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

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

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

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

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

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).

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

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?

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

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

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

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

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

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

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/

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)

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

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

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: )

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)