7,015 research outputs found
Optimization of light collection from crystal scintillators for cryogenic experiments
High light collection efficiency is an important requirement in any
application of scintillation detectors. The purpose of this study is to
investigate the possibility for improving this parameter in cryogenic
scintillation bolometers, which can be considered as a promising detectors in
experiments investigating neutrinoless double beta decay and dark matter.
Energy resolutions and relative pulse amplitudes of scintillation detectors
using ZnWO4 scintillation crystals of different shapes (cylinder 20 mm in
dimater by 20 mm and hexagonal prism with diagonal 20 mm and height 20 mm),
reflector materials and shapes, optical contact and surface properties
(polished and diffused) were measured at room temperature. Propagation of
optical photons in these experimental conditions was simulated using Geant4 and
ZEMAX codes. The results of the simulations are found to be in good agreement
with each other and with direct measurements of the crystals. This could be
applied to optimize the geometry of scintillation detectors used in the
cryogenic experiments.Comment: 12 pages, 8 figures, 1 Tabl
Impact of geometry on light collection efficiency of scintillation detectors for cryogenic rare event searches
Simulations of photon propagation in scintillation detectors were performed
with the aim to find the optimal scintillator geometry, surface treatment, and
shape of external reflector in order to achieve maximum light collection
efficiency for detector configurations that avoid direct optical coupling, a
situation that is commonly found in cryogenic scintillating bolometers in
experimental searches for double beta decay and dark matter. To evaluate the
light collection efficiency of various geometrical configurations we used the
ZEMAX ray-tracing software. It was found that scintillators in the shape of a
triangular prism with an external mirror shaped as truncated cone gives the
highest light collection efficiency. The results of the simulations were
confirmed by carrying out measurements of the light collection efficiencies of
CaWO4 crystal scintillators. A comparison of simulated and measured values of
light output shows good agreemen
Dynamics of open quantum systems initially entangled with environment: Beyond the Kraus representation
We present a general analysis of the role of initial correlations between the
open system and an environment on quantum dynamics of the open system.Comment: 5 revtex pages, no figures, accepted for publication in Phys. Rev.
General unifying features of controlled quantum phenomena
Many proposals have been put forth for controlling quantum phenomena,
including open-loop, adaptive feedback, and real-time feedback control. Each of
these approaches has been viewed as operationally, and even physically,
distinct from the others. This work shows that all such scenarios inherently
share the same fundamental control features residing in the topology of the
landscape relating the target physical observable to the applied controls. This
unified foundation may provide a basis for development of hybrid control
schemes that would combine the advantages of the existing approaches to achieve
the best overall performance.Comment: The published version (includes the supplementary material
Asymmetric embedding in brane cosmology
We derive a system of cosmological equations for a braneworld with induced
curvature which is a junction between several bulk spaces. The permutation
symmetry of the bulk spaces is not imposed, and the values of the fundamental
constants, and even the signatures of the extra dimension, may be different on
different sides of the brane. We then consider the usual partial case of two
asymmetric bulk spaces and derive an exact closed system of scalar equations on
the brane. We apply this result to the cosmological evolution on such a brane
and describe its various partial cases.Comment: 10 page
5D Black Holes and Strings with Higher Derivatives
We find asymptotically flat black hole and string solutions to 5D
supergravity in the presence of higher derivative terms. In some cases,
including the fundamental heterotic string solution, the higher derivative
terms smooth out naked singularities into regular geometries carrying zero
entropy. We also compute corrections to the entropy of 5D Calabi-Yau black
holes, and discuss the relation to previous results.Comment: 33 pages, 2 figs., harvmac; v2: typos corrected, references added v3:
refs correcte
Large Charge Four-Dimensional Extremal N=2 Black Holes with R^2-Terms
We consider N=2 supergravity in four dimensions with small R^2 curvature
corrections. We construct large charge extremal supersymmetric and
non-supersymmetric black hole solutions in all space, and analyze their
thermodynamic properties.Comment: 18 pages. v2,3: minor fixe
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