Ultra High Energy neutrinos in Ice Cube and
Ultra High Energy neutrinos in Ice. Cube and future detection methods Shirit Cohen, LPHE, EPFL SPS meeting 08, Genève 26. 03. 08 Shirit Cohen, UHE neutrinos in Ice. Cube
Outline § Motivation § Ice. Cube detection potential of Ultra High Energy (UHE) neutrinos § Acoustic and radio signals § Current R&D efforts for acoustic detection § Activities at EPFL 26. 03. 08 Shirit Cohen, UHE neutrinos in Ice. Cube 2
Ultra High Energy neutrinos in Ice. Cube § GZK effect - high energy protons interact with CMB photons: or Cosmic ray flux § Auger & Hi. Res show drop GZK neutrinos § Detection of both will allow to identify sources, determine Particle Data Group injection spectrum and creation mechanism 26. 03. 08 Shirit Cohen, UHE neutrinos in Ice. Cube GZK effect? 3
UHE neutrinos in Ice. Cube § Search for GZK neutrinos in IC 9 § No events found, as expected from models § Empirical model of the background § For IC 80 expect 0. 1 -10 events a year § Well above bg level Fluxes at Ice. Cube depth P rel im ina ry Atmospheric muon bundles with/out GZK cut-off If they are there, we should see them! But 26. 03. 08 rates will not be sufficient Shirit Cohen, for UHE neutrinos in Ice. Cube characterizing the energy spectrum Ice. Cube 5 y sensitivity limit 4
Neutrino-induced cascades produce 3 signals in dense media ice (3) Askaryan acoustic pancake ~ few km? interaction hadronic shower (2) Askaryan effect, coherent radio cherenkov emission, ~1 km (1) Optical Cherenkov cone (2) ~100 m Hybrid detection is feasible only in ice 26. 03. 08 Larger attenuation length for radio and acoustic Cohen, UHE neutrinos in instrumented array!5 build a. Shirit larger, sparser Ice. Cube
Current research activities: SPATS and more § Measure vsound in SP ice § Extract attenuation length of acoustic signal § Understand noise sources anthropogenic noise, transients § Detector R&D signal A B 26. 03. 08 Shirit Cohen, UHE neutrinos in Ice. Cube 6
Speed of sound @ SP ry a n i m li e r P signals at different depths, from one string to another, for different string pairs Within error, sound speed independent of depth Work in progress 26. 03. 08 Shirit Cohen, UHE neutrinos in Ice. Cube 7
Attenuation analysis: ln(amplitude*distance) vs. distance ry a in m i l e r P geometric diffusion 1/r, exp. att. from ice systematic uncertainties astro-ph/07082089 26. 03. 08 Shirit Cohen, UHE neutrinos in Ice. Cube 8 Work in progress
Activities at LPHE EPFL § Test setup designed for directional measurements § Emitter developed and tested, installed at SP § Sensor development, increasing sensitivity and minimizing self-noise level § Analyzing data recorded by SPATS 26. 03. 08 New sensor in development Shirit Cohen, UHE neutrinos in Ice. Cube 9
Setup Support structure for two sensors and one emitter 1, 5 m Motors polar+ azimutal Calibrated hydrophone Emitter Acoustic sensor § Water tank § Relative orientation & distance between transmitter and sensor § Automated mechanics controlled using a 26. 03. 08 Shirit Cohen, UHE neutrinos in Lab. View program Ice. Cube 10
Proposal for HE Ice. Cube extension 3 km 0 0 ~1 - cross-calibration - background rejection - event reconstruction - shallow, narrow holes - simple electronics detect 10’s of GZK ’s a year, ~50% hybrid 26. 03. 08 Shirit Cohen, UHE neutrinos in Ice. Cube 11 astro-ph/0512604
Summary § As Ice. Cube installation proceeds we expect to see the first UHE neutrino event § Feasibility studies of acoustic neutrino detection at the SP ice are ongoing § EPFL is involved in both efforts 26. 03. 08 Shirit Cohen, UHE neutrinos in Ice. Cube 12
Backup slides 26. 03. 08 Shirit Cohen, UHE neutrinos in Ice. Cube
South pole noise level stable Gaussianshaped noise, decreasing with depth electronic, non man-made 26. 03. 08 Shirit Cohen, UHE neutrinos in Ice. Cube 14 astro-ph/07082089
Acoustic signal § Plot bipolar signal § Pressure of ~ 1 m. Pa for 1019 e. V neutrino at 1 km distance § Peak frequency 30 k. Hz 26. 03. 08 Shirit Cohen, UHE neutrinos in Ice. Cube 15
IC 9 GZK neutrino flux upper limit 26. 03. 08 Shirit Cohen, UHE neutrinos in Ice. Cube 16
- Slides: 16