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The National Science FoundationThe Kavli Foundation APS April 2008 Meeting - St. Louis, Missouri Results from Cosmic-Ray Experiments Vasiliki Pavlidou.

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Presentation on theme: "The National Science FoundationThe Kavli Foundation APS April 2008 Meeting - St. Louis, Missouri Results from Cosmic-Ray Experiments Vasiliki Pavlidou."— Presentation transcript:

1 The National Science FoundationThe Kavli Foundation APS April 2008 Meeting - St. Louis, Missouri Results from Cosmic-Ray Experiments Vasiliki Pavlidou Kavli Institute for Cosmological Physics, The University of Chicago

2 The National Science FoundationThe Kavli Foundation APS April 2008 Meeting - St. Louis, Missouri Outline Ultra-high--energy cosmic-rays: issues and detection techniques A hybrid experiment: the Pierre Auger Observatory Recent results from cosmic ray experiments: GZK flux suppression; anisotropies at the highest energies Sources of UHE neutrinos and expected fluxes Neutrino detection techniques for UHE Cosmic-Ray Experiments Current neutrino limits from Auger and HiRes Outlook

3 The National Science FoundationThe Kavli Foundation APS April 2008 Meeting - St. Louis, Missouri UHECRs: the questions Highest energy particles (> eV) –Spectrum? – Protons, heavier nuclei, photons? – Top-down or bottom-up? – Local or cosmological? – Sources? S. Swordy

4 The National Science FoundationThe Kavli Foundation APS April 2008 Meeting - St. Louis, Missouri Detecting UHECRs Credit: Cosmus team (http://astro.uchicago.edu/cosmus ) Detection techniques: detect fluorescent emittion generated by shower (Fly’s Eye, HiRes: Sokolsky Panofsky Prize talk, session E2) detect shower footprint on ground (AGASA)

5 The National Science FoundationThe Kavli Foundation APS April 2008 Meeting - St. Louis, Missouri The Pierre Auger Observatory of Ultra-high Energy Cosmic Rays: a hybrid experiment ~400 scientists from ~70 Institutions and 17 countries Currently: 1550 tanks taking data 24 fluorescence telescopes in 4 stations overlooking array AIM: 1600 tanks, 3,000km 2

6 The National Science FoundationThe Kavli Foundation APS April 2008 Meeting - St. Louis, Missouri Advantages of the hybrid technique Good statistics (100% duty cycle for SD) Straight-forward aperture and exposure determination for SD Model-independent energy calibration for FD  calibration of SD using hybrid events Accurate geometry reconstruction for hybrid events (arrival direction determination <0.2 degrees)  calibration of SD (arrival direction accuracy typically < 1 degree).

7 The National Science FoundationThe Kavli Foundation APS April 2008 Meeting - St. Louis, Missouri Recent CR results and implications for neutrinos and astrophysics

8 The National Science FoundationThe Kavli Foundation APS April 2008 Meeting - St. Louis, Missouri I. The CR spectrum at the highest energies CR flux above eV suppressed! (HiRes, Auger) But what does this mean?

9 The National Science FoundationThe Kavli Foundation APS April 2008 Meeting - St. Louis, Missouri Interpretation of CR flux suppression Possible interpretations: – cosmological suppression due to energy losses on CMB (GZK cutoff) –accelerators running out of steam (cutoff in source spectrum) How to tell: –Measure spectra of individual nearby sources (difficult!) –if suppression cosmological: highest energy (super-GZK) events only sample local universe (highly anisotropic)  sky distribution of super-GZK events might look anisotropic E. Armengaud sims by A. Kravtsov

10 The National Science FoundationThe Kavli Foundation APS April 2008 Meeting - St. Louis, Missouri II. The UHECR Sky is anisotropic Cen A AGN Patrick Younk talk - session T8, 3:30 Pierre Auger Collaboration 2007, Science, 318, 939 Pierre Auger Collaboration 2008, APh, 29, 188

