LUX-ZEPLIN

Abstract:

Most ultra-high energy neutrino experiments using ice as a target medium rely on the Askaryan effect (coherent impulsive radio Cherenkov radiation from the charge asymmetry in an electromagnetic shower). This effect was measured with the Antarctic Impulsive Transient Antenna (ANITA) experiment at the Stanford Linear Accelerator Center (SLAC) in June 2006. The showers were produced by 28.5 GeV electrons with a number density of 109 electrons per bunch impacting a 7.5 metric ton ice target (roughly 12.5 radiation lengths). In this paper we present the measured angular and frequency dependence of the radiation and compare the results with the predicted response.

Abstract:

Radiowave detection of the Cherenkov radiation produced by neutrino-ice collisions requires an understanding of the radiofrequency (RF) response of cold polar ice. We herein report on a series of radioglaciological measurements performed approximately 10 km north of Taylor Dome Station, Antarctica from Dec. 6, 2006 - Dec. 16, 2006. Using RF signals broadcast from a dual-polarization horn antenna on the surface transmitting signals which reflect off the underlying bed and back up to a dual polarization surface horn receiver, we have made time-domain estimates of both the real (index-of-refraction "n") and imaginary (attenuation length "Latten") components of the complex ice dielectric constant (ε = ε′ +iε′ ′). We have also measured the uniformity of ice response along two orthogonal axes in the horizontal plane. We observe an apparent wavespeed asymmetry of order 0.1%, between two orthogonal linear polarizations projected into the horizontal plane, consistent with some previous measurements, but somewhat lower than others.

Abstract:

The ANtarctic Impulse Transient Antenna (ANITA) is the first long-duration balloon experiment designed to search and measure the flux of Greisen- Zapsepin-Kuzmin (GZK) neutrinos. We present new limits on neutrinos fluxes of astronomical origin from data collected with the successful launch of a 2- antenna prototype instrument, called ANITA-lite, that circled the Antarctic continent for 18.4 days in January 2004. We performed a search for Ultra- High-Energy (UHE) neutrinos with energies above 3 x 1018 eV. No excess events above the background expectation were observed and a neutrino flux following E-2 spectrum for all neutrino flavors, is limited to Ev-2F < 1.6 × 10-6 GeV cm-2 s-1 sr-1 for 1018.5 eV < Ev < 1023.5 eV at 90% confidence level. The launch of ANITA is scheduled for December 2006. Looking beyond ANITA, we describe a new idea, called ARIANNA (Antarctic Ross Iceshelf ANtenna Neutrino Array), to increase the sensitivity for GZK neutrinos by one order of magnitude better than ANITA. Copyright © 2007 by World Scientific Publishing Co. Pvt. Ltd.

Abstract:

The temperature dependence of the decay time and scintillation light yield of pure CaF2 crystal was measured over the temperature range 8-305 K using the multiphoton coincidence counting technique. Pure CaF2 exhibits emission of triplet self-trapped excitons at 280 nm with a slow decay, the time constant of which changes significantly with temperature. The main decay time constant increases by three orders of magnitude when cooled, from 0.96±0.06 μs at 295 K to 930±40 μs at 8 K. The results obtained demonstrate that the scintillation light yield of pure CaF2 increases with decreasing temperature down to 20 K below which it is roughly constant. At low temperatures the light yield of CaF2 is estimated to be 60% relative to that of pure CaWO4. It is concluded that undoped calcium fluoride is a very attractive target material for experimental searches for rare events based on the detection of phonon and scintillation signals. © 2006 Elsevier B.V. All rights reserved.