Self-triggered radio detection and identification of cosmic air showers with the OVRO-LWA

Abstract

A successful ground array Radio Frequency (RF)-only self-trigger on 10 highenergy cosmic ray events is demonstrated with 256 dual-polarization antennas of the Owens Valley Radio Observatory Long Wavelength Array (OVRO-LWA).This RF-only capability is predicated on novel techniques for Radio Frequency Interference (RFI) identification and mitigation with an analysis efficiency of 45% for shower-driven events with a Signal-to-noise ratio 5 against the galactic background noise power of individual antennas. This technique enables more efficient detection of cosmic rays over a wider range of zenith angles than possible via triggers from in-situ particle detectors and can be easily adapted by neutrino experiments relying on RF-only detection. This paper discusses the system design, RFI characterization and mitigation techniques, and initial results from 10 cosmic ray events identified within a 40-hour observing window. A design for a future optimized commensal cosmic-ray detector for the OVRO-LWA is presented, as well as recommendations for developing a similar capability for other experiments -these designs either reduce data-rate or increase sensitivity by an order of magnitude for many configurations of radio instruments.

Prospects for high-elevation radio detection of 0>10 PeV tau neutrinos

“…The mountaintop radio detector design assumes that a site is radio quiet enough to trigger efficiently on signals 5σ above the thermal noise background over a 120 degree field of view in azimuth. This technological capability has yet to be demonstrated, but analyses from the TREND [31] and OVRO-LWA [29] experiments suggest that radio-only triggering may be possible by rejecting triggers arriving from certain directions at the trigger level. A prototype beamformer array of four 30-80 MHz antennas has been deployed at the White Mountain Research Station in Bishop CA.…”

“…Arrays of radio antennas can be used in different configurations at a given station to observe radio signals from particle showers depending on the goals of the detector. Some radio experiments [22,29,33] use a large number of antennas packed in a small number of stations to observe the footprint of the air shower on the ground. Other experiments [17,18,34], use a small number of antennas per station to search for emission from the whole shower generated by a neutrino interaction.…”

Cosmic Ray Detection at the Murchison Radio-astronomy Observatory – a pathfinder for SKA-Low

“…MWA cosmic ray detection Alexander Williamson Importantly, we have encountered a very low RFI rate -of order two events/minute only, when excluding two periods (less than 10% of the data) with unusually high rates. This is many orders of magnitude lower than encountered with similar experiments at OVRO-LWA [4] and LOFAR [2], and due to the remoteness of, and strict RFI controls within, the MRO.…”

“…In particular, LOFAR [2] has pioneered the use of a low-frequency radio telescope built primarily for imaging observations for cosmic ray detection, where the high antenna density yields a high degree of precision on individual events. More recently, OVRO-LWA have detected a sample of cosmic rays using a specialist observation mode [4]. In the long term, the High Energy Cosmic Particles focus group of the Square Kilometre Array (SKA) propose to use the SKA's low-frequency antenna for even high precision measurements [5].…”

Modeling and Validating RF-Only Interferometric Triggering with Cosmic Rays for BEACON

“…To estimate the acceptance of BEACON to cosmic rays, and from there the detection rate, a Monte-Carlo simulation based on that used by the OVRO-LWA experiment [10] was developed named the Cosmic Ray Simulation for a Beamforming Elevated Array, or Cranberry. In this paper, we will first discuss how Cranberry works, then we will present the estimated acceptance and cosmic ray event rate for the BEACON prototype, and lastly we will discuss future plans for Cranberry and BEACON.…”