GeV. If upcoming data from ATIC-4 and GLAST confirm this feature, this would point to a O(1) TeV DM annihilating only into leptons. Otherwise the solution (i) would be favored. We comment on the implications of these results for DM models, direct DM detection and colliders as well as on the possibility of an astrophysical origin of the excess.

Figures (13)

• Figure 1: Three examples of fits of $e^+$ (left), $e^++e^-$ (center), $\bar{p}$ (right) data, for $M=150\,{\rm GeV}$ (upper row, excluded by $\bar{p}$), $M=1\,{\rm TeV}$ (middle row, favored by data), $M=10\,{\rm TeV}$ (lower row, disfavored by the current $e^++e^-$ excess). Galactic DM profiles and propagation models are varied to provide the best fit. See Sec. \ref{['sec:propagation']} for the discussion on the treatment of the uncertain astrophysical background.
• Figure 2: Values of the DM annihilation cross sections suggested by the DM abundance.
• Figure 3: Contour plots of the Sommerfeld enhancement for one abelian massive vector with mass $M_V$ and coupling $\alpha$ to DM (from Sommerfeld2) and the resulting Sommerfeld reduction in the cosmological thermal DM abundance (we here assumed a DM mass $M=1\,{\rm TeV}$).
• Figure 5: Energy spectra of the positron fraction $e^+/(e^-+e^+)$, as produced by DM annihilations into the various possible channels. The DM masses are $\{50,100,\-200,\-500,\-1000,2000,5000,10000,20000\}\,{\rm GeV}$ and can be inferred from the energies at which the spectra drop to zero. In this figure we take a NFW halo, the MED propagation model, boost factor $B_e=1$ and the cross section $\sigma v=3\cdot 10^{-26}\,{\rm cm}^3/{\rm sec}$ naı̈vely suggested by cosmology. For illustration, the upper plots show the expected astrophysical background (upper line) and the data, that can be fitted increasing $B_e\cdot\sigma v$. The dashed curves in the $\mu,\tau,W,Z$ plots represent $\mu_R,\tau_R, W_L,Z_L$ polarizations, while the continuous lines represent $\mu_L,\tau_L,W_T,Z_T$ polarizations.
• Figure 6: The same as in Fig. \ref{['fig:espectra']} for the energy spectrum of the $\bar{p}/p$ ratio.