RadNu
The RadNu project is separated into its main focus, providing the proof-of-principle of the Radar detection method to probe high-energy cosmic-neutrino-induced particle cascades in ice, and its secondary focus, understanding and detection of the direct radio emission induced by a high-energy cosmic-ray or neutrino induced particle cascade.
Radar detection of high-energy particle cascades and the formation of the Radar Echo Telescope (RET) collaboration:
With the T-576 beam-test experiment performed at the Stanford Linear Accelerator Center, we showed, for the first time in history, a radar reflection from a high-energy particle cascade [1]. This major breakthrough provided the proof-of-principle for the radar method to probe high-energy particle cascades, after which the Radar Echo Telescope (RET) collaboration was formed. The collaboration is led by K.D. de Vries and S. Prohira, and consists of members from 9 Universities located in Europe, the U.S. and Taiwan. Webpage: www.radarechotelescope.org.
We subsequently constructed the RET-CR experiment to show the in-nature proof-of-principle of the radar method to probe high-energy particle cascades. The RET-CR cosmic-ray surface detector provides an external trigger for our in-ice radar detector that probes the in-ice continuation of cosmic-ray induced particle cascades. To model this process, a detailed simulation framework has been developed. This framework is used to estimate the expected event rate and to optimize the RET-CR detector layout [2]. The RET-CR detector was successfully installed in May 2023 at Summit Station, Greenland, and operated for several weeks [3]. The detector was updated, and a second run successfully took place from May-Aug 2024. Data analysis is currently ongoing and results will be presented at the 2025 ICRC conference.
Along with these experimental developments, a macroscopic radar reflection model, MARES, was developed [4]. This allowed us to perform signal property studies, and obtain the very promising sensitivities for the future RET-N detector, as shown at ICRC2021 [5].
Direct radio emission from high-energy particle cascades, a (background) signal:
The cosmic-ray or neutrino-induced particle cascade will also emit direct radio emission while propagating in air or through the ice. Within the RadNu project, a complete simulation framework is developed to describe the emission from a cosmic-ray particle cascade moving from air into a high-altitude ice-layer [6], as they pose a possible background/calibration-signal that can be observed by in-ice neutrino radio and radar detectors. This effort showed the direct signal should be detectable and led to signal searches for this process that are currently performed within the ARA, RNO-G and RET collaborations.
Radio signal propagation:
One of the major uncertainties in our radar and radio signal predictions is the propagation of radio-waves in the polar ice. Due to its non-uniform density profile, radio waves will be bent, refracted or reflected. Investigating these non-linear propagation modes lead to the application of so-called parabolic equation (PE) solvers to this problem. In [7,8], we indeed show that standard ray-propagators are insufficient to provide a full description of the expected and observed radio emission.
References:
[1] Observation of Radar Echoes from High-Energy Particle Cascades, S. Prohira, K. D. de Vries, et al., Physical Review Letters, 124(9), 091101 (2020), DOI: 10.1103/physrevlett.124.091101
[2] The Radar Echo Telescope for Cosmic Rays: Pathfinder experiment for a next-generation neutrino observatory, S. Prohira, K. D. de Vries, et. al., Phys.Rev.D 104, 10, 102006 (2021), DOI: 10.1103/physrevd.104.102006
[3] The Radar Echo Telescope for Cosmic Rays, Rose S Stanley for the Radar Echo Telescope collaboration, PoS(ICRC2023), 2023, 474, DOI: 10.22323/1.444.0474
[4] Macroscopic approach to the radar echo scatter from high-energy particle cascades, E. Huesca Santiago, K. D. de Vries, et al. (Radar Echo Telescope collaboration), Phys. Rev. D, 109, 083012 (2024), DOI: 10.1103/physrevd.109.083012
[5] The Radar Echo Telescope for Neutrinos (RET-N), K.D. de Vries for the Radar Echo Telescope collaboration, PoS(ICRC2021), 2021, 1195, DOI: 10.22323/1.395.1195
[6] Simulation of radio signals from cosmic-ray cascades in air and ice as observed by in-ice Askaryan radio detectors, S. De Kockere, D. Van Den Broeck, U.A. Latif, K.D. de Vries, N. van Eijndhoven, T. Huege, S. Buitink, Phy. Rev. D, 10, 2024, 023010, DOI: 10.1103/physrevd.110.023010
[7] Modeling in-ice radio propagation with parabolic equation methods, S. Prohira, et al. (Radar Echo Telescope collaboration), Phys. Rev. D, 103/10, 2021, 103007, DOI: 10.1103/physrevd.103.103007
[8] Validation of straight-line signal propagation for radio signals of very inclined cosmic ray air showers, D. Van den Broeck, U.A. Latif, S. Buitink, K.D. de Vries, T. Huege,Phys. Rev. D, 111, 063062 (2025), DOI:
https://doi.org/10.1103/PhysRevD.111.063062(opens in new window)
