709 research outputs found
K* resonance effects on direct CP violation in B -> pi pi K
Charged and neutral B decays into two charged pions and a charged or a
neutral kaon are analyzed within the QCD factorization scheme where final state
interactions before and after hadronization are included. The K*(892) and
K*(1430) resonance effects are taken into account using the presently known
pion-Kaon strange vector and scalar form factors. The weak decay amplitudes,
which are calculated at leading power in Lambda_QCD/m_b and at the
next-to-leading order in the strong coupling constant, include the hard
scattering and annihilation contributions. The end point divergences of these
weak final state interactions are controlled by two complex parameters
determined through a fit to the available effective mass and helicity angle
distribution, CP asymmetry and K*(892) branching ratio data. The predicted
K*(1430) branching ratios and the calculated direct CP violation asymmetries
are compared to the Belle and BABAR Collaboration data.Comment: Comments: 22 pages, 2 figures and 3 tables. In this new version, the
results are unchanged, but, the last paragraph of the Section "RESULTS AND
SUMMARY" (now called "RESULTS AND DISCUSSION") has been replaced by a new
Section "SUMMARY AND OUTLOOK". To appear in Physical Review
Precision determination of the pi-N scattering lengths and the charged pi-NN coupling constant
We critically evaluate the isovector GMO sumrule for the charged
coupling constant using recent precision data from p and d atoms
and with careful attention to systematic errors. From the d scattering
length we deduce the pion-proton scattering lengths (statistic) (systematic))~ and . From this a direct evaluation gives (statistic)(systematic) or .Comment: 4 pages, 1 figure, latex and postscript; invited talk at PANIC99; to
appear in Nucl. Phys. A; changed notation: g^2 and f^2 replaced by
conventional g^2/4\pi and f^2/4\p
Resonances and weak interactions in decays
We describe the -wave in decays using
a unitary model for the Final State Interactions (FSI). The three body
decay is treated as a quasi two-body process where, at the weak vertex, the D
meson decays into a resonance and a pion. The weak part of the decay amplitude
is evaluated using the effective weak Hamiltonian within the factorization
approximation.Comment: 4 pages. Contribution to the X Hadron Physics, Florianopolis-Brazil,
March 26-31, 200
The Pion-Nucleon coupling constant from np charge exchange scattering
A novel extrapolation method has been used to deduce the charged Pion-Nucleon
coupling constant from backward differential scattering cross sections. We
applied it to new measurements performed at 162 MeV at the The Svedberg
Laboratory in Uppsala. In the angular range , the
carefully normalized data are steeper than those of most previous measurements.
The extracted value, , in good agreement with
the classical value, is higher than those determined in recent nucleon-nucleon
partial-wave analyses.Comment: 6 pages, 3 encapsulated figures, epsfig, menu97.cls (included
Pseudoscalar-scalar transition form factors in covariant light front dynamics
In an explicitly covariant light-front formalism, we analyze transition form
factors between pseudoscalar and scalar mesons. Application is performed in
case of the transition in the full available transfer momentum
range .Comment: 4 pages, 4 figures. Talk given at the XXXIII International Conference
on High Energy Physics, ICHEP06, Moscow, 26 July-02 Augus
Un tour d'horizon des approches pour la manipulation des données du web
Le passage au web 2.0 a renforcé le principe selon lequel les données doivent être séparées de leurs présentations. En même temps, le nombre des formats de documents XML a largement évolué sur le web. Les bases de données sont également utilisées pour le fonctionnement des sites. Ces constats impliquent la mise en œuvre d’approches et d’outils associés dédiés à la manipulation des données du web. Certaines de ces approches travaillent directement sur les données, tandis que d’autres se basent sur les schémas de ces mêmes données. L’ingénierie dirigée par les modèles (IDM) forme également une approche candidate à la manipulation des données du web. Dans cet article, nous présentons et comparons les différentes techniques majeures de manipulation de données afin de mettre en exergue leurs avantages et leurs inconvénients pour le problème des données du web
Malan: a mapping language for the data manipulation
Malan is a MApping LANguage that allows the generation of transformation programs by specifying a schema mapping between a source and target data schema. By working at the schema level, Malan remains independent of any transformation process; it also naturally guarantees the correctness of the transformation target relative to its schema. Moreover, by expressing schemas as UML class diagrams, Malan schema mappings can be written on top of UML modellers. This paper describes the overall approach by focusing on the Malan language itself, and its use within a transformation process
Form factors in B->f0(980) and D->f0(980) transitions from dispersion relations
Within the dispersion relation approach we give the double spectral
representation for space-like and time-like B-> f_0(980) and D-> f_0(980)
transition form factors in the full q^2 range. The spectral densities, being
the input of the dispersion relations, are obtained from a triangle diagram in
the relativistic quark model.Comment: Talk given at MESON 2006, Krakow, 9-13 June 200
Molecular evolutionary rates are not correlated with temperature and latitude in Squamata: an exception to the metabolic theory of ecology?
The metabolic theory of ecology stipulates that molecular evolutionary rates should correlate with temperature and latitude in ectothermic organisms. Previous studies have shown that most groups of vertebrates, such as amphibians, turtles and even endothermic mammals, have higher molecular evolutionary rates in regions where temperature is high. However, the association between molecular evolutionary rates and temperature or latitude has never been tested in Squamata.
We used a large dataset including the spatial distributions and environmental variables for 1,651 species of Squamata and compared the contrast of the rates of molecular evolution with the contrast of temperature and latitude between sister species. Using major axis regressions and a new algorithm to choose independent sister species pairs, we found that temperature and absolute latitude were not associated with molecular evolutionary rates.
This absence of association in such a diverse ectothermic group questions the mechanisms explaining current pattern of species diversity in Squamata and challenges the presupposed universality of the metabolic theory of ecology
How precisely can we determine the pion-nucleon coupling constant from the isovector GMO sum rule?
The isovector GMO sum rule for zero energy forward pion-nucleon scattering is
critically studied to obtain the charged pion-nucleon coupling constant using
the precise negatively charged pion-proton and pion-deuteron scattering lengths
deduced recently from pionic atom experiments. This direct determination leads
to a pseudoscalar charged pion-nucleon coupling constant of 14.23 +- 0.09
(statistic) +- 0.17 (systematic). We obtain also accurate values for the
pion-nucleon scattering lengths.Comment: Talk given at the Eighth International Symposium on Meson-Nucleon
Physics and the Structure of the Nucleon, Zuoz, Switzerland, August 15-21,
1999, 5 pages, 2 figures, file menu.cls include
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