1,430 research outputs found
Spin dependent structure function g_1 at low x and low Q^2
Theoretical description of the spin dependent structure function g_1(x,Q^2)
in the region of low values of x and Q^2 is presented. It contains the Vector
Meson Dominance contribution and the QCD improved parton model suitably
extended to the low Q^2 domain. Theoretical predictions are compared with the
recent experimental data in the low x, low Q^2 region
Performance of the ARIANNA Hexagonal Radio Array
Installation of the ARIANNA Hexagonal Radio Array (HRA) on the Ross Ice Shelf
of Antarctica has been completed. This detector serves as a pilot program to
the ARIANNA neutrino telescope, which aims to measure the diffuse flux of very
high energy neutrinos by observing the radio pulse generated by
neutrino-induced charged particle showers in the ice. All HRA stations ran
reliably and took data during the entire 2014-2015 austral summer season. A new
radio signal direction reconstruction procedure is described, and is observed
to have a resolution better than a degree. The reconstruction is used in a
preliminary search for potential neutrino candidate events in the data from one
of the newly installed detector stations. Three cuts are used to separate radio
backgrounds from neutrino signals. The cuts are found to filter out all data
recorded by the station during the season while preserving 85.4% of simulated
neutrino events that trigger the station. This efficiency is similar to that
found in analyses of previous HRA data taking seasons.Comment: Proceedings from the 34th ICRC2015, http://icrc2015.nl/ . 8 pages, 6
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A First Search for Cosmogenic Neutrinos with the ARIANNA Hexagonal Radio Array
The ARIANNA experiment seeks to observe the diffuse flux of neutrinos in the
10^8 - 10^10 GeV energy range using a grid of radio detectors at the surface of
the Ross Ice Shelf of Antarctica. The detector measures the coherent Cherenkov
radiation produced at radio frequencies, from about 100 MHz to 1 GHz, by
charged particle showers generated by neutrino interactions in the ice. The
ARIANNA Hexagonal Radio Array (HRA) is being constructed as a prototype for the
full array. During the 2013-14 austral summer, three HRA stations collected
radio data which was wirelessly transmitted off site in nearly real-time. The
performance of these stations is described and a simple analysis to search for
neutrino signals is presented. The analysis employs a set of three cuts that
reject background triggers while preserving 90% of simulated cosmogenic
neutrino triggers. No neutrino candidates are found in the data and a
model-independent 90% confidence level Neyman upper limit is placed on the all
flavor neutrino+antineutrino flux in a sliding decade-wide energy bin. The
limit reaches a minimum of 1.9x10^-23 GeV^-1 cm^-2 s^-1 sr^-1 in the 10^8.5 -
10^9.5 GeV energy bin. Simulations of the performance of the full detector are
also described. The sensitivity of the full ARIANNA experiment is presented and
compared with current neutrino flux models.Comment: 22 pages, 22 figures. Published in Astroparticle Physic
Livetime and sensitivity of the ARIANNA Hexagonal Radio Array
The ARIANNA collaboration completed the installation of the hexagonal radio
array (HRA) in December 2014, serving as a pilot program for a planned high
energy neutrino telescope located about 110 km south of McMurdo Station on the
Ross Ice Shelf near the coast of Antarctica. The goal of ARIANNA is to measure
both diffuse and point fluxes of astrophysical neutrinos at energies in excess
of 1016 eV. Upgraded hardware has been installed during the 2014 deployment
season and stations show a livetime of better than 90% between commissioning
and austral sunset. Though designed to observe radio pulses from neutrino
interactions originating within the ice below each detector, one station was
modified to study the low-frequency environment and signals from above. We
provide evidence that the HRA observed both continuous emission from the Galaxy
and a transient solar burst. Preliminary work on modeling the (weak) Galactic
signal confirm the absolute sensitivity of the HRA detector system.Comment: Proceedings from the 34th ICRC2015, http://icrc2015.nl/, 8 pages, 6
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