Fermi/LAT observations of Dwarf Galaxies highly constrain a Dark Matter interpretation of Excess Positrons seen in AMS-02, HEAT, and PAMELA DPF 2015 – UNIVERSITY OF MICHIGAN, ANN ARBOR. ALEJANDRO LOPEZ IN COLLABORATION WITH: C. SAVAGE, D. SPOLYAR AND D. ADAMS

Outline:  Brief Introduction  Goal  Technique  Results  Conclusion  Future Work

Indirect Detection χ χ SM Fermi/LAT HESS AMS PAMELA ICECUBE Super-Kamiokande

Fermi/LAT AMS-02 M. Ackermann et al. [Fermi-LAT Collaboration], Phys. Rev. D 89 M. Boudaud et al., arXiv: [astro-ph.HE]

Fermi/LAT AMS-02 M. Ackermann et al. [Fermi-LAT Collaboration], Phys. Rev. D 89 M. Boudaud et al., arXiv: [astro-ph.HE]

Best Fit Dark Matter models for explaining AMS-02 Positron Excess Boudad et al. (arXiv: ) three distinct dark matter annihilation channels:  Single Channel: { b¯b,e+e−,µ+µ−,τ+τ−} MED  4 lepton case: DM + DM -> φ+φ -> 4 l¯l Best Fit propagation model  Mixed Channel: b¯b + l¯l with and without having lepton BR equal. MED Propagation Model Best Fit propagation model marginalized over 1623 combinations of the transport parameters {δ, K0, L, Vc, VA}.

Goal To establish if the null results from the Fermi/LAT experiment measuring gamma-rays originating in Dwarf Galaxies (2014 data) are in tension with a dark matter interpretation for the AMS- 02 positron excess.

Technique Extend Combined Likelihood Analysis done by Fermi/LAT utilizing gamma-ray data from 15 non-overlapping dwarf galaxies to dark matter masses greater than 10 TeV in order to establish the viability for a dark matter interpretation of the AMS-02 positron excess.

Results I Showing Fermi/LAT bounds (blue) and AMS-02 best fit 2- σ regions. Red contour is assuming MED propagation model, and grey region marginalizes over 1623 propagation parameters.

Results II - Showing Fermi/LAT bounds, along with AMS-02 best fit region for single and mixed channels. Mixed channels assume MED propagation model. - 2e and 2 μ are not excluded by Fermi/LAT, but give a bad fit to AMS-02 data.

Results III -Showing Fermi/LAT bounds, along with AMS-02 best fit region for 4-leptons channel. Mixed channels assume MED propagation model. Only showing 4τ Fermi/LAT bounds, we postpone calculation of 4µ and 4e due to complication with Final State Radiation for future paper. 4e gives bad fit to AMS-02 Positron excess, thus potentially Only 4µ survives. -Mixed 4-lepton channel Survives for masses > 40 TeV

Planck 2015 Results Planck 2015 Results: arXiv A)We put our results on arxiv one month earlier Our work: arXiv Planck: arXiv B) Planck bounds are for much smaller range of WIMP masses Our work: m χ =[0.350 – 30] TeV Planck: m χ =[1 - 3] TeV

Conclusion:  For the single channel case, we find that dark matter annihilation into {b¯b,e+e−,µ+µ−,τ+τ−,4-e, or 4-τ} is ruled out as an explanation of the AMS positron excess (here b quarks are a proxy for all quarks, gauge and Higgs bosons).  In addition, we find that the Fermi/LAT 2σ upper limits, assuming the best-fit AMS-02 branching ratios, exclude multichannel combinations into b¯ b and leptons.  Of all the channels we considered, the only viable channel that survives the Fermi/LAT constraint and produces a good fit to the AMS- 02 data is annihilation (via a mediator) to 4-µ, or mainly to 4-µ in the case of multichannel combinations.  The tension between the results might relax if the branching ratios are allowed to deviate from their best-fit values, though a substantial change would be required; the positron excess comes partly from point sources; or there is a local dark matter overdensity.