70 research outputs found
Signal Characteristics from Electromagnetic Cascades in Ice
We investigate the development of electromagnetic cascades in ice using a
GEANT Monte Carlo simulation. We examine the Cherenkov pulse that is generated
by the charge excess that develops and propagates with the shower. This study
is important for the RICE experiment at the South Pole, as well as any test
beam experiment which seeks to measure coherent Cherenkov radiation from an
electromagnetic shower.Comment: 8 pages, 6 figure
Numerical Aspects of Bubble Nucleation
Bubble nucleation has been studied on lattices using phenomenological
Langevin equations. Recently there have been theoretical motivations for using
these equations. These studies also conclude that the simple Langevin
description requires some modification. We study bubble nucleation on a lattice
and determine effects of the modified Langevin equations.Comment: Talk given at DPF2000, Columbus, Ohio; 4 pages, 4 figure
Addendum to "Coherent radio pulses from GEANT generated electromagnetic showers in ice"
We reevaluate our published calculations of electromagnetic showers generated
by GEANT 3.21 and the radio frequency pulses they produce in ice. We are
prompted by a recent report showing that GEANT 3.21-modeled showers are
sensitive to internal settings in the electron tracking subroutine. We report
the shower and pulse characteristics obtained with different settings of GEANT
3.21 and with GEANT 4. The default setting of electron tracking in GEANT 3.21
we used in previous work speeds up the shower simulation at the cost of
information near the end of the tracks. We find that settings tracking electron
and positron to lower energy yield a more accurate calculation, a more intense
shower, and proportionately stronger radio pulses at low frequencies. At high
frequencies the relation between shower tracking algorithm and pulse spectrum
is more complex. We obtain radial distributions of shower particles and phase
distributions of pulses from 100 GeV showers that are consistent with our
published results.Comment: 4 pages, 3 figure
Coherent Radio Pulses From GEANT Generated Electromagnetic Showers In Ice
Radio Cherenkov radiation is arguably the most efficient mechanism for
detecting showers from ultra-high energy particles of 1 PeV and above. Showers
occuring in Antarctic ice should be detectable at distances up to 1 km. We
report on electromagnetic shower development in ice using a GEANT Monte Carlo
simulation. We have studied energy deposition by shower particles and
determined shower parameters for several different media, finding agreement
with published results where available. We also report on radio pulse emission
from the charged particles in the shower, focusing on coherent emission at the
Cherenkov angle. Previous work has focused on frequencies in the 100 MHz to 1
GHz range. Surprisingly, we find that the coherence regime extends up to tens
of Ghz. This may have substantial impact on future radio-based neutrino
detection experiments as well as any test beam experiment which seeks to
measure coherent Cherenkov radiation from an electromagnetic shower. Our study
is particularly important for the RICE experiment at the South Pole.Comment: 44 pages, 29 figures. Minor changes made, reference added, accepted
for publication in Phys. Rev.
Additive and Multiplicative Noise Driven Systems in 1+1 Dimensions: Waiting Time Extraction of Nucleation Rates
We study the rate of true vacuum bubble nucleation numerically for a phi^4
field system coupled to a source of thermal noise. We compare in detail the
cases of additive and multiplicative noise. We pay special attention to the
choice of initial field configuration, showing the advantages of a version of
the quenching technique. We advocate a new method of extracting the nucleation
time scale that employs the full distribution of nucleation times. Large data
samples are needed to study the initial state configuration choice and to
extract nucleation times to good precision. The 1+1 dimensional models afford
large statistics samples in reasonable running times. We find that for both
additive and multiplicative models, nucleation time distributions are well fit
by a waiting time, or gamma, distribution for all parameters studied. The
nucleation rates are a factor three or more slower for the multiplicative
compared to the additive models with the same dimensionless parameter choices.
Both cases lead to high confidence level linear fits of ln(nucleation time) vs.
1/T plots, in agreement with semiclassical nucleation rate predictions.Comment: 38 pages, 20 figures, 6 table
Measuring the Neutrino Cross Section Using 8 years of Upgoing Muon Neutrinos Observed with IceCube
The IceCube Neutrino Observatory detects neutrinos at energies orders of magnitude higher than those available to current accelerators. Above 40 TeV, neutrinos traveling through the Earth will be absorbed as they interact via charged current interactions with nuclei, creating a deficit of Earth-crossing neutrinos detected at IceCube. The previous published results showed the cross section to be consistent with Standard Model predictions for 1 year of IceCube data. We present a new analysis that uses 8 years of IceCube data to fit the ν absorption in the Earth, with statistics an order of magnitude better than previous analyses, and with an improved treatment of systematic uncertainties. It will measure the cross section in three energy bins that span the range 1 TeV to 100 PeV. We will present Monte Carlo studies that demonstrate its sensitivity
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