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Results from SAUND Study of Acoustic Ultra-high-energy Neutrino Detection http://saund.stanford.edu

Results from SAUND Study of Acoustic Ultra-high-energy Neutrino Detection http://saund.stanford.edu. Justin Vandenbroucke University of California, Berkeley justin@amanda.berkeley.edu ARENA Workshop, DESY-Zeuthen, May 18, 2005. The T ongue o f t he O cean ( TOTO ). The SAUND-1 array.

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Results from SAUND Study of Acoustic Ultra-high-energy Neutrino Detection http://saund.stanford.edu

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  1. Results from SAUNDStudy of Acoustic Ultra-high-energy Neutrino Detectionhttp://saund.stanford.edu Justin Vandenbroucke University of California, Berkeley justin@amanda.berkeley.edu ARENA Workshop, DESY-Zeuthen, May 18, 2005

  2. The Tongue of the Ocean (TOTO) Justin Vandenbroucke ARENA Workshop May 18, 2005

  3. The SAUND-1 array 7 hydrophones on sea floor, spacing ~1.5 km Justin Vandenbroucke ARENA Workshop May 18, 2005

  4. Integrated livetime Physics run (147 days) Commissioning run (48 days) Fraction of up days Fraction of all days Justin Vandenbroucke ARENA Workshop May 18, 2005

  5. Livetime at each adaptive-threshold value “quiet” times used for analysis Justin Vandenbroucke ARENA Workshop May 18, 2005

  6. Acoustic pulse simulation Expansion of basic kernel written by N. Lehtinen Given a detector position (r,) relative to the shower, calculate P(t): Use Learned’s prescription to integrate over the energy density of the shower (in the time domain) The code can simulate water, ice, and salt. Input: X0, Ecrit, RMoliere, vsound, Cp,  At this energy, LPM effect lengthens electromagnetic shower to O(1 km), so assume hadronic contribution dominates Use hadronic shower parametrization (gamma functions), based on Alvarez-Muñiz & Zas, Phys. Lett. B 434 (1998) (includes LPM effect on sub-showers) Assume constant inelasticity: Ehad.sh = 0.2 E for all flavors, both NC and CC Apply sea-water absorption directly in the time domain using Learned’s “smearing function” technique Justin Vandenbroucke ARENA Workshop May 18, 2005

  7. Simulated neutrino pulses 1050 m transverse distance from shower longitudinal distance z forward from shower max Eshower = 1020 eV t (s) Justin Vandenbroucke ARENA Workshop May 18, 2005

  8. Pancake contours Labeled by Log10(E/GeV) Justin Vandenbroucke ARENA Workshop May 18, 2005

  9. Over several km, refraction is significant! unrefracted (+5 to -5 degrees) refracted Justin Vandenbroucke ARENA Workshop May 18, 2005

  10. How to calculate refracted ray paths See Boyles, “Acoustic Waveguides: Applications to Oceanic Science” for a nice algorithm: • - Divide ocean in layers, but don’t use Snell’s law directly (zeroth order, c constant in each layer) • Use c = c0 + h*z (first order, c linear in each layer) • In such layers, paths follow arcs of circles: • In ocean, Rcurvature is O(100 km) >> path lengths, so do we care? • Yes: Deviation is quadratic in path length: y x ray emitted horizontally So for R=100 km, x=5 km: y=125 m > pancake thickness Justin Vandenbroucke ARENA Workshop May 18, 2005

  11. Neutrino pancakes are refracted E = 3 x 1021 eV Justin Vandenbroucke ARENA Workshop May 18, 2005

  12. Shadow zone due to refraction Rays from shadow zone cannot reach central phone Justin Vandenbroucke ARENA Workshop May 18, 2005

  13. Focusing/defocusing due to refraction? Slight focusing. Contours give intensity focusing factor for various source locations as seen at central hydrophone. Justin Vandenbroucke ARENA Workshop May 18, 2005

