23 research outputs found
Stochastic virtual tests for fiber composites
We will describe a Virtual Test system for continuous fiber composites. The virtual test draws from a new wave of advanced experiments and theory that address physical, mathematical, and engineering aspects of material definition and failure prediction. The methods go far beyond currently standard tests and conventional FEM analysis to challenge our conception of what can constitute a practicable engineering approach. Emphasis will be given to high temperature ceramic matrix composites with textile reinforcement, which have been the subject material of the National Hypersonic Science Center, Materials and Structures, a joint AFOSR/NASA program. However, thematic topics also address generic fiber composites. Development has been organized as a “pipeline” that links the separate disciplinary efforts of groups housed in seven institutions spread across the United States. The main research steps are: high resolution three-dimensional (3D) imaging of the microstructure, statistical characterization of the microstructure, formulation of a probabilistic generator for creating virtual specimens that replicate the measured statistics, creation of a computational model for a virtual specimen that allows general representation of discrete damage events, calibration of the model using room and high temperature tests, simulation of failure, and model validation. Key new experiments include digital surface image correlation and µm-resolution 3D computed tomography imaging of the microstructure and evolving damage, both executed at temperatures exceeding 1500°C. Conceptual advances include using both geometry and topology to characterize stochastic microstructures. Computational methods include new probabilistic algorithms for generating stochastic virtual specimens and a new Augmented Finite Element Method that yields extreme efficiency in dealing with arbitrary cracking in heterogeneous materials. The challenge of relating variance in engineering properties to stochastic microstructure in a computationally tractable manner, while retaining necessary physical details in models, will be discussed
First Observation of CP Violation in B0->D(*)CP h0 Decays by a Combined Time-Dependent Analysis of BaBar and Belle Data
We report a measurement of the time-dependent CP asymmetry of B0->D(*)CP h0
decays, where the light neutral hadron h0 is a pi0, eta or omega meson, and the
neutral D meson is reconstructed in the CP eigenstates K+ K-, K0S pi0 or K0S
omega. The measurement is performed combining the final data samples collected
at the Y(4S) resonance by the BaBar and Belle experiments at the
asymmetric-energy B factories PEP-II at SLAC and KEKB at KEK, respectively. The
data samples contain ( 471 +/- 3 ) x 10^6 BB pairs recorded by the BaBar
detector and ( 772 +/- 11 ) x 10^6, BB pairs recorded by the Belle detector. We
measure the CP asymmetry parameters -eta_f S = +0.66 +/- 0.10 (stat.) +/- 0.06
(syst.) and C = -0.02 +/- 0.07 (stat.) +/- 0.03 (syst.). These results
correspond to the first observation of CP violation in B0->D(*)CP h0 decays.
The hypothesis of no mixing-induced CP violation is excluded in these decays at
the level of 5.4 standard deviations.Comment: 9 pages, 2 figures, submitted to Physical Review Letter
Measurement of in with decays by a combined time-dependent Dalitz plot analysis of BaBar and Belle data
We report measurements of and from a
time-dependent Dalitz plot analysis of with decays, where the light unflavored and neutral
hadron is a , , or meson. The analysis is
performed with a combination of the final data sets of the \babar\ and Belle
experiments containing and
pairs collected at the resonance at the
asymmetric-energy B factories PEP-II at SLAC and KEKB at KEK, respectively. We
measure and . The result for the direct
measurement of the angle is . The last quoted
uncertainties are due to the composition of the decay amplitude model, which is newly established by a Dalitz plot
amplitude analysis of a high-statistics data sample
as part of this analysis. We find the first evidence for at the
level of standard deviations. The measurement excludes the trigonometric
multifold solution at the level of
standard deviations and therefore resolves an ambiguity in the
determination of the apex of the CKM Unitarity Triangle. The hypothesis of
is ruled out at the level of standard deviations, and
thus CP violation is observed in decays.Comment: To be submitted to Physical Review
The Physics of the B Factories
This work is on the Physics of the B Factories. Part A of this book contains a brief description of the SLAC and KEK B Factories as well as their detectors, BaBar and Belle, and data taking related issues. Part B discusses tools and methods used by the experiments in order to obtain results. The results themselves can be found in Part C
Neutrinos
229 pages229 pages229 pagesThe Proceedings of the 2011 workshop on Fundamental Physics at the Intensity Frontier. Science opportunities at the intensity frontier are identified and described in the areas of heavy quarks, charged leptons, neutrinos, proton decay, new light weakly-coupled particles, and nucleons, nuclei, and atoms
Stochastic virtual tests for high-temperature ceramic matrix composites
We review the development of virtual tests for high-temperature ceramic matrix composites with textile reinforcement. Success hinges on understanding the relationship between the microstructure of continuous-fiber composites, including its stochastic variability, and the evolution of damage events leading to failure. The virtual tests combine advanced experiments and theories to address physical, mathematical, and engineering aspects of material definition and failure prediction. Key new experiments include surface image correlation methods and synchrotron-based, micrometer-resolution 3D imaging, both executed at temperatures exceeding 1,500°C. Computational methods include new probabilistic algorithms for generating stochastic virtual specimens, as well as a new augmented finite element method that deals efficiently with arbitrary systems of crack initiation, bifurcation, and coalescence in heterogeneous materials. Conceptual advances include the use of topology to characterize stochastic microstructures. We discuss the challenge of predicting the probability of an extreme failure event in a computationally tractable manner while retaining the necessary physical detail
First Observation of C
9 pages, 2 figures.International audienceWe report a measurement of the time-dependent CP asymmetry of B0->D(*)CP h0 decays, where the light neutral hadron h0 is a pi0, eta or omega meson, and the neutral D meson is reconstructed in the CP eigenstates K+ K-, K0S pi0 or K0S omega. The measurement is performed combining the final data samples collected at the Y(4S) resonance by the BaBar and Belle experiments at the asymmetric-energy B factories PEP-II at SLAC and KEKB at KEK, respectively. The data samples contain ( 471 +/- 3 ) x 10^6 BB pairs recorded by the BaBar detector and ( 772 +/- 11 ) x 10^6, BB pairs recorded by the Belle detector. We measure the CP asymmetry parameters -eta_f S = +0.66 +/- 0.10 (stat.) +/- 0.06 (syst.) and C = -0.02 +/- 0.07 (stat.) +/- 0.03 (syst.). These results correspond to the first observation of CP violation in B0->D(*)CP h0 decays. The hypothesis of no mixing-induced CP violation is excluded in these decays at the level of 5.4 standard deviations
Measurement of in with decays by a combined time-dependent Dalitz plot analysis of BaBar and Belle data
We report measurements of and from a time-dependent Dalitz plot analysis of with decays, where the light unflavored and neutral hadron is a , , or meson. The analysis is performed with a combination of the final data sets of the \babar\ and Belle experiments containing and pairs collected at the resonance at the asymmetric-energy B factories PEP-II at SLAC and KEKB at KEK, respectively. We measure and . The result for the direct measurement of the angle is . The last quoted uncertainties are due to the composition of the decay amplitude model, which is newly established by a Dalitz plot amplitude analysis of a high-statistics data sample as part of this analysis. We find the first evidence for at the level of standard deviations. The measurement excludes the trigonometric multifold solution at the level of standard deviations and therefore resolves an ambiguity in the determination of the apex of the CKM Unitarity Triangle. The hypothesis of is ruled out at the level of standard deviations, and thus CP violation is observed in decays