Abstract
We have witnessed in the past decade the observation of a puzzling cosmic-ray excess at energies larger than $10$ GeV. The AMS-02 data published this year has new ingredients such as the bump around $300$ GeV followed by a drop at $800$ GeV, as well as smaller error bars. Adopting the background used by the AMS-02 collaboration in their analysis, one can conclude that previous explanations to the new AMS-02 such as one component annihilating and decaying dark matter as well as pulsars seem to fail at reproducing the data. Here, we show that in the right-handed neutrino portal might reside the answer. We discuss a decaying two-component dark matter scenario where the two-body decay products are right-handed neutrinos that have their decay pattern governed by the type I seesaw mechanism. This setup provides a very good fit to data, for example, for a conservative approach including just statistical uncertainties leads to $\chi^2/d.o.f \sim 2.3$ for $m_{DM_1}=2150$ GeV with $\tau_{1}=3.78 \times 10^{26}$ s and $m_{DM_2}=300$ with $\tau_{2}=5.0 \times 10^{27}$ s for $M_N=10$ GeV, and, in an optimistic case, including systematic uncertainties, we find $\chi^2/d.o.f \sim 1.12$, for $M_N = 10$ GeV, with $m_{DM_1}=2200$ GeV with $\tau_{1}=3.8 \times 10^{26}$ s and $m_{DM_2}=323$ GeV with $\tau_{2}=1.68 \times 10^{27}$ s.
Highlights
The observation of cosmic rays has boosted our understanding of astrophysical phenomena that undergo diffusion and energy loss processes in the intergalactic medium
Including only the statistical uncertainties, we find the best fit of χ2=DOF ∼ 2.3 for mDM1 1⁄4 300 with τ1 1⁄41.67×1027 s and mDM2 1⁄4 2000 GeV with τDM2 1⁄4 4 × 1026 s for MN 1⁄410GeV, and, for the optimistic case, including systematic uncertainties, we get τ1 1⁄4 1.68× 1027 s and τDM2 1⁄43.8×1026 s, for mDM1 1⁄4 323 GeV and mDM2 1⁄4 2200 GeV, respectively, with MN 1⁄4 10 GeV, yielding χ2=DOF ∼ 1.12
The scenario involves two dark matter (DM) particles decaying into two right-handed neutrino (RHN) pairs
Summary
The observation of cosmic rays has boosted our understanding of astrophysical phenomena that undergo diffusion and energy loss processes in the intergalactic medium. In 2008 the payload for antimatter matter exploration and light-nuclei astrophysics (PAMELA) surprisingly announced the first evidence of a rise in the cosmic-ray positron fraction at GeV energies with high statistics [1]. Taking advantage of the absent onboard magnet, they could distinguish electrons from positrons by exploiting Earth’s shadow, which is offset in opposite directions for opposite charges due to Earth’s magnetic field. With this technique, they were able to observe a positron fraction rise for energies between 20 and 200 GeV [2]. The AMS mission measured the positron fraction up to 350 GeV [3] and reported a flat positron fraction for energies above 150 GeV
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