7,595 research outputs found
A Global Treatment Of VMD Physics Up To The : I. Annihilations, Anomalies And Vector Meson Partial Widths
The HLS Model, equipped with a mechanism providing the breaking of U(3)/SU(3)
symmetry and an isospin symmetry breaking leading naturally to vector meson
mixing, has been recently shown to successfully account for e^+ e^- \ra
\pi^+\pi^- cross section and for the dipion spectrum in decay. The
present study shows that the full anomalous sector of the HLS model can be
considered and is validated by the experimental data. Indeed, this extended
model provides a successful simultaneous fit to the e^+ e^- \ra \pi^+\pi^-
data together with the available data on e^+ e^- \ra \pi^0\gamma, e^+ e^-
\ra \eta\gamma and e^+ e^- \ra \pi^0 \pi^+\pi^- cross sections. It is shown
that the fit of these data sets also predicts an accurate description of the
\eta/\eta^\prime \ra \pi^+ \pi^- \gamma decays fully consistent with the
reported information on their branching fractions and spectra. Finally, one
also derives from our global fits products of widths of the form \Gamma (V \ra
f_1)\Gamma(V \ra e^+ e^-) and ratios of the form \Gamma (V \ra f_1)/\Gamma
(V \ra f_2) describing decays of vector mesons to several non--leptonic final
states.Comment: 58 pages, 10 figures Corrected a few misprints. Footnote 10 change
A Global Treatment Of VMD Physics Up To The : I. Annihilations, Anomalies And Vector Meson Partial Widths
The HLS Model, equipped with a mechanism providing the breaking of U(3)/SU(3)
symmetry and an isospin symmetry breaking leading naturally to vector meson
mixing, has been recently shown to successfully account for e^+ e^- \ra
\pi^+\pi^- cross section and for the dipion spectrum in decay. The
present study shows that the full anomalous sector of the HLS model can be
considered and is validated by the experimental data. Indeed, this extended
model provides a successful simultaneous fit to the e^+ e^- \ra \pi^+\pi^-
data together with the available data on e^+ e^- \ra \pi^0\gamma, e^+ e^-
\ra \eta\gamma and e^+ e^- \ra \pi^0 \pi^+\pi^- cross sections. It is shown
that the fit of these data sets also predicts an accurate description of the
\eta/\eta^\prime \ra \pi^+ \pi^- \gamma decays fully consistent with the
reported information on their branching fractions and spectra. Finally, one
also derives from our global fits products of widths of the form \Gamma (V \ra
f_1)\Gamma(V \ra e^+ e^-) and ratios of the form \Gamma (V \ra f_1)/\Gamma
(V \ra f_2) describing decays of vector mesons to several non--leptonic final
states.Comment: 58 pages, 10 figures Corrected a few misprints. Footnote 10 change
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
Can VMD improve the estimate of the muon g-2 ?
We show that a VMD based theoretical input allows for a significantly
improved accuracy for the hadronic vacuum polarization of the photon which
contributes to the theoretical estimate of the muon g-2. We also show that the
only experimental piece of information in the decay which cannot be
accounted for is the accepted value for {\rm Br}(\tau \ra \pi \pi \nu_\tau),
while the spectum lineshape is in agreement with expectations from
annihilations.Comment: 6 pages, 1 figure Proceedings of the PhiPsi09, Oct. 13-16, 2009,
Beijing, Chin
In-Medium Effects in Photo- and Neutrino-Induced Reactions on Nuclei
In this talk various aspects of in-medium behavior of hadrons are discussed
with an emphasis on observable effects. It is stressed that final state
interactions can have a major effect on observables and thus have to be
considered as part of the theory. This is demonstrated with examples from
photo-nucleus and neutrino-nucleus interactions.Comment: Invited talk, given by U. Mosel, at MESON2006, 9-th International
Workshop on Meson Production, Interaction and Decay, June 9-13, 2006, Cracow,
Polan
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
A sub-product construction of Poincare-Einstein metrics
Given any two Einstein (pseudo-)metrics, with scalar curvatures suitably
related, we give an explicit construction of a Poincar\'e-Einstein
(pseudo-)metric with conformal infinity the conformal class of the product of
the initial metrics. We show that these metrics are equivalent to ambient
metrics for the given conformal structure. The ambient metrics have holonomy
that agrees with the conformal holonomy. In the generic case the ambient metric
arises directly as a product of the metric cones over the original Einstein
spaces. In general the conformal infinity of the Poincare metrics we construct
is not Einstein, and so this describes a class of non-conformally Einstein
metrics for which the (Fefferman-Graham) obstruction tensor vanishes.Comment: 23 pages Minor correction to section 5. References update
The Making of Cloud Applications An Empirical Study on Software Development for the Cloud
Cloud computing is gaining more and more traction as a deployment and
provisioning model for software. While a large body of research already covers
how to optimally operate a cloud system, we still lack insights into how
professional software engineers actually use clouds, and how the cloud impacts
development practices. This paper reports on the first systematic study on how
software developers build applications in the cloud. We conducted a
mixed-method study, consisting of qualitative interviews of 25 professional
developers and a quantitative survey with 294 responses. Our results show that
adopting the cloud has a profound impact throughout the software development
process, as well as on how developers utilize tools and data in their daily
work. Among other things, we found that (1) developers need better means to
anticipate runtime problems and rigorously define metrics for improved fault
localization and (2) the cloud offers an abundance of operational data,
however, developers still often rely on their experience and intuition rather
than utilizing metrics. From our findings, we extracted a set of guidelines for
cloud development and identified challenges for researchers and tool vendors
Unbounded Human Learning: Optimal Scheduling for Spaced Repetition
In the study of human learning, there is broad evidence that our ability to
retain information improves with repeated exposure and decays with delay since
last exposure. This plays a crucial role in the design of educational software,
leading to a trade-off between teaching new material and reviewing what has
already been taught. A common way to balance this trade-off is spaced
repetition, which uses periodic review of content to improve long-term
retention. Though spaced repetition is widely used in practice, e.g., in
electronic flashcard software, there is little formal understanding of the
design of these systems. Our paper addresses this gap in three ways. First, we
mine log data from spaced repetition software to establish the functional
dependence of retention on reinforcement and delay. Second, we use this memory
model to develop a stochastic model for spaced repetition systems. We propose a
queueing network model of the Leitner system for reviewing flashcards, along
with a heuristic approximation that admits a tractable optimization problem for
review scheduling. Finally, we empirically evaluate our queueing model through
a Mechanical Turk experiment, verifying a key qualitative prediction of our
model: the existence of a sharp phase transition in learning outcomes upon
increasing the rate of new item introductions.Comment: Accepted to the ACM SIGKDD Conference on Knowledge Discovery and Data
Mining 201
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