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Astrophysical Neutrinos: A Thorny Problem

Astrophysical Neutrinos: A Thorny Problem. Astrophysical Hadron Accelerators The Neutrino Connection Ideal km 3 Detection Summary of Experimental Limits Conclusions. Neutrino Astronomy: The Concept. Stable particles: p, g, n Accelerator: magnetic shocks and relativistic blast waves.

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Astrophysical Neutrinos: A Thorny Problem

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  1. Jodi Lamoureux, LBNL/NERSC June 2002

  2. Astrophysical Neutrinos: A Thorny Problem • Astrophysical Hadron Accelerators • The Neutrino Connection • Ideal km3 Detection • Summary of Experimental Limits • Conclusions Jodi Lamoureux, LBNL/NERSC June 2002

  3. Neutrino Astronomy: The Concept • Stable particles: p, g, n • Accelerator: magnetic shocks and relativistic blast waves. • Targets are traditional HEP • Astrophysical Sources: • GRB, AGN, Galaxy/Sag-A, SN • GZK ( p + CMB g) • Topological defects • Cosmic Rays: • Atmospheric Muons • Atmospheric Neutrinos Jodi Lamoureux, LBNL/NERSC June 2002

  4. CR and Photon Spectra TeV g absorbed Kpc GeV g-rays Radio CMB Visible • CR spectrum is nearly E-2 dN/dE • Fermi acceleration is the best theory for high energy CR spectrum. • Below knee – galactic protons • Above knee – galactic ions • Above ankle – extragalactic protons? • Above GZK - ??? Waxmann & Bachall hep-ph/0206217 • Photon spectrum • Not Generally a power-law: Blackbody, Synchrotron, Compton • CR contribution: p + g p0 + X  g + g • Universe Opaque to TeV g 1st Confirmation from SN remnants. 1 particle per m2-second Cosmic Ray Flux (m2 sr s GeV) -1 Knee 1 particle per m2-year Ankle 1 particle per km2-year GeV TeV PeV EeV Jodi Lamoureux, LBNL/NERSC June 2002

  5. Hadronic Photons in the News Enomoto, et al. Nature 416, April 2002 • Cangaroo reported in May: • TeV power-law spectrum of photons from overlap region of two SN ~6 kpc distance ~3-10 mG ~ 100 p/cm3 ambient density • Fermi accelerated protons: p + p  p0 + X  g + g • Ruled out • Synchrotron emission (solid) • inverse compton emission (dot) • Bremsstrahlung (dash) • June 25 preprint: ”No evidence yet for hadronic TeV g emision…” Reimer & Pohl Astro-ph/0205256 v3. Jodi Lamoureux, LBNL/NERSC June 2002

  6. CR Acceleration Candidates • Most candidates assume elastic “collisionless” acceleration. Lamar Radius ~ E/ZB • Pulsars • Active Galaxies • Radio Galaxy Lobes • GRB – relativistic expanding fireball Jodi Lamoureux, LBNL/NERSC June 2002

  7. Proton Acceleration Sites Jets from AGN M87 in Virgo Jodi Lamoureux, LBNL/NERSC June 2002

  8. Accretion Disks Pulsar in Crab Pulsar Vela Active Galaxy NGC 4261 Jodi Lamoureux, LBNL/NERSC June 2002

  9. Crab Movie Courtesy of J.Hester, K.Mori, D.Burrows, P.Scowen, M.Haverson, C. Michel, J.Gallagher, J.Graham 2001 HST and Chandra Monitoring of the Crab Synchrotron Nebula, Bull. AAS, 199 126.14 Jodi Lamoureux, LBNL/NERSC June 2002

  10. Conclusions about Accelerators • Jury is still out on hadronic emission of TeV gamma rays. • CR are consistent with Fermi-acceleration but identifying localized sources is hard. • Photons reveal a number of possible sites… pulsars, AGN, GRB, SN remnants • So, what do we expect in the way of neutrinos? Jodi Lamoureux, LBNL/NERSC June 2002

  11. Anatomy of High Energy Neutrino Sources • Assume accelerated protons are impinging on a target of photons or protons. • Proton must interact min path*r = column density • Decay: n, p+ and p0 max r or path < decay length • Escape: nm , g and p max path*r Survival Probability ~ exp[-s(p + gX)*path*r] • p + g p+ + X •  m+ + nm •  nm + e+ + ne • p + g  p0 + X •  g + g • p + g  n + X •  p + e- +ne Jodi Lamoureux, LBNL/NERSC June 2002

