4,363 research outputs found
Escape Time Characterization of Pendular Fabry-Perot
We show that an escape from the potential minimum of Fabry-Perot
interferometers can be detected measuring the associated sudden change of
reflectivity. We demonstrate that the loss of information that occurs retaining
only the sequence of escapes, rather than the full trajectory, can be very mild
and can lead to an effective method to reveal the noise intensity or the
presence of a coherent signal
Tanaka-Tagoshi Parametrization of post-1PN Spin-Free Gravitational Wave Chirps: Equispaced and Cardinal Interpolated Lattices For First Generation Interferometric Antennas
The spin-free binary-inspiral parameter-space introduced by Tanaka and
Tagoshi to construct a uniformly-spaced lattice of templates at (and possibly
beyond) order is shown to work for all first generation interferometric
gravitational wave antennas. This allows to extend the minimum-redundant
cardinal interpolation techniques of the correlator bank developed by the
Authors to the highest available order PN templates. The total number of 2PN
templates to be computed for a minimal match is reduced by a
factor 4, as in the 1PN case.Comment: 9 pages, 8 figures, 3 tables, accepted for publication in Phys. Rev.
Rejection Properties of Stochastic-Resonance-Based Detectors of Weak Harmonic Signals
In (V. Galdi et al., Phys. Rev. E57, 6470, 1998) a thorough characterization
in terms of receiver operating characteristics (ROCs) of stochastic-resonance
(SR) detectors of weak harmonic signals of known frequency in additive gaussian
noise was given. It was shown that strobed sign-counting based strategies can
be used to achieve a nice trade-off between performance and cost, by comparison
with non-coherent correlators. Here we discuss the more realistic case where
besides the sought signal (whose frequency is assumed known) further unwanted
spectrally nearby signals with comparable amplitude are present. Rejection
properties are discussed in terms of suitably defined false-alarm and
false-dismissal probabilities for various values of interfering signal(s)
strength and spectral separation.Comment: 4 pages, 5 figures. Misprints corrected. PACS numbers added. RevTeX
Mode Confinement in Photonic Quasi-Crystal Point-Defect Cavities for Particle Accelerators
In this Letter, we present a study of the confinement properties of
point-defect resonators in finite-size photonic-bandgap structures composed of
aperiodic arrangements of dielectric rods, with special emphasis on their use
for the design of cavities for particle accelerators. Specifically, for
representative geometries, we study the properties of the fundamental mode (as
a function of the filling fraction, structure size, and losses) via 2-D and 3-D
full-wave numerical simulations, as well as microwave measurements at room
temperature. Results indicate that, for reduced-size structures, aperiodic
geometries exhibit superior confinement properties by comparison with periodic
ones.Comment: 4 pages, 4 figures, accepted for publication in Applied Physics
Letter
Detection of noise-corrupted sinusoidal signals with Josephson junctions
We investigate the possibility of exploiting the speed and low noise features
of Josephson junctions for detecting sinusoidal signals masked by Gaussian
noise. We show that the escape time from the static locked state of a Josephson
junction is very sensitive to a small periodic signal embedded in the noise,
and therefore the analysis of the escape times can be employed to reveal the
presence of the sinusoidal component. We propose and characterize two detection
strategies: in the first the initial phase is supposedly unknown (incoherent
strategy), while in the second the signal phase remains unknown but is fixed
(coherent strategy). Our proposals are both suboptimal, with the linear filter
being the optimal detection strategy, but they present some remarkable
features, such as resonant activation, that make detection through Josephson
junctions appealing in some special cases.Comment: 22 pages, 13 figure
Lifetime Ratios of Beauty Hadrons at the Next-to-Leading Order in QCD
We compute the next-to-leading order QCD corrections to spectator effects in
the lifetime ratios of beauty hadrons. With respect to previous calculations,
we take into account the non vanishing value of the charm quark mass. We obtain
the predictions tau(B+)/tau(Bd) = 1.06 +- 0.02, tau(Bs)/tau(Bd)= 1.00 +- 0.01
and tau(Lambdab)/tau(Bd) = 0.90 +- 0.05, in good agreement with the
experimental results. In the case of tau(Bs)/tau(Bd) and tau(Lambdab)/tau(Bd),
however, some contributions, which either vanish in the vacuum insertion
approximation or represent a pure NLO corrections, have not been determined
yet.Comment: 24 pages, 4 figure
Next-to-Leading Order QCD Corrections to Spectator Effects in Lifetimes of Beauty Hadrons
Theoretical predictions of beauty hadron lifetimes, based on the heavy quark
expansion up to and including order 1/mb^2, do not to reproduce the
experimental measurements of the lifetime ratios tau(B+)/tau(Bd) and
tau(Lambdab)/tau(Bd). Large corrections to these predictions come from
phase-space enhanced 1/mb^3 contributions, i.e. hard spectator effects. In this
paper we calculate the next-to-leading order QCD corrections to the Wilson
coefficients of the local operators appearing at O(1/mb^3). We find that these
corrections improve the agreement with the experimental data. The lifetime
ratio of charged to neutral B mesons, tau(B+)/tau(Bd), turns out to be in very
good agreement with the corresponding measurement, whereas for tau(Bs)/tau(Bd)
and tau(Lambdab)/tau(Bd) there is a residual difference at the 1-sigma level.
We discuss, however, why the theoretical predictions are less accurate in the
latter cases.Comment: 29 pages, 7 figures, uses epsf. Misprints in eqs. (28) and (52)
corrected. Results unchanged. Final version to appear on Nucl.Phys.
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