Study of Acoustic Ultra-high energy Neutrino Detection

March 1, 2005:
"Experimental Study of Acoustic Ultra-High-Energy Neutrino Detection"
Astrophysical Journal, 621:301-312 PDF
(high-resolution jpeg's of the figures available here)

An International ARENA (Acoustic and Radio EeV Neutrino detection Activities)
will be held May 17-19, 2005
at DESY, Zeuthen, Germany 

The First Informal Mini-workshop on Acoustic Cosmic Ray and Neutrino Detection
was held at Stanford University, September 13-14, 2003.
Slides are available.

(shower diagram)

Figure 1. The particle shower and the acoustic pulse.

Description of the project

Understanding the highest energy cosmic rays represents one of the most challenging fields of modern physics. To date some 12 cosmic ray events, presumably protons, have been observed with energies in excess of 10^20 eV. The gamma photons and protons inevitably generate the UHE neutrinos in cosmic beam dumps. The weakly interacting neutrinos, unlike gamma photons and protons, can reach us from distant sources and therefore are a possible invaluable instrument of high-energy astrophysics.

Due to a low interaction cross-section, it is hard to detect a UHE neutrino in atmosphere. We proposed an acoustic technique of search for UHE (i.e., with energy >1 EeV=10^18 eV) neutrino in ocean water using an underwater hydrophone array. It will complement in the high-energy region the other techniques, such as using Cherenkov light under water and in ice, which are currently optimized for the TeV-EeV energy region. The neutrino interacting in water creates a particle shower, which has a detectable hadronic part and (in the case of electron neutrino) electromagnetic part, which is elongated due to Landau-Pomeranchuk-Migdal effect. As the shower energy is deposited in the water, the thermal expansion generates an acoustic pulse, which is then propagated (due to the elongated source shape) mostly perpendicularly to the shower axis, as shown in Figure 1. The signal arriving at the detector is predicted to be well within the sensitivity of good quality hydrophones, depending on the relative position of the hydrophone and the shower. The acoustic technique also includes optimal detection in the background gaussian noise, which is due to waves on the ocean surface and random thermal excitations. We studied the detection efficiency and concluded that the array of ~100 hydrophones can have sufficient sensitivity for detection of neutrinos with energies >10^20 eV.

(detector diagram)

Figure 2. The configuration of hydrophones.

During the summer of 2001, an experiment was set up at the Atlantic Undersea Test and Evaluation Center (AUTEC) hydrophone array, using a computer with a NI data acquisition card connected to a group of 7 hydrophones that make up a hexagonal pattern. The primary purpose is to analyze the feasibility of a larger experiment, and to work out a technique to filter the coherent artificial and animal noise. The acoustic data stream was analyzed in real time, selecting only the data according to the amplitude and the response of the filter matched to the shape of the UHE neutrino signal. At the present time, the data acquisition is continuing and we are working on the analysis of the data.

Field trips

(toto satellite image)

Figure 3. The Tongue of the Ocean (TOTO) - where the AUTEC hydrophone array is located.


(TOTO picture)

Figure 4. The view of TOTO from a helicopter.



    The slides below give overviews of SAUND.  They are mostly different versions of similar slides (most recent listed first).





Further Reference


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