Volume 521, October 2010
|Number of page(s)||12|
|Published online||19 October 2010|
Constraints on the flux of ultra-high energy neutrinos from Westerbork Synthesis Radio Telescope observations
Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA e-mail: email@example.com
2 Department of Astrophysics, IMAPP, Radboud University, 6500 GL Nijmegen, The Netherlands
3 Kernfysisch Versneller Instituut, University of Groningen, 9747 AA Groningen, The Netherlands
4 ASML Netherlands BV, PO Box 324, 5500 AH Veldhoven, The Netherlands
5 CSIRO - Astronomy and Space Science, PO Box 76, Epping NSW 1710, Australia
6 Kapteyn Institute, University of Groningen, 9747 AA Groningen, The Netherlands
7 ASTRON, 7990 AA Dwingeloo, The Netherlands
8 School of Physics & Astronomy, Alan Turing Building, Univ. of Manchester, Manchester M13 9PL, UK
9 Astronomical Institute A. Pannekoek, University of Amsterdam, 1098 SJ, The Netherlands
Accepted: 18 February 2010
Context. Ultra-high energy (UHE) neutrinos and cosmic rays initiate particle cascades underneath the Moon's surface. These cascades have a negative charge excess and radiate Cherenkov radio emission in a process known as the Askaryan effect. The optimal frequency window for observation of these pulses with radio telescopes on the Earth is around 150 MHz.
Aims. By observing the Moon with the Westerbork Synthesis Radio Telescope array we are able to set a new limit on the UHE neutrino flux.
Methods. The PuMa II backend is used to monitor the Moon in 4 frequency bands between 113 and 175 MHz with a sampling frequency of 40 MHz. The narrowband radio interference is digitally filtered out and the dispersive effect of the Earth's ionosphere is compensated for. A trigger system is implemented to search for short pulses. By inserting simulated pulses in the raw data, the detection efficiency for pulses of various strength is calculated.
Results. With 47.6 hours of observation time, we are able to set a limit on the UHE neutrino flux. This new limit is an order of magnitude lower than existing limits. In the near future, the digital radio array LOFAR will be used to achieve an even lower limit.
Key words: astroparticle physics / neutrinos / methods: data analysis / methods: observational / radiation mechanisms: non-thermal
© ESO, 2010
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