Optimal radio window for the detection of Ultra-High Energy cosmic rays and neutrinos off the moon

Abstract

When high-energy cosmic rays impinge on a dense dielectric medium, radio waves are produced through the Askaryan effect. We show that at wavelengths comparable to the length of the shower produced by an Ultra-High Energy cosmic ray or neutrino, radio signals are an extremely efficient way to detect these particles. Through an example it is shown that this new approach offers, for the first time, the realistic possibility of measuring UHE neutrino fluxes below the Waxman-Bahcall limit. It is shown that in only one month of observing with the upcoming LOFAR radio telescope, cosmic-ray events can be measured beyond the GZK-limit, at a sensitivity level of two orders of magnitude below the extrapolated values.

Prospects for the Giant Metrewave Radio Telescope to observe radio waves from ultra high energy particles interacting with the Moon

“…6 respectively. We also show the results of carrying through our calculations for the LOFAR parameters given in [17]. When compared to the LOFAR Monte Carlo simulation results, the two methods of calculation agree within a factor two over the full energy range.…”

“…This figure contains, in addition to the GMRT results for ν = 150 MHz with two different observation times, the already existing limits from RICE [25], GLUE [12], FORTE [26] and ANITA-lite [7]. Also we have indicated the prospective future limits that has been calculated for ANITA [7], LOFAR [17] or LORD [18].…”

“…High energy charged particles from UHE cosmic ray (CR) or UHE neutrino interactions in the lunar regolith will initiate a cascading shower with total energy E s and typical length scale [17] L(E s ) = 12.7 + 2 3 log 10 E s 10 20 eV (1) in units of radiation length. For the lunar regolith with radiation length X 0 = 22.1 g/cm 2…”

“…The intensity of radio waves on Earth from a shower in the lunar regolith with energy E s emittingČerenkov emission has been parameterized from simulations [17,21]. At an angle θ to the shower axis, for radiation frequency ν and bandwidth ∆ν, it is given by (4) where R is the distance between the emission point on the Moon's surface to the telescope and ν 0 = 2.5 GHz.…”

“…For future experiments with increased sensitivity there are proposals [15,16,17] to study this effect with upcoming radio telescopes like the Low Frequency Array (LOFAR) and the Square Kilometer Array (SKA), or to use lunar orbiting artificial satellites carrying one or more radio antennas [18,19].…”