Constraints on ultra-high-energy neutrino flux from radio observations of the Moon

Abstract

Abstract. The NuMoon project aims to study ultra-highenergy neutrinos and cosmic rays by using radio telescopes to search for short pulses from the Moon. These pulses are created when a neutrino or cosmic ray impinges on the Moon and interacts below the lunar surface. Part of the energy is converted into a hadronic shower, which emits radio emission in a process known as the Askaryan effect. In the first phase of the NuMoon project, 46 hrs of data were collected with the Westerbork Synthesis Radio Telescope in a low frequency band: 40 − 80 MHz. This resulted in an upper limit on the neutrino flux above 10 22 eV which is an order of magnitude lower than previous limits. Additionally, an upper limit has been set on the ultra-high-energy cosmic-ray flux. The second phase of NuMoon will consist of observations with LOFAR.

High-energy and ultra-high-energy neutrinos: A Snowmass white paper

“…The technical requirements on radio telescopes are access to full time-domain voltages of the receiver and multiple beams on-and off-Moon, making not all telescopes suitable for these studies. Past observations have been performed most notably by the Parkes [633] and Westerbork telescopes [634] and the EVLA [635], with past and on-going work being performed with LOFAR [636,637]. The next step in sensitivity will be obtainable with the Square-Kilometre Array (SKA) [632,[638][639][640].…”

The effects of surface roughness on lunar Askaryan pulses

“…All current [1,2] and future [3,4,5] experiments aiming to use the upper lunar surface layers as a medium for ultra-high-energy (UHE) particle detection via the Askaryan effect involve observing the Moon from large distances, either via satellite, or from the Earth itself. While Askaryan pulses are characterised by their broadband coherence, linear polarisation, and very short duration, any pulses of radiation which might be detected by these experiments must first pass through the rough lunar surface.…”

“…While Askaryan pulses are characterised by their broadband coherence, linear polarisation, and very short duration, any pulses of radiation which might be detected by these experiments must first pass through the rough lunar surface. Current models of the transmission process, as used in simulations to estimate experimental sensitivity [2,6,7,8,9], only deal with the large-scale effects of surface roughness in refracting a pulse. It has also recently been shown that the lunar Askaryan technique will be sensitive to cosmic-ray interactions [10,11], and consequently these particles have become the target of proposed experiments with the SKA [3] -yet previous estimates of lunar surface roughness effects have only modelled neutrino interactions [12,7].…”