1 / 20

Results from Cosmic-Ray Experiments

Vasiliki Pavlidou Kavli Institute for Cosmological Physics, The University of Chicago. Results from Cosmic-Ray Experiments. Outline. Ultra-high--energy cosmic-rays: issues and detection techniques A hybrid experiment: the Pierre Auger Observatory

devaki
Download Presentation

Results from Cosmic-Ray Experiments

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Vasiliki Pavlidou Kavli Institute for Cosmological Physics, The University of Chicago Results from Cosmic-Ray Experiments

  2. 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. UHECRs: the questions • Highest energy particles (> 1018 eV) • Spectrum? • Protons, heavier nuclei, photons? • Top-down or bottom-up? • Local or cosmological? • Sources? S. Swordy

  4. Detecting UHECRs • Detection techniques: • detect fluorescent emittion generated by shower (Fly’s Eye, HiRes: Sokolsky Panofsky Prize talk, session E2) • detect shower footprint on ground(AGASA) Credit: Cosmus team (http://astro.uchicago.edu/cosmus)

  5. 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, 3,000km2

  6. 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. Recent CR results and implications for neutrinos and astrophysics

  8. 2.81 5.1 2.69 4.2 I. The CR spectrum at the highest energies • CR flux above 1019.6 eV suppressed! (HiRes, Auger) • But what does this mean?

  9. E. Armengaudsims by A. Kravtsov 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

  10. AGN Cen A II. The UHECR Sky is anisotropic Pierre Auger Collaboration 2007, Science, 318, 939Pierre Auger Collaboration 2008, APh, 29, 188 Patrick Younk talk - session T8, Monday @ 3:30

  11. 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. 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 individualsources • Calculate fluxes, spectra • Answer fundamentalquestions about nature’smost powerful accelerators, their physics, and their energy sources • Map the Galactic/intergalactic magnetic field! B. Siffert

  13. n  p + e- + e ++ +   + e+ + e +  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 + + GZK, Photopion, or Cosmogenic Neutrinos

  14. 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. 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/9809144

  16. 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 Lint () ~ 500 km (for >95 degrees: Earth opaque)‏ LEloss (~ 10 km (for e: much smaller) Ldecay () ~ 50 km (for : much larger)

  17. Down-going neutrinos Old hadronic shower Young neutrino shower

  18. Earth-skimming neutrinos

  19. Auger (and HiRes) neutrino limits Pierre Auger Collaboration 2008, PRL submitted, arXiv:0712.1909(HiRes limits from: K. Martens for the HiRes Collaboration 2007, arXiv: 0707.4417)

  20. 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)

More Related