Neutrinos - KICP Workshops & Events | KICP Workshops · Geminga was much stronger in the past and...
Transcript of Neutrinos - KICP Workshops & Events | KICP Workshops · Geminga was much stronger in the past and...
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Neutrinos:Candidates and Probes of Dark Matter
Hasan YükselBartol Research Institute
Univ. of Delaware
KICP WorkshopThe impact of high-energy
astrophysics experimentson cosmological physics
27-28 October, 2008
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Dark Matter: The Beginnings1930s: Zwicky proposed Dark
Matter to explain the mass to light ratio of Coma galaxy cluster
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Model Independent Limit on DM Annihilation Cross Section
• Assume DM annihilations only produce Standard Model final states
• Stringent upper limit on total annihilation cross section can be obtained by assuming only neutrinos are produced in final states (worst case, least visible)
• Anything else will eventually produce much more visible gamma rays (leading to a stronger limit)
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Compare to Atmospheric Nu Flux
Yuksel, Horiuchi, Beacom, Ando 2007Beacom, Bell, Mack 2006
“Even Neutrinos are overproduced”
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Constraints on sterile neutrino DM
Yuksel, Beacom, Watson 2008
Watson Beacom Yuksel Walker 2006
Abazajian, Fuller 2002Kishimoto, Fuller 2008
Teegarden, Watanabe2006
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DM and Multi-GeV Positron Excess
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TeV Gamma Rays From Geminga and Multi-GeV Positron Excess
Hasan YükselBartol Research Institute&University of Delaware
KICP WorkshopThe impact of high-energy
astrophysics experimentson cosmological physics
27-28 October, 2008
(in collab. with Matt Kistler and Todor Stanev)
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Geminga:
• Radio quite
• First pulsar to be discovered through gamma rays
• Until recently, no evidence of a high energy activity beyond immediate neighborhood
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Milagro Galactic Plane Survey
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Immediate Implications:
• Milagro detection puts Geminga among growing class of TeV PWNe
• Detection of TeV gamma rays indicates theexistence of a nearby cosmic ray accelerator:– If gamma rays have a leptonic origin, the
source is young & close enough to make a plausible contribution to CR positrons
– Alternatively, a neutrino signal would be expected from a hadronic source
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More Distant PWN by HESSHESS J1825-137, Aharonian et al.
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TeV Gamma Rays from Geminga
Yuksel, Kistler, Stanev 2008
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Galactic Plane by EGRET
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Fermi (GLAST) / Veritas Prospects
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Positron Injection to ISM & Diffusion
Atoyan, Aharonian, Volk, 1995
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Local Positrons from a Nearby Continuously Emitting Source
Assuming breaking via magnetic dipole radiation:Pulsar spin down luminosity evolves as
The injection rate of relativistic e-e+ by Geminga:
Geminga was much stronger in the past and dominated the TeV sky: Multi-GeV positrons may still be reaching us today
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Background Cosmic Ray Fluxes& Plausible Geminga Contributions
Yuksel, Kistler, Stanev 2008
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Accounting for Positron Excess?
PAMELA should yield an improved picture of the positron fraction
Yuksel, Kistler, Stanev 2008
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Hadronic Alternative: TeV Neutrinos• If a nucleonic wind carry away much of the spin
down energy of pulsar, gamma rays may be produced via decay of neutral pions from hadronic scattering
• >1 Neutrino-induced muon in IceCube
Beacom, Kistler 2007
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Amanda-II Hot(test) Spot
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Conclusions
• More data should become available soon:– GeV Gamma Rays: Fermi (GLAST)
– TeV Gamma Rays: Veritas, Future ACTs
– Multi-GeV Positrons: PAMELA, AMS?
– TeV Neutrinos: IceCube
• Which may result in: – Developing more detailed models, including
time & spatial evolution in the source
– Unraveling Multi-GeV positron excess?
– Discovering First TeV neutrinos source?