Imaging Galactic Dark Matter with IceCube’s High-Energy Cosmic Neutrinos Ali Kheirandish The 26th International Workshop on Weak Interactions and Neutrinos (WIN2017) University of California-Irvine, June, 19, 2017
Based on [arXiv:1703.00451] C. A. Argüelles, A.K, A. C. Vincent Imaging Galactic Dark Matter with High-Energy Cosmic Neutrinos Also 𝜉 FATE : Neutrino Fast Attenuation Through Earth, coming soon! 2
IceCube & Cosmic Neutrinos IceCube Neutrino Observatory discovered neutrinos with extraterrestrial origin in 2013 in a • search for High Energy Starting Event (HESE). Observation of a clear excess —>6 sigma— of HE neutrino flux above the atmospheric • background. Observation of astrophysical flux was confirmed in through going tracks analysis. • 3
Astrophysical Neutrino Observables Arrival direction Neutrino energy Flavour ( e, µ, τ ) Deposited Topology EM-equivalent muon shower track Aaron Vincent 4
4 Years of HESE [IceCube 2015] 53 Events in 4 years. - Events arrival directions is compatible with isotropic hypothesis . - No correlation with Galactic plane . - Event distribution suggests extragalactic origin for the majority of the events. - Flavor ratio is consistent with 1:1:1 ratio . - 5
Cosmic Neutrinos: Internal Complementarity HE cosmic neutrino flux: new opportunities for new physics • studies. A high degree of complementarity exist between astrophysical • and cosmological observations. [Yvonne Wong] What can we understand from DM-neutrinos interaction? • 6
Dark matter-neutrino interaction? - What is dark matter? - What SM particles does dark matter DM ? SM interact with? - How does it interact? ) ( ) ( ∃ ∃ implies ? ? annihilation scattering = direct detection if = quarks, then ? (LUX, LZ, SuperCDMS, …) But if too light, or does not talk to quarks, then ? could be neutrinos Aaron Vincent 7
DM-Neutrino Interaction in Literature 8
DM-Neutrino Interaction Low-Energy Limit & Cosmology Generic scattering cross section for E ν ⌧ m χ Perturbation damping limits 1) σ → const. 2) σ → const. × E 2 ν × ( T ν /T t oday ) 2 [Escudero et.al, 2016] 9
DM-Neutrino Interaction At High-Energy? σ DM − ν ∝ E 2 ν IceCube has seen events above a PeV…. ◆ 2 ✓ PeV ∼ 10 30 T ν ,recomb. Let’s look there! 10
DM density is largest in center of the galaxy. ν ν ν ν ν DM- 𝜉 interaction will result in scattering of neutrinos from extragalactic sources, leading to ν anisotropy and energy loss . ν
In Practice Z column density: τ ( b, l ) = n χ ( x ; b, l ) dx. l.o.s b, l : galactic latitude, longitude Z ∞ E d σ ( ˜ d Φ ( E, τ ) E, E ) d ˜ Φ ( ˜ = − σ ( E ) Φ ( E, τ ) + E, τ ) d τ dE E scattering from E scattering to E from to any energy any energy Ẽ solve to find flux at Earth at energy E and direction (b,l) 12
Two fiducial simplified models χ χ g χ Fermion DM , vector mediator : similar to a leptophillic Z’ model φ Scales strongly with E g ν ν ν ν ν φ g g Scalar DM , fermionic mediator : χ χ e.g. sneutrino dark matter, neutralino g ν ν mediator. Resonant behaviour (s-channel) φ χ χ g 13
Dark matter column density* seen from Earth Simulation including e ff ects of detector, Earth * Einasto 14
Energy & morphology Energy Direction Resonance @ 810 TeV IceCube HESE events 15
Likelihood Test We test the likelihood of events originating from 3 components: • Astrophysical neutrino component modified by DM-neutrino interaction, -2 spectrum originating from E • Atmospheric neutrinos • Atmospheric muons We establish a limit based on MCMC scan of the parameter space of each interaction model. Parameters: � � m χ , m φ , g, N astro , N atmo , N µ 16
Constraints 1 1 0.5 0.5 0 0 -0.5 -0.5 -1 -1 -1.5 -1.5 -2 -2 -2.5 -2.5 Scalar DM Fermionic DM Fermionic Mediator Vector Mediator With only 53 events, can do better than cosmology in some ranges. 17
Summary & Outlook • No reason to believe DM-neutrino interactions aren’t there. • Isotropy of the signal can be used to constrain such interactions. • Can even do better than cosmology in some ranges, mainly 1-100 MeV. • Need more statistics: forecasts for IceCube-Gen2 & more studies to come. 18
APPENDIX
DM-neutrino interactions: two constraints from cosmology Perturbation Extra radiation N eff damping If DM is light (< 10 MeV) it can dump Scattering damps entropy into neutrino sector as it power spectrum of becomes non-relativistic primordial fluctuations BBN CMB neutrons less Shifted peaks from boltzmann different sound suppressed at FO: propagation length more D, He Boehm et. al 1404.7012 Upper limit on upper limit on DM mass cross section Aaron Vincent
DM-neutrino interactions: cosmology (I) Early universe: lots of dark matter, lots of neutrinos Thermal: if m ~ T v ,decoupling , then DM dumps energy into neutrino H 2 = 8 π sector as it becomes nonrelativistic. This means that there is more 3 ρ energy density in the neutrino sector, accelerating the expansion of the Universe Faster expansion: 1) During BBN: neutrons less boltzmann-suppressed at freeze-out: can form more Deuterium, helium 2) During recombination: acoustic peaks are shifted since sound propagation changed R. Wilkinson, ACV, C. Boehm, C. McCabe 1602.01114 m χ & 5 − 10MeV 21 Aaron Vincent
DM-neutrino interactions: cosmology (II) Power “bled away” on small scales by neutrinos streaming away; increased correlations on large scales CMB Wilkinson et al. 1401.7597 Escudero … ACV 1505.06735 matter Boehm et. al 1404.7012 22 Aaron Vincent
Backgrounds Neutrinos from atmospheric IceCube ICRC 1510.05223 showers can fail to trigger the vetos. These are mostly upgoing (from the north), but concentrated around the horizon. HESE: ~ 12/53 atmospheric neutrinos Muons from atmospheric showers can slip through the veto region. These occur at low energies, and only from the southern (downgoing) direction HESE: ~ 10/53 atmospheric muons 23
Distribution of flux components 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 0 10 20 30 40 50 60 70 80 24
DM profiles 10 2 Isothermal NFW Einasto 10 1 ρ DM [ GeV cm - 3 ] NFW c 10 0 ρ ⊙ = 0.4 GeV cm - 3 10 - 1 10 - 2 r ⊙ = 8.5 kpc 10 - 3 0.1 1 10 100 r [ kpc ] arXiv:1503.07169
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