11 The National Science FoundationThe Kavli Foundation APS April 2008 Meeting - St. Louis, Missouri Implications for Charged Particle Astrophysics Flux suppression at highest energies is cosmological Sources are extragalactic, and extend to cosmological distances The highest-energy cosmic-ray sky is anisotropic, but nature of sources is still unclear Intergalactic B-field small  cosmic rays good messengers for mapping the nearby universe Astrophysics! –UHECR source identification, study –Timely concurrent operation with gamma-ray, neutrino, and low- energy photon observatories –UHECR astronomy possible: time to build a bigger telescope!  Auger North

12 The National Science FoundationThe Kavli Foundation APS April 2008 Meeting - St. Louis, Missouri Auger North Planned location in Colorado, US Full-sky coverage Optimized for operation in energies where arrival directions are anisotropic Sufficient exposure (~ 7 x South) to: –Detect individual sources –Calculate fluxes, spectra –Answer fundamental questions about nature’s most powerful accelerators, their physics, and their energy sources –Map the Galactic/intergalactic magnetic field! B. Siffert

13 The National Science FoundationThe Kavli Foundation APS April 2008 Meeting - St. Louis, Missouri Implications for Neutrino Astrophysics GZK cutoff observed  cosmogenic neutrinos guaranteed! High Energy Proton sees Cosmic Microwave Background as High Energy Gamma Rays! p+  cmb   +  p +  0  n +  + n  p + e - + e   +   + +    +  e + + e +   GZK, Photopion, or Cosmogenic Neutrinos

14 The National Science FoundationThe Kavli Foundation APS April 2008 Meeting - St. Louis, Missouri GZK neutrinos guaranteed but… … flux and spectrum are model dependent conversely: if we measure cosmogenic neutrino flux, we can constrain source models Allard et al ‘06

15 The National Science FoundationThe Kavli Foundation APS April 2008 Meeting - St. Louis, Missouri Other potential sources of UHE neutrinos Astrophysical: Interactions of accelerated hadrons within possible sources (GRBs, AGN) Exotic: Topological defects, superheavy dark matter L. Cazon fluxes from Protheroe 1999 review, arXiv:astro-ph/

16 The National Science FoundationThe Kavli Foundation APS April 2008 Meeting - St. Louis, Missouri Neutrino detection in cosmic ray air shower experiments Two Detection Channels: –Down-going neutrinos (all flavors) interacting in the atmosphere –Up-going tau neutrinos interacting in Earth crust -> Earth skimming neutrinos L int ( ) ~ 500 km (for  >95 degrees: Earth opaque)‏ L Eloss (  ~ 10 km (for e: much smaller) L decay (  ) ~ 50 km (for  : much larger)

17 The National Science FoundationThe Kavli Foundation APS April 2008 Meeting - St. Louis, Missouri Down-going neutrinos Young neutrino shower Old hadronic shower

18 The National Science FoundationThe Kavli Foundation APS April 2008 Meeting - St. Louis, Missouri Earth-skimming neutrinos

19 The National Science FoundationThe Kavli Foundation APS April 2008 Meeting - St. Louis, Missouri Auger (and HiRes) neutrino limits Pierre Auger Collaboration 2008, PRL submitted, arXiv: (HiRes limits from: K. Martens for the HiRes Collaboration 2007, arXiv: )

20 The National Science FoundationThe Kavli Foundation APS April 2008 Meeting - St. Louis, Missouri Outlook UHE CR results: flux suppression, anisotropies at highest energies Charged particle astronomy possible; with increased statistics: source identification, measurement of flux, spectra GZK cutoff observed: CR sources extragalactic, cosmological Implications for neutrino astrophysics: cosmogenic neutrino flux guaranteed, flux associated with UHECR sources plausible UHECR experiments capable of discriminating neutrino-like events Current limits at ~10x GZK flux Detection of cosmogenic neutrinos, neutrinos from UHECR sources in <10yr in most optimistic models (meaningful constraints guaranteed within same time)


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