Beam-forming and matched filter techniques for the underwater acoustic detection of UHE neutrino

Abstract

The search for UHE neutrinos is one of the most promising fields in astroparticle physics. The experimental techniques proposed to identify cosmic neutrino signatures are mainly three: the detection of Cherenkov blue light originated by charged leptons (electrons, positrons, muons and tauons) from neutrino interaction in water or ice; the detection of acoustic waves produced by neutrino energy deposition in water, ice or salt; the detection of radio pulses following neutrino interaction in ice or salt. Due to the expected neutrino fluxes (≈10 −8 E 2 Gev/cm 2 s sr) and due to their extremely low interaction cross-section (≈10 −32 cm 2 at 10 20 eV), huge target volumes (≈km 3) are required to detect them. Acoustic detection of neutrino is a very suitable technique since the sound attenuation length, at the frequency of interest, is of the order of km. Due to the small amplitude of the expected neutrino bipolar signal (≈10 mPa), it is mandatory to develop an effective algorithm that increases the signal to noise ratio (SNR). In the present work a combination of matched filter, applied to each single hydrophone, and a beam-forming technique applied to a small array of hydrophones is proposed. The matched filter is a well-known technique of signal processing that maximizes the SNR in the presence of white noise. Beam forming is a signal-processing technique used in sensor arrays for directional analysis; the signals from different sensors are combined in such a way that pressure waves arriving from a specific direction are coherently summed. Preliminary results on simulated data will be shown.