  12. Anatomy of High Energy Neutrino Sources • WB Bound & MPR Bound • GZK • AGN Jet ? • Regions: • CR don’t interact • CR  p, g ,n • CR  g ,n • CR  n Hidden Sources • GRB ? Jodi Lamoureux, LBNL/NERSC June 2002

  13. Anantomy of High Energy Neutrino Sources • RX J1713.7-3946 • Not included in this view: • Hydrodynamics, magnetic shocks, local density variations, heavy ions and serendipitous source configurations. • Energy budgets Jodi Lamoureux, LBNL/NERSC June 2002

  14. Astrophysical Muon Neutrino Flux Albuquerque, Lamoureux, Smoot, hep-ph/0109177 • Diffuse flux: WB, MPR, GZK, galaxy Atmospheric nm • Point sources: AGN, Sgr-A, galactic center, RX-J1713.7-3946 Background * 1 deg/20,000 deg • Variable sources: GRB Background * 1 deg/20,000 deg * time coincidence factor. En dFn/dEn (km-2 yr-1 sr-1) TeV PeV EeV Jodi Lamoureux, LBNL/NERSC June 2002

  15. Oscillations & Muon Neutrino Flux Albuquerque, Lamoureux, Smoot, hep-ph/0109177 • Astrophysical Sources are far enough away that that flavors mix… nm:ne:nt 2 : 1 : 0 w/o osc 1 : 1 : 1 with osc • Atmospheric nm are produced locally and oscillations reduce the flux by less than 10%. En dFn/dEn (km-2 yr-1 sr-1) TeV PeV EeV Jodi Lamoureux, LBNL/NERSC June 2002

  16. Detecting Neutrinos 101 • Deep Inelastic Scattering • Charge current nm + p m + X ne + p e + X • Neutral current • + p n + X • Neutrino flux is attenuated as it passes through the earth. Albuquerque, Lamoureux, Smoot, hep-ph/0109177 COS(qz) = 0 COS(qz) = 1 COS(qz) Jodi Lamoureux, LBNL/NERSC June 2002

  17. Detecting Muons 101 Contained Through-going • Muon energy is ~80% of neutrino energy • Degrades in transit. • Measured through radiation deposited in the detector Jodi Lamoureux, LBNL/NERSC June 2002

  18. Muon Radiation 101 Albuquerque, Lamoureux, Smoot, hep-ph/0109177 • Muons radiate energy as they travel through ice. • Cerenkov light is a small fraction of the ionization component described by Bethe-Bloch equation. • Above 1 TeV other processes dominate: Bremstraahlung Photons Electron Pairs Photo-nuclear • Linear energy relation • Resolution has long tail Jodi Lamoureux, LBNL/NERSC June 2002

  19. Up-going Muon Flux in an Ideal km2 Detector (w/o oscillations) Albuquerque, Lamoureux, Smoot, hep-ph/0109177 Diffuse flux as a function of energy deposited in the detector. • Km2 detector is sensitive to 1/3rd of WB limit after 1 yr. 1/5th of WB limit after 2-3 yrs • If diffuse flux is comes from <10 sources, Km2 detector will identify them. GRB: Atm flux/(20000*DT) = back-free 15 events/year Sagittarius A East • 0 to 40 events/year at Mediterranean latitudes. RX J1713.7-3946 • 12 events/year Southern hemisphere Jodi Lamoureux, LBNL/NERSC June 2002

  20. UHE Muon Flux in an Ideal Km2 Detector • GZK n have Ultra High Energy • Above the horizon at EeV. • Radiated energy is enormous. • Without reconstructing tracks: number of photons in the detector gives lower limit to muon energy. • Effective area grows with energy 1 km2 @ E=1015 GeV 8 km2 @ E=1020 GeV • Fewer than 0.5 events/(km2 yr) expected from GZK. Engel, Stanev, astro-ph/0101216 EeV Jodi Lamoureux, LBNL/NERSC June 2002

  21. Recent Experimental Searches • AMANDA • Preliminary Muon Neutrino E-2 flux Veff ~ 0.01 km2@ TeV Hill & Leuthold, ICRC 2001 • All-flavor E-2 limits from cascades Veff ~ 0.002 km3 @ TeV Cowen, Neutrino 2002 Conf… paper submitted this week • RICE • Radio-Cerenkov E-2 flux Veff ~ 1+-0.5 km2 @ EeV Kravchenko et al. astro-ph/0206371 • Super-K • Neutrinos from GRB Fukuda et al. astro-ph/0205304 Jodi Lamoureux, LBNL/NERSC June 2002

