Observations of the Askaryan Effect in Ice Page: 1 of 4
4 pagesView a full description of this article.
Extracted Text
The following text was automatically extracted from the image on this page using optical character recognition software:
SLAC-PUB-12286
hep-ex/0611008
January 2007Observations of the Askaryan Effect in Ice
The ANITA collaboration: P. W. Gorham1, S. W. Barwick2, J. J. Beatty3, D. Z. Besson4, W. R. Binns5, C. Chen6, P. Chen6,
J. M. Clem7, A. Connolly8, P. E Dowkontt5, M. A. DuVernois9, R. C. Field6, D. Goldstein2, A. Goodhue8 C. Hast6,
C. L. Hebert1, S. Hoover8, M. H. Israels, J. Kowalski,1 J. G. Learned, K. M. Liewero, J. T. Link', E. Lusczek9,
S. Matsuno1, B. Mercurio3, C. Mikil, P. Miocinovi1, J. Nam2, C. J. Naudet10, J. Ng6, R. Nichol3, K. Palladino3,
K. Reil6, A. Romero-Wolf' M. Rosen1, L. Ruckman, D. Saltzberg8, D. Seckel7, G. S. Varner1, D. Walz6, E Wu21
1 Dept. of Physics and Astronomy, Univ. of Hawaii, Manoa,
HI 96822. 2Univ. of California, Irvine CA 92697. 3Dept. of Physics,
Ohio State Univ., Columbus, OH 43210. 4Dept. of Physics and Astronomy,
Univ. of Kansas, Lawrence, KS 66045. 5Dept. of Physics,
Washington Univ. in St. Louis, MO 63130. 6Stanford Linear Accelerator Center
Menlo Park, CA, 94025. 7University of Delaware, Newark,
DE 19716 8Dept. of Physics and Astronomy, Univ. of California, Los Angeles,
CA 90095. 9School of Physics and Astronomy, Univ. of Minnesota,
Minneapolis, MN 55455. 10Jet Propulsion Laboratory, Pasadena,
CA 91109. "Currently at NASA Goddard Space Flight Center Greenbelt, MD, 20771.
We report on the first observations of the Askaryan effect in ice: coherent impulsive radio Cherenkov radiation
from the charge asymmetry in an electromagnetic (EM) shower. Such radiation has been observed in silica
sand and rock salt, but this is the first direct observation from an EM shower in ice. These measurements
are important since the majority of experiments to date that rely on the effect for ultra-high energy neutrino
detection are being performed using ice as the target medium. As part of the complete validation process for
the Antarctic Impulsive Transient Antenna (ANITA) experiment, we performed an experiment at the Stanford
Linear Accelerator Center (SLAC) in June 2006 using a 7.5 metric ton ice target, yielding results fully consistent
with theoretical expectations.Very large scale optical Cherenkov detectors such as the
Antarctic Muon and Neutrino Detector Array (AMANDA)
and its successor IceCube have demonstrated the excellent
utility of Cherenkov radiation in detection of neutrino inter-
actions at >TeV energies [1, 2] with ice as a target medium.
However, at neutrino energies above 100 PeV, the cubic-km
scale of such detectors is inadequate to detect more than a
handful of events from the predicted cosmogenic neutrino
fluxes [3] which represent the most compelling models at
these energies. The relevant detector volume for convinc-
ing detection and characterization of these neutrinos is in the
range of hundreds to thousands of cubic km of water equiva-
lent mass, and the economic constraints of scaling up the opti-
cal Cherenkov technique almost certainly preclude extending
it much beyond the size of the current IceCube detector, which
will be completed early in the next decade.
Given the need for an alternative technique with a more
tractable economy of scale to reach into the EeV (=1000
PeV) energy regime, a new method which we denote the ra-
dio Cherenkov technique, has emerged within the last decade.
This method relies on properties of electromagnetic cas-
cades in a dielectric medium. It was first hypothesized by
Askaryan [4] and confirmed in 2001 at SLAC [5]. High en-
ergy processes such as Compton, Bhabha, and Moller scatter-
ing, along with positron annihilation rapidly lead to a ~ 20%
negative charge asymmetry in the electron-photon part of a
cascade. In dense media the shower charge bunch is com-
pact, largely contained within a several cm radius. At wave-
lengths of 10 cm or more, much larger than the characteristic
shower bunch size, the relativistic shower bunch appears asa single charge moving through the dielectric over a distance
of several meters or more. As an example, a typical shower
with mean Bjorken inelasticity (y) 0.2, initiated by a Ev
100 PeV neutrino will create a total number of charged parti-
cles at shower maximum of order ne+ +n = (y)Ev/1 GeV ~
2 x 107. The net charge is thus ne+ ne_ - 4 x 106 e. Since
the radiated power for Cherenkov emission grows quadrati-
cally with the charge of the emitter, the coherent power in the
cm-to-m wavelength regime is ~ 1013 times greater than that
emitted incoherently, far exceeding any other secondary emis-
sion in optical or longer-wave bands.
Prior to the first laboratory tests of the Askaryan effect in
1999-2000 [5, 6], and subsequent measurements in 2002 [12],
it had been largely ignored since initial putative measurements
of the effect in air showers were found instead to be due to
a process related to synchrotron emission [13, 14]. In the
mid-to-late 1980's, proposals to observe Askaryan impulses
from neutrino interactions in Antarctic ice [15, 16, 17] and the
Lunar regolith [18] created a renewed interest in Askaryan's
work. In the early 1990's, the first comprehensive effort to
combine EM shower simulations in ice with electrodynamics
resulted in strong support for the validity of the methods [10],
and in the later 1990's the Radio Ice Cherenkov Experiment
(RICE) [19], and Goldstone Lunar Ultra-high energy neutrino
Experiment (GLUE) [20] began operation of experiments de-
signed to exploit the effect. More recently, the Fast On-orbit
Recorder of Transient Events (FORTE) [21] satellite and the
ANITA [8] experiment have extended the method to synop-
tic spacecraft or balloon-payload observations of ultra-large
volumes of the Greenland or Antarctic ice sheet.Submitted to Physical Review Letters
Work supported in part by the US Department of Energy contract DE-AC02-76SF00515
Upcoming Pages
Here’s what’s next.
Search Inside
This article can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Article.
Gorham, P. W. Observations of the Askaryan Effect in Ice, article, January 16, 2007; [Menlo Park, California]. (https://digital.library.unt.edu/ark:/67531/metadc885053/m1/1/: accessed July 17, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.