8,023 research outputs found
Time Resolved GRB Spectroscopy
We present the main results of a study of time-resolved spectra of 43 intense
GRBs detected by BATSE. We considered the 4-parameter Band model and the
Optically Thin Synchrotron Shock model (OTSSM). We find that the large majority
of time-resolved spectra of GRBs are in remarkable agreement with the OTSSM.
However, about 15 % of initial GRB pulses show an apparent low-energy photon
suppression. This phenomenon indicates that complex radiative conditions
modifying optically thin emission may occur during the initial phases of some
GRBs.Comment: 5 pages, 3 figures, Paper presented at the 5th Huntsville Symposium,
Huntsville (Alabama) Oct. 199
A New Search Paradigm for Correlated Neutrino Emission from Discrete GRBs using Antarctic Cherenkov Telescopes in the Swift Era
We describe the theoretical modeling and analysis techniques associated with
a preliminary search for correlated neutrino emission from GRB980703a, which
triggered the Burst and Transient Source Experiment (BATSE GRB trigger 6891),
using archived data from the Antarctic Muon and Neutrino Detector Array
(AMANDA-B10). Under the assumption of associated hadronic acceleration, the
expected observed neutrino energy flux is directly derived, based upon
confronting the fireball phenomenology with the discrete set of observed
electromagnetic parameters of GRB980703a, gleaned from ground-based and
satellite observations, for four models, corrected for oscillations. Models 1
and 2, based upon spectral analysis featuring a prompt photon energy fit to the
Band function, utilize an observed spectroscopic redshift, for isotropic and
anisotropic emission geometry, respectively. Model 3 is based upon averaged
burst parameters, assuming isotropic emission. Model 4, based upon a Band fit,
features an estimated redshift from the lag-luminosity relation with isotropic
emission. Consistent with our AMANDA-II analysis of GRB030329, which resulted
in a flux upper limit of ~0.150 GeV/cm^2/s for model 1, we find differences in
excess of an order of magnitude in the response of AMANDA-B10, among the
various models for GRB980703a. Implications for future searches in the era of
Swift and IceCube are discussed.Comment: 7 pages, 4 figures, 4 tables, Contributed to the Proceedings of The
16th Annual Astrophysics Conference in Maryland: Gamma Ray Bursts in the
Swift Era. Edited by Stephen S. Holt, Neil Gehrels and John A. Nousek (2006
Loading Bose condensed atoms into the ground state of an optical lattice
We optimize the turning on of a one-dimensional optical potential, V_L(x,t) =
S(t) V_0 cos^2(kx) to obtain the optimal turn-on function S(t) so as to load a
Bose-Einstein condensate into the ground state of the optical lattice of depth
V_0. Specifically, we minimize interband excitations at the end of the turn-on
of the optical potential at the final ramp time t_r, where S(t_r) = 1, given
that S(0) = 0. Detailed numerical calculations confirm that a simple unit cell
model is an excellent approximation when the turn-on time t_r is long compared
with the inverse of the band excitation frequency and short in comparison with
nonlinear time \hbar/\mu where \mu is the chemical potential of the condensate.
We demonstrate using the Gross-Pitaevskii equation with an optimal turn-on
function S(t) that the ground state of the optical lattice can be loaded with
very little excitation even for times t_r on the order of the inverse band
excitation frequency
Partially incoherent gap solitons in Bose-Einstein condensates
We construct families of incoherent matter-wave solitons in a repulsive
degenerate Bose gas trapped in an optical lattice (OL), i.e., gap solitons, and
investigate their stability at zero and finite temperature, using the
Hartree-Fock-Bogoliubov equations. The gap solitons are composed of a coherent
condensate, and normal and anomalous densities of incoherent vapor co-trapped
with the condensate. Both intragap and intergap solitons are constructed, with
chemical potentials of the components falling in one or different bandgaps in
the OL-induced spectrum. Solitons change gradually with temperature. Families
of intragap solitons are completely stable (both in direct simulations, and in
terms of eigenvalues of perturbation modes), while the intergap family may have
a very small unstable eigenvalue (nevertheless, they feature no instability in
direct simulations). Stable higher-order (multi-humped) solitons, and bound
complexes of fundamental solitons are found too.Comment: 8 pages, 9 figures. Physical Review A, in pres
Target Mass Monitoring and Instrumentation in the Daya Bay Antineutrino Detectors
The Daya Bay experiment measures sin^2 2{\theta}_13 using functionally
identical antineutrino detectors located at distances of 300 to 2000 meters
from the Daya Bay nuclear power complex. Each detector consists of three nested
fluid volumes surrounded by photomultiplier tubes. These volumes are coupled to
overflow tanks on top of the detector to allow for thermal expansion of the
liquid. Antineutrinos are detected through the inverse beta decay reaction on
the proton-rich scintillator target. A precise and continuous measurement of
the detector's central target mass is achieved by monitoring the the fluid
level in the overflow tanks with cameras and ultrasonic and capacitive sensors.
In addition, the monitoring system records detector temperature and levelness
at multiple positions. This monitoring information allows the precise
determination of the detectors' effective number of target protons during data
taking. We present the design, calibration, installation and in-situ tests of
the Daya Bay real-time antineutrino detector monitoring sensors and readout
electronics.Comment: 22 pages, 20 figures; accepted by JINST. Changes in v2: minor
revisions to incorporate editorial feedback from JINS
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