Results from a Study of Acoustic Ultrahigh- energy Neutrino - - PowerPoint PPT Presentation

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results from a study of acoustic ultrahigh energy

Results from a Study of Acoustic Ultrahigh- energy Neutrino - - PowerPoint PPT Presentation

Feb 20, 2023 40 likes •373 views

Results from a Study of Acoustic Ultrahigh- energy Neutrino Detection (SAUND) http://hep.stanford.edu/neutrino/SAUND/ Justin Vandenbroucke justinav@socrates.berkeley.edu September 13, 2003 Stanford University Workshop on Acoustic Cosmic Ray

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Results from a Study of Acoustic Ultrahigh- energy Neutrino Detection (SAUND)

http://hep.stanford.edu/neutrino/SAUND/

Justin Vandenbroucke

justinav@socrates.berkeley.edu

September 13, 2003 Stanford University Workshop on Acoustic Cosmic Ray and Neutrino Detection

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Stanford University Justin Vandenbroucke September 13, 2003

Andros Island, The Bahamas

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Stanford University Justin Vandenbroucke September 13, 2003

AUTEC hydrophone array

SAUND

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Stanford University Justin Vandenbroucke September 13, 2003

Site 3

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Site 3

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DAQ system

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Calibration sources

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21 Events per lightbulb

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Light bulb positions and energies reconstructed

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Light bulb positions and energies reconstructed

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Detection contours under typical noise conditions

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Detection contours under typical noise conditions (zoomed in)

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Pancakes can be good

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AUTEC SVP

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Refraction is significant beyond 1 km

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Refraction is significant beyond 1 km

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Refracted pancake (undetected)

300 m deflection!

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Refracted pancake (detected)

100 m deflection

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Stanford University Justin Vandenbroucke September 13, 2003

Localization achieved

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Localization → energy reconstruction

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Cut 1: Digital Filter

τ = 10 µs

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Stanford University Justin Vandenbroucke September 13, 2003

Cut 3: Five-phone coincidence

Require 1) Events obey causality: Pairwise, times are within coincidence window: tij < c * dij 2) Geometry consistent with pancake (2D circle) shape: accepted: rejected:

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Stanford University Justin Vandenbroucke September 13, 2003

Example of a five-phone event

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Example of a five-phone event

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Stanford University Justin Vandenbroucke September 13, 2003

Cuts 4a and 4b: Characteristic Frequency and Number of Periods

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Stanford University Justin Vandenbroucke September 13, 2003

Cut 4c: Diamond Events

frequent but easily rejected with a matched filter (online?)

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Cut 5: Adaptive threshold

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Cut 6: Pancake shape constrains effective volume

(bad news and good news)

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Cut 7: Threshold crossings

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Stanford University Justin Vandenbroucke September 13, 2003

Background rejection

Cut Events passing cut (Run II, 163 days integrated livetime) 1) Filter trigger 40 million single-phone events 2) Electronic noise 25 million single-phone events 3) 5-phone coincidence 5 million combinations 4) Waveform analysis 3 thousand combinations a) Periods < 4 b) 20 kHz < freq < 40 kHz c) Diamond metric < 0.7 5) Threshold <= 0.024 6) 5-phone localization 300 combinations 7) Threshold crossings < 2 combinations (online, offline)

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Stanford University Justin Vandenbroucke September 13, 2003

What have we learned?

Refraction cannot be neglected for > ~ 1 km rays
Travel times are not significantly affected, but
Arrival direction and radiation envelope are (deflection)
Phones on sea floor are bad
Ray tracing necessary for localization
csound = clight / 200,000 !!
Coincidence is a very weak requirement → combinatorics
3D localization demonstrated
10 m resolution attained
Array geometry important; planar array is worst case

(but our signal is planar...)

Pancake shape a powerful requirement (despite decreased volume)
Impulsive backgrounds at 1021 eV exist but can be rejected
Energy threshold is very high (1021 eV) with 1.5 km spacing and current triggers

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Stanford University Justin Vandenbroucke September 13, 2003

Whats next?

Analysis

Rigorous Monte Carlo efficiency check
Final flux limits

SAUND-II

More phones, more volume, more computer processing
Improve adaptive threshold algorithm
Build coincidences online
Optimize cut strategy
Lower energy threshold (one order of magnitude reasonable)
Push to the Gaussian noise floor

Beyond (other arrays)

100-500 m spacing?
better geometry?
better noise environment?