514 research outputs found
Degradation of Image Quality Induced by Thermal Loads and Slope Errors in a XUV High Resolution Synchrotron Radiation Monochromator
The limiting effects to the performances of an optical device, such as an XUV monochromator inserted in a synchrotron radiation facility, are mainly manufacturing slope errors and thermal loads induced by the optical beam itself. We have performed numerical simulations on such effects in the low energy section of a high resolution, wide spectral range monochromator for the storage ring ELETTRA in Trieste. The instrument will be used in the dedicated surface physics beamline ALOISA (advanced line for overlayer interface and surface analysis). Thermal effects have been evaluated by using finite element analysis. Thermal induced deformations and slope errors have been included in a ray tracing program. The resulting aberrations at the output of the instrument have been evaluated for the extreme conditions of maximum power density and asymmetrical illumination of the second mirror. The results stress the relevance of manufacturing slope errors in limiting spatial and spectral resolution
Transmittance and optical constants of ca films in the 4-1000 eV spectral range
8 págs.; 8 figs.; OCIS codes: (260.7200) Ultraviolet, extreme; (120.4530) Optical constants; (350.2450) Filters, absorption; (230.4170) Multilayers; (310.6860) Thin films, optical properties.© 2015 Optical Society of America. The low expected absorption of Ca in the extreme ultraviolet (EUV) makes it an attractive material for multilayers and filters because most materials in nature strongly absorb the EUV. Few optical constant data had been reported for Ca. In this research, Ca films of various thicknesses were deposited on gridsupported C films and their transmittance measured in situ from the visible to the soft x-rays. The measurement range contains M2,3 and L2,3 absorption edges. Transmittance measurements were used to obtain the Ca extinction coefficient k. A minimum k of 0.017 was obtained at ∼23 eV, which makes Ca a promising low-absorption material for EUV coatings. A second spectral range of interest for its low absorption is below the Ca L3 edge at ∼343 eV. Measured k data and extrapolations were used to calculate the refractive index n using Kramers.Kronig relations. This is the first self-consistent data set on Ca covering a wide spectral range including the EUV.We acknowledge support by the European
Community—Research Infrastructure Action under
the FP6 “Structuring the European Research Area”
Programme (through the Integrated Infrastructure
Initiative “Integrating Activity on Synchrotron and
Free Electron Laser Science”) through proposal
number Ref. 2007655. This work was also supported
by the National Programme for Space Research,
Subdirección General de Proyectos de Investigación,
Ministerio de Ciencia y Tecnología, project numbers
AYA2010-22032 and AYA2013-42590-P. L. Rodrí-
guez-de Marcos and S. García-Cortés are thankful
to Consejo Superior de Investigaciones Científicas
(CSIC) for funding under the Programa JAE,
partially supported by the European Social Fund.
M. Vidal-Dasilva acknowledges financial support
from an FPI fellowship number BES-2006-14047Peer Reviewe
Search for and Using Genetic Programming Event Selection
We apply a genetic programming technique to search for the double Cabibbo
suppressed decays and .
We normalize these decays to their Cabibbo favored partners and find
\Lambda_c^+ \to p K^+ \pi^-\Lambda_c^+ \to p K^-
\pi^+ and D_s^+ \to K^+ K^+
\pi^-D_s^+ \to K^+ K^- \pi^+ where
the first errors are statistical and the second are systematic. Expressed as
90% confidence levels (CL), we find and respectively.
