Flux Limits for Ultra-High Energy Neutrinos Physics Radio pulse, Ev>1022 eV NuMoon@WSRT, results NuMoon@LOFAR, status Olaf Scholten KVI, Groningen August 2011 ICRC, Beijing

Principle of the measurement Small flux ≈ 1 / km2 / sr / century above 1020 eV! Lunar area ≈ 107 km2 Cosmic ray or neutrino Detection: Westerbork/LOFAR antennas 107 km2 100MHz Radio waves Proefje door Tjalling Nijboer en Martin Stokroos: Statische electriciteit van wrijfstok is hoorbaar via radio ontvanger op de middengolf. Principle of the measurement August 2011 ICRC, Beijing

Askaryan effect: Coherent Cherenkov emission ~10 cm ~2 m Cosmic ray shower Wave front Recent evidence: Askaryan effect in CR airshowers K.D. de Vries, AstroParticle Physics & arXiv:1008.3308 H. Schoorlemmer for PAO, ARENA 2010 Important magnitudes: Leading cloud of electrons, v  c Typical size of order 10cm Coherent Čerenkov for ν  2-5 GHz cos θc =1/n , θc=56o for ∞ shower length Length of shower, L  2-3 m strong angular spreading for ν  100 MHz

Cosmic rays, Position on Moon Calculations for Ecr=4 1021 eV 3 GHz 100 MHz 100 MHz 3 GHz With decreasing ν increasing probability: ∫ over surface Moon Detection probability  ν-3 rim inside O.S. et al, Astropart.Phys. 26 (2006) 219

Results WSRT observations No pulse of 240kJy seen in 46.7 h data  90% confidence limit on neutrino flux O.S. et al, PRL 103(2009)191301 Buitink, et al., A&A 521, A47 (2010).

NuMoon Experiment @ LOFAR New generation of radio-telescopes, many (3000) simple wire antennas Total collecting area  0.25 km2 Cover whole moon, Sensitivity 25 times better than WSRT. Band: 115-240 MHz Multiple tied-array beams August 2011 ICRC, Beijing

Nano-second pulse finding Determine power over threshold in sliding window of length N Aim: Determine optimum window length N Threshold: set to 1 accidental count per minute Correcting for atmospheric dispersion, with accuracy ΔSTEC TECU Strength of pulse added to background in units of noise power August 2011 ICRC, Beijing Optimum: N=10-15

Beam shape depends on station layout Station layout: 4 km x 4 km Beam profile φ=210o φ=120o Δφ Side-lobes suppressed Max: Δφ= 0.062o @ φ=120o Min: Δφ= 0.056o @ φ=210o Conclusion: need fewer than 50 beams to cover visible Lunar surface August 2011 ICRC, Beijing

Background noise Radio stations: narrow-band RFI  can easily be filtered out Human activity: Broad-band RFI  potential problem ! Data: 8 half stations for 10 seconds direction Virgo A Amplitude spectrum Gaussian  No problems expected Pulsed (broad-band )RFI suppressed further by anti-coincidence filter between the different radio beams August 2011 ICRC, Beijing

Neutrinos Conclusion: With LOFAR able to LOFAR, 1 week Conclusion: With LOFAR able to reach sensitivity level W-B estimate

Conclusions NuMoon Future: NuMoon @ WSRT: New limit for E > 1023 eV NuMoon @ LOFAR: Sensitive to W-B flux Future: NuMoon @ SKA Extend limit to lower E Improve Flux limit NuMoon NuMoon collaboration: O.S., Stijn Buitink, Heino Falcke , Clancy James, Maaijke Mevius, Ben Stappers, Kalpana Singh, Richard Strom , Sander ter Veen August 2011 ICRC, Beijing

Cosmic rays Pierre Auger model-independent limit Pierre Auger extrapolation S. ter Veen, et al. , Phys. Rev. D 82, 103014 (2010). August 2011 ICRC, Beijing