9 research outputs found
Cherenkov radio pulses from electromagnetic showers in the time-domain
The electric field of the Cherenkov radio pulse produced by a single charged
particle track in a dielectric medium is derived from first principles. An
algorithm is developed to obtain the pulse in the time domain for numerical
calculations. The algorithm is implemented in a Monte Carlo simulation of
electromagnetic showers in dense media (specifically designed for coherent
radio emission applications) as might be induced by interactions of ultra-high
energy neutrinos. The coherent Cherenkov radio emission produced by such
showers is obtained simultaneously both in the time and frequency domains. A
consistency check performed by Fourier-transforming the pulse in time and
comparing it to the frequency spectrum obtained directly in the simulations
yields, as expected, fully consistent results. The reversal of the time
structure inside the Cherenkov cone and the signs of the corresponding pulses
are addressed in detail. The results, besides testing algorithms used for
reference calculations in the frequency domain, shed new light into the
properties of the radio pulse in the time domain. The shape of the pulse in the
time domain is directly related to the depth development of the excess charge
in the shower and its width to the observation angle with respect to the
Cherenkov direction. This information can be of great practical importance for
interpreting actual data.Comment: 10 pages, 4 figure
Characterization of neutrino signals with radiopulses in dense media through the LPM effect
We discuss the possibilities of detecting radio pulses from high energy
showers in ice, such as those produced by PeV and EeV neutrino interactions. It
is shown that the rich radiation pattern structure in the 100 MHz to few GHz
allows the separation of electromagnetic showers induced by photons or
electrons above 100 PeV from those induced by hadrons. This opens up the
possibility of measuring the energy fraction transmitted to the electron in a
charged current electron neutrino interaction with adequate sampling of the
angular distribution of the signal. The radio technique has the potential to
complement conventional high energy neutrino detectors with flavor information.Comment: 5 pages, 4 ps figures. Submitted to Phys. Rev. Let
Prospects for radio detection of ultra-high energy cosmic rays and neutrinos
The origin and nature of the highest energy cosmic ray events is currently
the subject of intense investigation by giant air shower arrays and fluorescent
detectors. These particles reach energies well beyond what can be achieved in
ground-based particle accelerators and hence they are fundamental probes for
particle physics as well as astrophysics. Because of the scarcity of these
high-energy particles, larger and larger ground-based detectors have been
built. The new generation of digital radio telescopes may play an important
role in this, if properly designed. Radio detection of cosmic ray showers has a
long history but was abandoned in the 1970's. Recent experimental developments
together with sophisticated air shower simulations incorporating radio emission
give a clearer understanding of the relationship between the air shower
parameters and the radio signal, and have led to resurgence in its use.
Observations of air showers by the SKA could, because of its large collecting
area, contribute significantly to measuring the cosmic ray spectrum at the
highest energies. Because of the large surface area of the moon, and the
expected excellent angular resolution of the SKA, using the SKA to detect radio
Cherenkov emission from neutrino-induced cascades in lunar regolith will be
potentially the most important technique for investigating cosmic ray origin at
energies above the photoproduction cut-off. (abridged)Comment: latex, 26 pages, 17 figures, to appear in: "Science with the Square
Kilometer Array," eds. C. Carilli and S. Rawlings, New Astronomy Reviews,
(Elsevier: Amsterdam
Cherenkov radio pulses from EeV neutrino interactions: the LPM effect
We study the implications of the LPM effect for the Cherenkov radiation of
EeV electromagnetic showers in the coherent radiowave regime for ice. We show
that for showers above 100~PeV the electric field scales with shower energy but
has a markedly narrower angular distribution than for lower energy showers. We
give an electric field frequency and angular spectrum parameterization valid
for showers having energy up to the EeV regime and discuss the implications for
neutrino detectors based on arrays of radio antennas. Implications of the LPM
effect for under water neutrino detectors in project are also briefly
addressed.Comment: 15 pages, 2 tables, 3 postscript figure