This is the first successful use of genetic programming in a high energy
physics data analysis.Comment: 10 page
A Non-parametric Approach to Measuring the \kpi{} Amplitudes in \dpkkpi{} Decay
Using a large sample of \dpkkpi{} decays collected by the FOCUS
photoproduction experiment at Fermilab, we present the first non-parametric
analysis of the \kpi{} amplitudes in \dpkkpi{} decay. The technique is similar
to the technique used for our non-parametric measurements of the \krzmndk{}
form factors. Although these results are in rough agreement with those of E687,
we observe a wider S-wave contribution for the \ksw{} contribution than the
standard, PDG \cite{pdg} Breit-Wigner parameterization. We have some weaker
evidence for the existence of a new, D-wave component at low values of the mass.Comment: 13 pages 3 figure
Measurement of the D+ and Ds+ decays into K+K-K+
We present the first clear observation of the doubly Cabibbo suppressed decay
D+ --> K-K+K+ and the first observation of the singly Cabibbo suppressed decay
Ds+ --> K-K+K+. These signals have been obtained by analyzing the high
statistics sample of photoproduced charm particles of the FOCUS(E831)
experiment at Fermilab. We measure the following relative branching ratios:
Gamma(D+ --> K-K+K+)/Gamma(D+ --> K-pi+pi+) = (9.49 +/- 2.17(statistical) +/-
0.22(systematic))x10^-4 and Gamma(Ds+ --> K-K+K+)/Gamma(Ds+ --> K-K+pi+) =
(8.95 +/- 2.12(statistical) +2.24(syst.) -2.31(syst.))x10^-3.Comment: 10 pages, 8 figure
A Non-parametric Approach to the D+ to K*0bar mu+ nu Form Factors
Using a large sample of D+ -> K- pi+ mu+ nu decays collected by the FOCUS
photoproduction experiment at Fermilab, we present the first measurements of
the helicity basis form factors free from the assumption of spectroscopic pole
dominance. We also present the first information on the form factor that
controls the s-wave interference discussed in a previous paper by the FOCUS
collaboration. We find reasonable agreement with the usual assumption of
spectroscopic pole dominance and measured form factor ratios.Comment: 14 pages, 5 figures, and 2 tables. We updated the previous version by
changing some words, removing one plot, and adding two tables. These changes
are mostly stylisti
Study of Hadronic Five-Body Decays of Charmed Mesons
We study the decay of D+ and Ds+ mesons into charged five body final states,
and report the discovery of the decay mode D+ -> K+K-Pi+Pi+Pi-, as well as
measurements of the decay modes D+ -> K-Pi+Pi+Pi+Pi-, Ds+ -> K+K-Pi+Pi+Pi-, Ds+
-> PhiPi+Pi+Pi- and D+/Ds+ -> Pi+Pi+Pi+Pi-Pi-. An analysis of the resonant
substructure is also included, with evidence suggesting that both decays
proceed primarily through an a1 vector resonance.Comment: 11 pages, 3 figure
Dalitz plot analysis of D_s+ and D+ decay to pi+pi-pi+ using the K-matrix formalism
FOCUS results from Dalitz plot analysis of D_s+ and D+ to pi+pi-pi+ are
presented. The K-matrix formalism is applied to charm decays for the first time
to fully exploit the already existing knowledge coming from the light-meson
spectroscopy experiments. In particular all the measured dynamics of the S-wave
pipi scattering, characterized by broad/overlapping resonances and large
non-resonant background, can be properly included. This paper studies the
extent to which the K-matrix approach is able to reproduce the observed Dalitz
plot and thus help us to understand the underlying dynamics. The results are
discussed, along with their possible implications on the controversial nature
of the sigma meson.Comment: To be submitted to Phys.Lett.B A misprint corrected in formula
Measurement of the branching ratio of the decay D^0 -> \pi^-\mu^+\nu relative to D^0 -> K^-\mu^+\nu
We present a new measurement of the branching ratio of the Cabibbo suppressed
decay D^0\to \pi^-\mu^+\nu relative to the Cabibbo favored decay D^0\to
K^-\mu^+\nu and an improved measurement of the ratio
|\frac{f_+^{\pi}(0)}{f_+^{K}(0)}|. Our results are 0.074 \pm 0.008 \pm 0.007
for the branching ratio and 0.85 \pm 0.04 \pm 0.04 \pm 0.01 for the form factor
ratio, respectively.Comment: 13pages, 3 figure
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