Constraints on the flux of Ultra-High Energy neutrinos from WSRT observations

TL;DR

This study used the Westerbork Synthesis Radio Telescope to observe the Moon and set new, more stringent limits on ultra-high energy neutrino flux by detecting Askaryan effect signals, improving previous bounds.

Contribution

The paper presents the first limits on UHE neutrino flux obtained with WSRT observations of the Moon, utilizing a novel trigger and filtering system to enhance detection sensitivity.

Findings

Set a new upper limit on UHE neutrino flux, an order of magnitude lower than previous limits.

Developed a pulse detection system with simulated pulse insertion to evaluate detection efficiency.

Demonstrated the feasibility of using radio telescopes for UHE neutrino detection.

Abstract

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. By observing the Moon with the Westerbork Synthesis Radio Telescope array we are able to set a new limit on the UHE neutrino flux. 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. 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.