  14. Event topology cuts Require: 1) Events obey causality: tij dij /vsound + 10% 2) Geometry consistent with pancake (flat circle!) shape: No hit Hit Accepted: Rejected: Justin Vandenbroucke ARENA Workshop May 18, 2005

  15. Source localization: 2 algorithms • 1) Analytical • Time-difference-of-arrival, TDOA (for homogeneous media): • Each independent pair of receivers constrains source to hyperboloid • 4 receivers gives 3 hyperboloids intersecting in 0, 1, or 2 source points • 5 receivers gives unambiguous location (in the case of 2 solutions) • An exact analytical solution exists using d = ct for each receiver: • - Combine them into a matrix equation and use Singular Value Decomposition [Spiesberger & Fristrup, American Naturalist 135, 1 (1990)] But in ocean c = c(z) • 2) Grid-based • - For grid of source locations, use measured c(z) to calculate ray path to each receiver location, integrate travel time • From source-receiver times for N receivers, calculate N-1 independent time differences of arrival • Compare to measured time differences, best match gives best grid point • Linearly interpolate tijgrid locally around best grid point Justin Vandenbroucke ARENA Workshop May 18, 2005

  16. Localization: Monte Carlo and Data (Top View) • 1014 GeV MC • 1015 GeV MC • 1016 GeV MC  data Justin Vandenbroucke ARENA Workshop May 18, 2005

  17. Monte Carlo and Data (Radial View) • 1014 GeV MC • 1015 GeV MC • 1016 GeV MC  data Justin Vandenbroucke ARENA Workshop May 18, 2005

  18. Background Rejection Cut Events remaining 1. Online triggers: a) Digital filter ..................................................................... 64.6 M b) Correlated noise ............................................................ 20.2 M 2. Quality cuts: a) Offline rethresholding..................................................... 7.23 M b) Offline quiet conditions.................................................. 2.60 M c) ∆t0 > 1 ms .............................................................…..…. 2.56 M 3. Waveform analysis: a) Remove spikes ........................................................….... 2.03 M b) Remove diamonds..................................................…..... 1.96 M c) fe > 25 kHz..........................................................….….…. 1.92 M 4. Coincidence building: a) Coincidence ..........................................................……....... 948 b) Localization convergence.......................................……….. 79 5. Geometric fiducial region….………………………………........0 Justin Vandenbroucke ARENA Workshop May 18, 2005

  19. Flux limits SAUND not optimized for neutrinos. A/B represent 1-year limits from hypothetical large arrays (367 1.5-km strings, spaced 0.5/5 km apart) Justin Vandenbroucke ARENA Workshop May 18, 2005

  20. Conclusions The first large-area, large-livetime search for acoustic neutrino signals has been completed. Code has been written to simulate P(t) at arbitrary location, with absorption, for various media. DAQ, triggering, adaptive thresholding, noise rejection, and reconstruction strategies have been developed. Over multi-km distances in the ocean, refraction is important! A neutrino flux limit has been calculated. It is not competitive, but is from an entirely different signal production and detection mechanism: complements the radio limits. The ocean has been characterized as a target material, but there is room for improvement: phase information, signal processing, analysis techniques, environmental (site) variation. Needs SAUND-2 and other efforts! Ethr in the ocean seems to be unavoidably high - are there any fluxes here? Onward to other materials! Justin Vandenbroucke ARENA Workshop May 18, 2005

  21. Academic: G. Gratta (Stanford) N. Lehtinen (Stanford) S. Adam (Stanford, now Cornell) T. Berger (Scripps) M. Buckingham (Scripps) Y. Zhao (Stanford) J. Vandenbroucke (Stanford, now Berkeley) with help from N. Kurahashi (Stanford) US Navy: D. Belasco J. Cecil D. Deveau D. Kapolka T. Kelly-Bissonnette The SAUND-1 Collaboration: More information: see http://saund.stanford.edu and Vandenbroucke et al, ApJ 621:301-312 (2005) Justin Vandenbroucke ARENA Workshop May 18, 2005

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