4,266 research outputs found
Electromagnetic penguin operators and direct CP violation in K --> pi l^+ l^-
Supersymmetric extensions of the Standard Model predict a large enhancement
of the Wilson coefficients of the dimension-five electromagnetic penguin
operators affecting the direct CP violation in K_L --> pi^0 e^+ e^- and the
charge asymmetry in K^\pm --> pi^\pm l^+ l^-.
Here we compute the relevant matrix elements in the chiral quark model and
compare these with the ones given by lattice calculationsComment: 12 pages, JHEP style, gluonic corrections to B_T adde
Effects of mode degeneracy in the LIGO Livingston Observatory recycling cavity
We analyze the electromagnetic fields in a Pound-Drever-Hall locked,
marginally unstable, Fabry-Perot cavity as a function of small changes in the
cavity length during resonance. More specifically, we compare the results of a
detailed numerical model with the behavior of the recycling cavity of the Laser
Interferometer Gravitational-wave Observatory (LIGO) detector that is located
in Livingston, Louisiana. In the interferometer's normal mode of operation, the
recycling cavity is stabilized by inducing a thermal lens in the cavity mirrors
with an external CO2 laser. During the study described here, this thermal
compensation system was not operating, causing the cavity to be marginally
optically unstable and cavity modes to become degenerate. In contrast to stable
optical cavities, the modal content of the resonating beam in the uncompensated
recycling cavity is significantly altered by very small cavity length changes.
This modifies the error signals used to control the cavity length in such a way
that the zero crossing point is no longer the point of maximum power in the
cavity nor is it the point where the input beam mode in the cavity is
maximized.Comment: Eight pages in two-column format. Six color figures. To be published
JOSA
Model of Thermal Wavefront Distortion in Interferometric Gravitational-Wave Detectors I: Thermal Focusing
We develop a steady-state analytical and numerical model of the optical
response of power-recycled Fabry-Perot Michelson laser gravitational-wave
detectors to thermal focusing in optical substrates. We assume that the thermal
distortions are small enough that we can represent the unperturbed intracavity
field anywhere in the detector as a linear combination of basis functions
related to the eigenmodes of one of the Fabry-Perot arm cavities, and we take
great care to preserve numerically the nearly ideal longitudinal phase
resonance conditions that would otherwise be provided by an external
servo-locking control system. We have included the effects of nonlinear thermal
focusing due to power absorption in both the substrates and coatings of the
mirrors and beamsplitter, the effects of a finite mismatch between the
curvatures of the laser wavefront and the mirror surface, and the diffraction
by the mirror aperture at each instance of reflection and transmission. We
demonstrate a detailed numerical example of this model using the MATLAB program
Melody for the initial LIGO detector in the Hermite-Gauss basis, and compare
the resulting computations of intracavity fields in two special cases with
those of a fast Fourier transform field propagation model. Additional
systematic perturbations (e.g., mirror tilt, thermoelastic surface
deformations, and other optical imperfections) can be included easily by
incorporating the appropriate operators into the transfer matrices describing
reflection and transmission for the mirrors and beamsplitter.Comment: 24 pages, 22 figures. Submitted to JOSA
On the Analytic Structure of a Family of Hyperboloidal Beams of Potential Interest for Advanced LIGO
For the baseline design of the advanced Laser Interferometer
Gravitational-wave Observatory (LIGO), use of optical cavities with
non-spherical mirrors supporting flat-top ("mesa") beams, potentially capable
of mitigating the thermal noise of the mirrors, has recently drawn a
considerable attention. To reduce the severe tilt-instability problems
affecting the originally conceived nearly-flat, "Mexican-hat-shaped" mirror
configuration, K. S. Thorne proposed a nearly-concentric mirror configuration
capable of producing the same mesa beam profile on the mirror surfaces.
Subsequently, Bondarescu and Thorne introduced a generalized construction that
leads to a one-parameter family of "hyperboloidal" beams which allows
continuous spanning from the nearly-flat to the nearly-concentric mesa beam
configurations. This paper is concerned with a study of the analytic structure
of the above family of hyperboloidal beams. Capitalizing on certain results
from the applied optics literature on flat-top beams, a physically-insightful
and computationally-effective representation is derived in terms of
rapidly-converging Gauss-Laguerre expansions. Moreover, the functional relation
between two generic hyperboloidal beams is investigated. This leads to a
generalization (involving fractional Fourier transform operators of complex
order) of some recently discovered duality relations between the nearly-flat
and nearly-concentric mesa configurations. Possible implications and
perspectives for the advanced LIGO optical cavity design are discussed.Comment: 9 pages, 6 figures, typos corrected, Eqs. (24) and (26) change
Kaon decay interferometry as meson dynamics probes
We discuss the time dependent interferences between and in the
decays in and , to be studied at interferometry machines
such as the -factory and LEAR. We emphasize the possibilities and the
advantages of using interferences, in comparison with width measurements, to
obtain information both on conserving and violating amplitudes.
Comparison with present data and suggestions for future experiments are made.Comment: 15 pages, in RevTex, Report INFNNA-IV-93-31, UTS-DFT-93-2
Normal metal tunnel junction-based superconducting quantum interference proximity transistor: the N-SQUIPT
We report the fabrication and characterization of an alternative design for a
superconducting quantum interference proximity transistor (SQUIPT) based on a
normal metal (N) probe. The absence of direct Josephson coupling between the
proximized metal nanowire and the N probe allows us to observe the full
modulation of the wire density of states around zero voltage and current
\textit{via} the application of an external magnetic field. This results into a
drastic suppression of power dissipation which can be as low as a few W. In this context the interferometer allows an improvement of up to
four orders of magnitude with respect to earlier SQUIPT designs, and makes it
ideal for extra-low power cryogenic applications. In addition, the N-SQUIPT has
been recently predicted to be the enabling candidate for the implementation of
coherent caloritronic devices based on proximity effect.Comment: 5 pages, 4 color figure
The dependence of test-mass thermal noises on beam shape in gravitational-wave interferometers
In second-generation, ground-based interferometric gravitational-wave
detectors such as Advanced LIGO, the dominant noise at frequencies
Hz to Hz is expected to be due to thermal fluctuations in the
mirrors' substrates and coatings which induce random fluctuations in the shape
of the mirror face. The laser-light beam averages over these fluctuations; the
larger the beam and the flatter its light-power distribution, the better the
averaging and the lower the resulting thermal noise. In semi-infinite mirrors,
scaling laws for the influence of beam shape on the four dominant types of
thermal noise (coating Brownian, coating thermoelastic, substrate Brownian, and
substrate thermoelastic) have been suggested by various researchers and derived
with varying degrees of rigour. Because these scaling laws are important tools
for current research on optimizing the beam shape, it is important to firm up
our understanding of them. This paper (1) gives a summary of the prior work and
of gaps in the prior analyses, (2) gives a unified and rigorous derivation of
all four scaling laws, and (3) explores, relying on work by J. Agresti,
deviations from the scaling laws due to finite mirror size.Comment: 25 pages, 10 figures, submitted to Class. Quantum Gra
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