The Antarctic Ross Ice-shelf Antenna Neutrino Array (ARIANNA) experiment exploits serendipitous properties of the Ross Ice Shelf in Western Antarctica. The ice shelf forms the fiducial volume of an ultra-high energy (UHE) neutrino detector capable of observing cosmogenic neutrinos with energies in excess of 1017 eV. The clarity of the shelf ice and the reflectivity of the ocean-ice interface enhance the detection of radio-frequency (RF) electromagnetic pulses created by neutrino interactions via the Askaryan effect. An array of autonomous electronics stations outfitted with radio antennas listen for these pulses.
A prototype station was designed in 2009, using sustainable power and RF trigger and digitization electronics. It was deployed in Moore's Bay in December 2009 during the Austral summer, and additional data was collected in two subsequent seasons after the system rebooted automatically during Austral spring. This data located and helped to remove local anthropogenic noise. A total of 90.4 days of live-time was achieved, with thermal noise as the single background. Additionally, data characterizing the environment of Moore's Bay was collected and used in the development of future power systems and RF electronics.
The depth and dielectric properties of the ice beneath the detectors were calculated using data taken during the expeditions. The linear fit to the frequency-dependent, temperature-averaged attenuation length of radio waves is ⟨L⟩ = (500 ± 30 − (0.18 ± 0.05)ν[MHz]) m, and the reflection coefficient at the oceanic interface is 0.70 ≤ [special characters omitted] ≤ 1.0 at 68% C.L. The depth of the shelf is 576 ± 2 m. The possibility of surface effects capable of boosting detector sensitivity was also revealed in these studies.
Finally, the RF data collected by the first ARIANNA station was analyzed and compared to Monte Carlo simulations modeling the detector response. These studies have produced the first upper limit on the differential UHE neutrino flux from ARIANNA, and the integral flux limit assuming a E −2 spectrum is E2&phis; < 10−5 GeV cm−2 s−1 sr−1. These limits demonstrate that the completed version of ARIANNA will have the capability to observe UHE cosmogenic neutrinos.
|Advisor:||Barwick, Steven W.|
|Commitee:||Kleinfelder, Stuart, Yodh, Gaurang|
|School:||University of California, Irvine|
|Department:||Physics - Ph.D.|
|School Location:||United States -- California|
|Source:||DAI-B 74/07(E), Dissertation Abstracts International|
|Keywords:||Antarctica, Askaryan, Cosmic ray, High-energy, Neutrino|
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