141 research outputs found
Analysis of second harmonic generation in photonic-crystal-assisted waveguides
We study second harmonic generation in a planar dielectric waveguide having a
low-index, polymer core layer, bounded by two multilayer stacks. This geometry
allows exceptionally strong confinement of the light at the fundamental
wavelength inside the core region with virtually zero net propagation losses
for distances that exceed several centimeters, provided material and scattering
losses are neglected. A phase-matched configuration of the waveguide is
reported in which the pump signal is the lowest-order mode of the waveguide,
and the generated second harmonic signal corresponds to the third propagation
mode of the waveguide. Using a polymer waveguide core, having chi(2)=100 pm/V,
we predict a conversion efficiency of approximately 90% after a propagation
distance of 2 mm, using peak pump intensities inside the core of the waveguide
of 1.35 GW/cm^2. If the waveguide core contains polymer layers with different
glass transition temperatures, the layers can be poled independently to
maximize the overlap integral, and similar pump depletions may be achieved over
a distance of approximately 500 microns.Comment: 20 pages, 7 figures, 330k
Superfici autopulenti e biocide nel restauro archeologico di pietre e laterizi
Archaeological artifacts are inevitably subject to deterioration caused by natural air pollution, contaminants by human actions, and biodeterioration from microorganisms. Their preservation is considered a more and more strategic factor in many countries because of their economic, social and cultural implications. Modern techniques of interventions often require re-application after some years, and they cannot be used in all restorations. Recently, the use of nanotechnologies was transferred to the restoration sector bringing many innovations. Titanium dioxide (TiO2) is the main nanostructured material used to prevent the comparison of weathering traces, to obtain self-cleaning materials and to slow down biofouling as well. In this paper, its potential use was tested on common archaeological materials like sandstone, limestone and bricks. The self-cleaning ability of this innovative material, as well as, its biofouling prevention were evaluated in laboratory simulated tests. Results show the high potentiality of this nanomaterial in making the tested archaeological surfaces self-cleaning and biocide
A vision-based system to support tactical and physical analyses in futsal
This paper presents a vision-based system to support tactical and physical analyses of futsal teams. Most part of the current analyses in this sport are manually performed, while the existing solutions based on automatic approaches are frequently composed of costly and complex tools, developed for other kind of team sports, making it difficult their adoption by futsal teams. Our system, on the other hand, represents a simple yet efficient dedicated solution, which is based on the analyses of image sequences captured by a single stationary camera used to obtain top-view images of the entire court. We use adaptive background subtraction and blob analysis to detect players, as well as particle filters to track them in every video frame. The system determines the distance traveled by each player, his/her mean and maximum speeds, as well as generates heat maps that describe players’ occupancy during the match. To present the collected data, our system uses a specially developed mobile application. Experimental results with image sequences of an official match and a training match show that our system provides data with global mean tracking errors below 40 cm, demanding on 25 ms to process each frame and, thus, demonstrating its high application potential
Measurement of the B+ --> p pbar K+ Branching Fraction and Study of the Decay Dynamics
With a sample of 232x10^6 Upsilon(4S) --> BBbar events collected with the
BaBar detector, we study the decay B+ --> p pbar K+ excluding charmonium decays
to ppbar. We measure a branching fraction Br(B+ --> p pbar
K+)=(6.7+/-0.5+/-0.4)x10^{-6}. An enhancement at low ppbar mass is observed and
the Dalitz plot asymmetry suggests dominance of the penguin amplitude in this B
decay. We search for a pentaquark candidate Theta*++ decaying into pK+ in the
mass range 1.43 to 2.00 GeV/c2 and set limits on Br(B+ -->
Theta*++pbar)xBr(Theta*++ --> pK+) at the 10^{-7} level.Comment: 8 pages, 7 postscript figures, submitted to Phys. Rev. D (Rapid
Communications
Search for the W-exchange decays B0 --> Ds(*)- Ds(*)+
We report a search for the decays , , in a sample of 232
million decays to \BBb ~pairs collected with the \babar detector
at the PEP-II asymmetric-energy storage ring. We find no significant
signal and set upper bounds for the branching fractions: and at 90% confidence level.Comment: 8 pages, 2 figures, submitted to PRD-R
Measurement of D^0-D̅ ^0 Mixing from a Time-Dependent Amplitude Analysis of D^0→K^+π^-π^0 Decays
We present evidence of D^0-D̅ ^0 mixing using a time-dependent amplitude analysis of the decay D^0→K^+π^-π^0 in a data sample of 384 fb^(-1) collected with the BABAR detector at the PEP-II e^+e^- collider at the Stanford Linear Accelerator Center. Assuming CP conservation, we measure the mixing parameters x_(Kππ)^(0′)=[2.61_(-0.68)^(+0.57)(stat)±0.39(syst)]%, y_(Kππ)^(0′)=[-0.06_(-0.64)^(+0.55)(stat)±0.34(syst)]%. This result is inconsistent with the no-mixing hypothesis with a significance of 3.2 standard deviations. We find no evidence of CP violation in mixing
Study of hadronic transitions between Υ states and observation of Υ(4S) → ηΥ(1S) decay
We present a study of hadronic transitions between Υ(mS) (m = 4, 3, 2) and Υ(nS) (n = 2, 1) resonances based on 347.5 fb^(-1) of data taken with the BABAR detector at the PEP-II storage rings.
We report the first observation of Υ(4S) → ηΥ(1S) decay with a branching fraction [script B](Υ(4S) → ηΥ(1S)) = (1.96±0.06_(stat)±0.09_(syst))×10^(-4) and measure the ratio of partial widths Γ(Υ(4S) → ηΥ(1S))/Γ(Υ(4S) → π^+π^-Υ(1S))=2.41±0.40_(stat)±0.12_(syst). We set 90% CL upper limits on the ratios Γ(Υ(2S) → ηΥ(1S))/Γ(Υ(2S) → π^+π^-Υ(1S))<5.2×10^(-3) and Γ(Υ(3S) → ηΥ(1S))/Γ(Υ (3S) → π^+π^-Υ(1S))<1.9×10^(-2). We also present new measurements of the ratios Γ(Υ(4S) → π^+π^-Υ(2S))/Γ(Υ(4S) → π^+ π^-Υ(1S))=1.16±0.16_(stat)±0.14_(syst) and Γ(Υ(3S) → π^+π^-Υ(2S))/Γ(Υ(3S) → π^+ π^-Υ(1S))=0.577±0.026_(stat)±0.060_(syst)
Measurements of branching fractions for B^+ → p^+γ, B^0 → p^0γ, and B^0 → ωγ
We present branching fraction measurements for the radiative decays B^+ → ρ^+ γ, B^0 → ρ^0 γ, and B^0 → ωγ. The analysis is based on a data sample of 465 × 10^6 B[overline B] events collected with the BABAR detector at the PEP-II asymmetric-energy B Factory located at the Stanford Linear Accelerator Center. We find [script B](B^+ → ρ^+ γ) = (1.20_(-0.37)^(+0.42) ± 0.20) × 10^(-6), [script B](B^0 → ρ^0γ) = (0.97_(-0.22)^(+0.24) ± 0.06) × 10^(-6), and a 90% C.L. upper limit [script B](B^0 → ωγ) < 0.9 × 10^(-6), where the first error is statistical and the second is systematic. We also measure the isospin-violating quantity Γ(B^+ → ρ^+ γ)/2Γ(B^0 → ρ^0γ)-1 = -0.43_(-0.22)^(+0.25)±0.10
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