1,243 research outputs found
Using an extended Kalman filter learning algorithm for feed-forward neural networks to describe tracer correlations
International audienceIn this study a new extended Kalman filter (EKF) learning algorithm for feed-forward neural networks (FFN) is used. With the EKF approach, the training of the FFN can be seen as state estimation for a non-linear stationary process. The EKF method gives excellent convergence performances provided that there is enough computer core memory and that the machine precision is high. Neural networks are ideally suited to describe the spatial and temporal dependence of tracer-tracer correlations. The neural network performs well even in regions where the correlations are less compact and normally a family of correlation curves would be required. For example, the CH4-N2O correlation can be well described using a neural network trained with the latitude, pressure, time of year, and CH4 volume mixing ratio (v.m.r.). The neural network was able to reproduce the CH4-N2O correlation with a correlation coefficient between simulated and training values of 0.9997. The neural network Fortran code used is available for download
Using neural networks to describe tracer correlations
Neural networks are ideally suited to describe the spatial and temporal dependence of tracer-tracer correlations. The neural network performs well even in regions where the correlations are less compact and normally a family of correlation curves would be required. For example, the CH<sub>4</sub>-N<sub>2</sub>O correlation can be well described using a neural network trained with the latitude, pressure, time of year, and methane volume mixing ratio (v.m.r.). In this study a neural network using Quickprop learning and one hidden layer with eight nodes was able to reproduce the CH<sub>4</sub>-N<sub>2</sub>O correlation with a correlation coefficient between simulated and training values of 0.9995. Such an accurate representation of tracer-tracer correlations allows more use to be made of long-term datasets to constrain chemical models. Such as the dataset from the Halogen Occultation Experiment (HALOE) which has continuously observed CH<sub>4 </sub> (but not N<sub>2</sub>O) from 1991 till the present. The neural network Fortran code used is available for download
Evidence for a new resonance and search for the Y(4140) in
The process \gamma \gamma \to \phi \jpsi is measured for \phi \jpsi
masses between threshold and 5 GeV/, using a data sample of 825
fb collected with the Belle detector. A narrow peak of
events, with a significance of 3.2 standard deviations
including systematic uncertainty, is observed. The mass and natural width of
the structure (named X(4350)) are measured to be
and
, respectively. The
product of its two-photon decay width and branching fraction to \phi\jpsi is
for , or
for . No
signal for the Y(4140)\to \phi \jpsi structure reported by the CDF
Collaboration in B\to K^+ \phi \jpsi decays is observed, and limits of
\Gamma_{\gamma \gamma}(Y(4140)) \BR(Y(4140)\to\phi \jpsi)<41 \hbox{eV} for
or for are determined at the 90% C.L. This
disfavors the scenario in which the Y(4140) is a molecule.Comment: 9 pages, 3 figures, publication in Phys. Rev. Lett. 104, 112004, 201
Search for charmonium and charmonium-like states in \Upsilon(2S) radiative decays
Using a sample of 158 million \Upsilon(2S) events collected with the Belle
detector, charmonium and charmonium-like states with even charge parity are
searched for in \Upsilon(2S) radiative decays. No significant \chi_{cJ} or
\eta_c signal is observed and the following upper limits at 90% confidence
level (C.L.) are obtained: BR(\Upsilon(2S)\to \gamma \chi_{c0})< 1.0 \times
10^{-4}, BR(\Upsilon(2S) \to \gamma \chi_{c1})<3.6 \times 10^{-6},
BR(\Upsilon(2S) \to \gamma \chi_{c2})<1.5 \times 10^{-5}, and BR(\Upsilon(2S)
\to \gamma \eta_c)< 2.7 \times 10^{-5}. No significant signal of any
charmonium-like state is observed, and we obtain the limits \BR(\Upsilon(2S)\to
\gamma X(3872))\times\BR(X(3872)\to\pi^+\pi^-J/\psi)< 0.8 \times 10^{-6},
BR(\Upsilon(2S) \to \gamma X(3872))\times BR(X(3872)\to\pi^+\pi^-\pi^0 J/\psi)<
2.4\times 10^{-6}, BR(\Upsilon(2S) \to \gamma X(3915))\times
BR(X(3915)\to\omega J/\psi)< 2.8\times 10^{-6}, BR(\Upsilon(2S) \to \gamma
Y(4140))\times BR(Y(4140)\to\phi J/\psi)) < 1.2\times 10^{-6}, and
BR(\Upsilon(2S) \to \gamma X(4350))\times BR(X(4350)\to\phi J/\psi))< 1.3\times
10^{-6} at 90% C.L.Comment: 7 pages, 6 figures, 1 tabl
Search for the decay at Belle
We report a search for the rare charmless decay
using a data sample of
pairs collected at the resonance with
the Belle detector at the KEKB asymmetric-energy collider. No
statistically significant signal is found and a 90% confidence-level upper
limit is set on the decay branching fraction as .Comment: 8 pages, 3 figures, submitted to PRD(RC
Search for double charmonium decays of the P-wave spin-triplet bottomonium states
Using a sample of 158 million events collected with the Belle
detector, we search for the first time for double charmonium decays of the
-wave spin-triplet bottomonium states (,
\chi_{bJ} \to \jpsi \jpsi, \jpsi \psp, \psp \psp for J=0, 1, and 2). No
significant signal is observed in the double charmonium mass
spectra, and we obtain the following upper limits, \BR(\chi_{bJ} \to \jpsi
\jpsi)<7.1\times 10^{-5}, , ,
\BR(\chi_{bJ} \to \jpsi \psp)<1.2\times 10^{-4}, ,
, \BR(\chi_{bJ} \to \psp \psp)<3.1\times 10^{-5},
, for J=0, 1, and 2, respectively, at
the 90% confidence level. These limits are significantly lower than the central
values (with uncertainties of 50% to 70%) predicted using the light cone
formalism but are consistent with calculations using the NRQCD factorization
approach.Comment: 7 pages, 4 figures, 1 tabl
Observation of and search for in B decays
We report a study of and
decay modes using events collected at the
\Upsilon(4S)e^+ e^-X(3872) \to J/\psi \gamma\chi_{c2} \to J/\psi \gammaB\to (X_{c\bar{c}}\gamma) KX(3872) \to \psi' \gamma\mathcal{B}(B^{\pm} \to X(3872)
K^{\pm}) \mathcal{B}(X(3872) \to J/\psi\gamma)=(1.78^{+0.48}_{-0.44}\pm
0.12)\times 10^{-6}\mathcal{B} (B^{\pm} \to\chi_{c2} K^{\pm})=(1.11^{+0.36}_{-0.34} \pm 0.09) \times 10^{-5}\mathcal{B}(B^{\pm} \to
X(3872) K^{\pm}) \mathcal{B}(X(3872) \to \psi'\gamma)<3.45\times 10^{-6}$
(upper limit at 90% C.L.) and also provide upper limits for other searches.Comment: 6 pages, 3 figure
Measurements of the masses and widths of the and baryons
We present measurements of the masses and decay widths of the baryonic states
and using a data sample
corresponding to an integrated luminosity of 711 fb collected with the
Belle detector at the KEKB asymmetric-energy collider operating at
the resonance. We report the mass differences with respect to
the baryon MeV/, MeV/,
MeV/, MeV/, and the decay widths
MeV/,
MeV/,
MeV/,
MeV/,
where the first uncertainties are statistical and the second are systematic.
The isospin mass splittings are measured to be
MeV/ and
MeV/. These results are the most precise to date.Comment: 13 pages, 4 figures, Submitted to PRD(RC
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