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Dept. Physics and Astronomy - U. Iowa
Expanded Very Large Array (EVLA)
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News / Updates

09/13/2009
First Phase-B Observation. Setup images coming soon!

08/22/2009
The VLA has informed us that Phase-B is green-lighted and set to start Sept. 15th.

06/15/2009
Doug Karkow ICRU Feature
ICRUFeatureKarkowSP09

04/22/2009
Analytic Aperture paper submitted to astro-ph.
0904.3389v2

Contacts

Ted Jaeger
University of Iowa, (319) 335-1755
theodore-jaeger@uiowa.edu

Dr. Robert Mutel
University of Iowa, (319) 335-1950
robert-mutel@uiowa.edu

Introduction to RESUN

Ultra-high energy (UHE: E > 1019 eV) neutrino astronomy is a new window to high-energy astrophysical processes.  Potential UHE neutrino sources include Active Galactic Nuclei (AGN) primaries, GZK-induced showers from UHE cosmic rays, Z-bursts from massive primordial remnant particles, and topological defects.

For distant ( > 50 Mpc, 1 Mpc = 3 x 1022 m) sources, neutrinos are the only way to probe physical processes at UHE energies.

This is because cosmic ray primaries interact strongly with Cosmic Microwave Background photons.  The past 20 years have seen numerous experiments aimed at observing these cosmic messengers, however, no attempts have yielded a detection.

Interaction Sketch

Sketch of UHE Neutrino - Lunar Interaction.  Note that only "glancing angle" impacts create observable Cerenkov emission. Details of the interaction and properties of the radio burst are given on the UHE Interaction page.

Project RESUN (Radio EVLA Search for UHE Neutrinos) utilizes multiple antennas in the Expanded Very Large Array (EVLA) to search the lunar limb for nanosecond-duration Cerenkov radio bursts at 1.4 GHz.  These bursts are created when (primarily cosmogenic) UHE neutrinos annihilate in the lunar regolith, producing a particle shower which in turn produces charge currents and consequent Cerenkov radio emission.  The EVLA is currently the best ground-based radio array in the world to search for these bursts in this energy range until the completion of the SKA.  The RESUN search will either make the first UHE neutrino detections, or will provide a new lower limit to neutrino flux in the important energy range just above the GZK limit (1019.5 eV), approximately one order of magnitude lower than previous searches.

RESUN consists of two phases.

Phase B Beam Placement

Proposed Phase-B beam placement.  At 1.45 GHz, the beam size is ~ the same as the lunar apparent size (30 arcmin).  Here, 3 sub-arrays of 4 EVLA antennas are used to monitor the entire lunar limb for ns bursts of emission. 

Phase-A: 45 hrs, completed in March 2008, utilized one sub-array of 4 EVLA antennas. This phase had two goals:

(a) provide proof-of-concept demonstration  of the hardware and software schemes needed for Phase-B

(b) verify the lower limit to isotropic UHE neutrino flux determined from previous experiments. Although no detections were made, we verified the most sensitive previously published lower flux limit for isotropic neutrinos in the energy range 1020.5-21.5 eV.

Phase-B: 200 hrs, proposed June 2009, will utilize three 4-antenna sub-arrays with both R and L polarization channels. The combination of full limb coverage, dual polarization, and 5x more observing time will probe neutrino fluxes more than one order of magnitude lower than has ever been observed.