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Saltdome Shower Array: A GZK neutrino Detector Introduction

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Saltdome Shower Array: A GZK neutrino Detector Introduction

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  1. Saltdome Shower Array: A GZK neutrino Detector Introduction Peter Gorham University of Hawaii at Manoa P. Gorham, SLAC SalSA workshop

  2. (Ultra-)High Energy Physics of Cosmic rays & Neutrinos 40 yrs of 1018-20 eV CR data: • Origin unknown above 1019 eV • Energy: 107 times Tevatron • A paradox: No nearby sources, but physics excludes distant sources due to collisions with boosted (in c.m. frame) microwave background (GZK process) • Neutrinos at 1017-19 eV required by standard-model physics through the GZK process--observing them is crucial to resolving the GZK paradox galactic extragalactic • Observation of UHECR GZK cutoff feature by Auger still requires confirmation with GZK neutrino observations to verify GZK interactions P. Gorham, SLAC SalSA workshop

  3. Neutrinos: The only useful messengers at >PeV energies • Photons lost above 30 TeV:pair production on IR & mwave background • Charged particles:scattered by B-fields or GZK process at all energies • But the source energetics extend to 109 TeV ! Conclusion: • Study of the highest energy processes and particles throughout the universe requires PeV-ZeV neutrino detectors Region not observable In photons or Charged particles P. Gorham, SLAC SalSA workshop

  4. Particle Physics: Energy Frontier & Neutrinos • Well-determined GZK n spectrum becomes a useful beam • 10-300 TeV center of momentum particle physics • study large extra dimensions at scales beyond reach of LHC • n Lorentz factors of g=1018-21! • Measured flavor ratios ne:nm:ntcan • identify non-standard physics at source • Longest L/E for: sterile n admixtures & anomalous n decays Large extra dimensions Std. model GZK n Anchordoqui et al. Astro-ph/0307228 P. Gorham, SLAC SalSA workshop

  5. Particle Astrophysics/Cosmology • Cosmic ray Emax, the maximum acceleration energy • UHECR flux vs. redshift to z = 15-20 (eg. WMAP early bright phase, ) • Independent sensitivity to dark energy density • Exotic (eg. Top-down) sources; GUT-scale decaying relics P. Gorham, SLAC SalSA workshop

  6. What is needed for a GZK n detector? • Standard model EeV GZK n flux: <1 per km2 per day over 2p sr • Interaction probability per km of water = 0.2% • Derived rate of order 0.5 event per year per cubic km of water or ice  A teraton (1000 km3 sr) target is required! Problem: how to scale up from current water Cherenkov detectors • One solution: exploit the Askaryan effect: coherent radio Cherenkov emission • Particle showers in solid dielectric media yield strong, coherent radio pulses • Neutrinos can shower in many radio-clear media: air, ice, rock-salt, etc. • Economy of scale for a radio detector (antenna array + receivers) is very competitive for giant detectors P. Gorham, SLAC SalSA workshop

  7. Antenna array Saltdome Shower Array (SalSA) concept Salt domes: found throughout the world Qeshm Island, Hormuz strait, Iran, 7km diameter 1 2 3 Depth (km) 4 • Halite (rock salt) • La(<1GHz) > 500 m w.e. • Depth to >10km • Diameter: 3-8 km • Veff ~ 100-200 km3 w.e. • No known background • >2p steradians possible 5 Isacksen salt dome, Elf Ringnes Island, Canada 8 by 5km 6 7 • Rock salt can have extremely low RF loss:  as radio-clear as Antarctic ice • ~2.4 times as dense as ice • typical:50-100 km3 water equivalent in top ~3km ==>300-500km3 sr possible P. Gorham, SLAC SalSA workshop

  8. U.S Gulf coast salt domes • Salt dome demographics: • Several hundred known—some are good source of oil • Typical ~3-5 km diameters, 5-15 km deep • ~200 km3 water equiv. in top 3-5 km for many domes Hockley dome/mine Houston New Orleans P. Gorham, SLAC SalSA workshop

  9. Gulf coast salt domes • Texas, Louisiana, Mississippi all have dozens or even hundreds of domes • 3-4 km diameters, 5-10 km depths typical • Often explored for oil that is trapped on flanks P. Gorham, SLAC SalSA workshop

  10. Tehuantepec, Mexico • These salt domes have similar ages, structure, composition, to Louisana/Texas domes • Several are very large • 7 by 4 km • 6 by 5 km • Probably there are many more than shown here P. Gorham, SLAC SalSA workshop

  11. Utah/Colorado salt structures • Utah, Colorado contains a region of salt diapirs • Many “anticlines”, several domes • Beds are relatively shallow, salt formations are young • Salt is relatively impure with more clay & brine entrained P. Gorham, SLAC SalSA workshop

  12. In situ salt dome examples of attenuation P. Gorham, SLAC SalSA workshop

  13. Borehole radar on dome flank • Pine Prairie dome, LA northern extreme of Louisiana salt dome region • Holser et al 1972 used dipole & helix antennas at 230MHz in a 5” diameter sonde to map the flank of the dome (1 microsec pulses) • Most data within 150m of edge of dome (anhydrite content usually increases) • Saw attenuation lengths of 60-220m, ~100m on average • Flank location confirmed by retrieved samples when flank was intercepted P. Gorham, SLAC SalSA workshop

  14. Humble dome: oil-rich caprock • 4.8 km wide, salt level begins at 600m depth, thick caprock • Town of Humble is centered on dome! • Humble Oil--now known at Exxon!! P. Gorham, SLAC SalSA workshop

  15. Examples of salt dome halite purity P. Gorham, SLAC SalSA workshop

  16. SalSA simulations • A 2.5 km3 array with 225 m spacing, 122=144 strings, 123=1728 antenna nodes, 12 antennas per node, dual polarization ==> 290 km3 sr at 1 EeV • Threshold 1017 eV, few 100s antennas hit at 1 EeV, >1000 hits at 10 EeV • Rate: at least 10 events per year from rock-bottom minimal GZK predictions P. Gorham, SLAC SalSA workshop

  17. Existing Neutrino Limits and Potential Future Sensitivity • RICE limits for 3500 hours livetime • GLUE limits~120 hours livetime • ANITA sensitivity, 3 flights: • nm & neincluded, full-mixing parameterized • ~8 to 30 GZK neutrinos • IceCube • Auger • SalSA sensitivity, 3 yrs live • Similar to ANITA calcs • 70-230 GZK neutrino events!! P. Gorham, SLAC SalSA workshop

  18. Roadmap to a GZK neutrino detector • Site investigations: needed now • Site surveys: core samples on select domes (within 1 year) • Prototype arrays (3-4 strings) in 2 or more domes to test propagation (next 2 years) • Final site selection & construction timed to begin with announcements by ANITA,IceCube, Auger of GZK neutrinos, 2007-2008! P. Gorham, SLAC SalSA workshop