1. 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 Justin Vandenbroucke University of California, Berkeley justin@amanda.berkeley.edu ARENA Workshop, DESY-Zeuthen, May 18, 2005

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

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

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

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

6. Justin Vandenbroucke ARENA Workshop May 18, 2005 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: X 0, E crit, R Moliere, v sound, C p,  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: E had.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

7. Justin Vandenbroucke ARENA Workshop May 18, 2005 Simulated neutrino pulses 1050 m transverse distance from shower longitudinal distance z forward from shower max E shower = 10 20 eV t (  s)

8. Justin Vandenbroucke ARENA Workshop May 18, 2005 Pancake contours Labeled by Log 10 (E /GeV)

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

10. Justin Vandenbroucke ARENA Workshop May 18, 2005 How to calculate refracted ray paths - Divide ocean in layers, but don’t use Snell’s law directly (zeroth order, c constant in each layer) - Use c = c 0 + h*z (first order, c linear in each layer) - In such layers, paths follow arcs of circles: - In ocean, R curvature is O(100 km) >> path lengths, so do we care? - Yes: Deviation is quadratic in path length: x y So for R=100 km, x=5 km: y=125 m > pancake thickness ray emitted horizontally See Boyles, “Acoustic Waveguides: Applications to Oceanic Science” for a nice algorithm:

11. Justin Vandenbroucke ARENA Workshop May 18, 2005 Neutrino pancakes are refracted E = 3 x 10 21 eV

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

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

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

15. Justin Vandenbroucke ARENA Workshop May 18, 2005 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)] 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  t ij grid locally around best grid point But in ocean c = c(z)

16. Justin Vandenbroucke ARENA Workshop May 18, 2005 Localization: Monte Carlo and Data (Top View) 10 14 GeV MC 10 15 GeV MC 10 16 GeV MC  data

17. Justin Vandenbroucke ARENA Workshop May 18, 2005 Monte Carlo and Data (Radial View) 10 14 GeV MC 10 15 GeV MC 10 16 GeV MC  data

18. Justin Vandenbroucke ARENA Workshop May 18, 2005 Background Rejection CutEvents 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) ∆t 0 > 1 ms.............................................................…..…. 2.56 M 3. Waveform analysis: a) Remove spikes........................................................….... 2.03 M b) Remove diamonds..................................................…..... 1.96 M c) f e > 25 kHz..........................................................….….…. 1.92 M 4. Coincidence building: a) Coincidence..........................................................……....... 948 b) Localization convergence.......................................……….. 79 5. Geometric fiducial region….………………………………........0

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

20. Justin Vandenbroucke ARENA Workshop May 18, 2005 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! E thr in the ocean seems to be unavoidably high - are there any fluxes here? Onward to other materials!

21. Justin Vandenbroucke ARENA Workshop May 18, 2005 The SAUND-1 Collaboration: 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. BelascoJ. Cecil D. DeveauD. Kapolka T. Kelly-Bissonnette More information: see http://saund.stanford.edu and Vandenbroucke et al, ApJ 621:301-312 (2005)