  22. Summary of Experimental Results Jodi Lamoureux, LBNL/NERSC June 2002

  23. Conclusions • Astrophysical sources: • WB bound for CR inspired neutrino sources is conservative. • The CR spectrum does not necessarily imply a significant neutrino flux. • GRB, AGN, pulsars & SN remnants are possible hadron acceleration sites. • Hadronic photons (p0 g + g) compete with sychrotron & inverse compton to explain HE photons • Hidden sources aren’t inspired by experimental observations, but there is phase-space for En up to ~EeV. • Ideal Km3 detector will be able to discover: • Astrophysical ~E-2 fluxes down to 1/3 WB bound after 1 year. (with 100% duty cycle and reasonable energy resolution) • Models of GRB, Sgr-A, RX J1713.7-3946 (in “up-going” hemisphere) • UHE neutrinos (0.5 event/km2 yr), but may be detected from half a kilometer outside a detector in ice. • Neutrino detection would settle HAD/EM acceleration debate and possibly localize sources CR. • The search is on in a variety experimental venues. Jodi Lamoureux, LBNL/NERSC June 2002

  24. Photon Transport 101 • Cerenkov Light • PMTs are sensitive to 300 nm to 600 nm wavelengths • Muons and secondaries radiate Cerenkov light. • Cascades – tracks radiate Cerenkov light. Hadronic component is 0.8*<EM>. • Absorption length ~100 m • Effective scattering length ~25 m • Light is isotropized well before it is absorbed. • To first order, sampling is insensitive to geometric position or PMT orientation. • Current arrays sample a very small fraction of the total Cerenkov light… Total PMT area/detector surface area ~ 10-5 J. Ahrends, et. al,submitted PRD Jodi Lamoureux, LBNL/NERSC June 2002

  25. Atmospheric Neutrinos in AMADNA J. Ahrends, et. al, astro-ph/0205109 Jodi Lamoureux, LBNL/NERSC June 2002

  26. Atmospheric Neutrinos in AMANDA • Primary quality cuts: • Likelihood of track fit high • High fraction of unscattered hits • Long track length • Hits spread smoothly along track • Hits aren’t spherically distributed • Low prob of being down-going J. Ahrends, et. al, astro-ph/0205109 Jodi Lamoureux, LBNL/NERSC June 2002

  27. Atmospheric Neutrinos in AMANDA J. Ahrends, et. al, astro-ph/0205109 • At cut level 7: • 204 candidates with 10% background • Rate is 0.65 (+0.65 –0.3) times the predicted atmospheric neutrino rate. • Angular distributions of events are consistent with Atmospheric Neutrinos Vertical Up-going Horizon J. Ahrends, et. al, astro-ph/0205109 Jodi Lamoureux, LBNL/NERSC June 2002

  28. Atmospheric Neutrino Spectrum in AMANDA J. Ahrends, et. al, astro-ph/0205109 Simulated Energy Threshold: AMANDA measures flux in the energy range: 66 GeV < En < 3.4 TeV En = 50 GeV Em (center) = 20 GeV Jodi Lamoureux, LBNL/NERSC June 2002

  29. Astrophysical Neutrino Limit 0 10 20 30 40 50 60 70 80 90 100 Jodi Lamoureux, LBNL/NERSC June 2002

  30. Atmospheric Neutrino Spectrumin AMANDA • Preliminary AMANDA limit: • dN/dEn < 10-6 En-2 • (cm-2s-1sr -1GeV -1) • Rules out the most optimistic MPR power-spectrum limit. G. Hill ,ICRC 2001 Jodi Lamoureux, LBNL/NERSC June 2002

  31. The Future… IceCube • IceCube: 80 strings 60 PMTs/string Depth: 1.4-2.4 Km Jodi Lamoureux, LBNL/NERSC June 2002

  32. IceCube Concept IceTop AMANDA South Pole Skiway 1400 m 2400 m • IceTop: 2 PMTs in a “pool” at the top of each string. 3D air-shower detector Jodi Lamoureux, LBNL/NERSC June 2002

  33. Simulated IceCube Events 10 TeV Muon 375 TeV Electron PeV Tau 6 PeV Muon Jodi Lamoureux, LBNL/NERSC June 2002

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