1,638 research outputs found
Reliability analysis of dynamic systems by translating temporal fault trees into Bayesian networks
Classical combinatorial fault trees can be used to assess combinations of failures but are unable to capture sequences of faults, which are important in complex dynamic systems. A number of proposed techniques extend fault tree analysis for dynamic systems. One of such technique, Pandora, introduces temporal gates to capture the sequencing of events and allows qualitative analysis of temporal fault trees. Pandora can be easily integrated in model-based design and analysis techniques. It is, therefore, useful to explore the possible avenues for quantitative analysis of Pandora temporal fault trees, and we identify Bayesian Networks as a possible framework for such analysis. We describe how Pandora fault trees can be translated to Bayesian Networks for dynamic dependability analysis and demonstrate the process on a simplified fuel system model. The conversion facilitates predictive reliability analysis of Pandora fault trees, but also opens the way for post-hoc diagnostic analysis of failures
Three-Loop Anomalous Dimension of the Heavy Quark Pair Production Current in Non-Relativistic QCD
The three-loop non-mixing contributions to the anomalous dimension of the
leading order quark pair production current in non-relativistic QCD are
computed. It is demonstrated that the renormalization procedure can only be
carried out consistently if the dynamics of both soft and the ultrasoft degrees
of freedom is present for all scales below the heavy quark mass, and if the
soft and ultrasoft renormalization scales are always correlated.Comment: 19 pages, revtex, 5 postscript figures include
Water requirements of floodplain rivers and fisheries: existing decision support tools and pathways for development
Fisheries / Rivers / Flood plains / Hydrology / Ecology / Models / Decision support tools / Environmental impact assessment / Methodology / Databases
CP sensitive observables in chargino production with transverse beam polarization
We consider the process e^+e^-\to\ti\chi^+_i\ti\chi^-_j at a linear
collider with transverse beam polarization. We investigate the
influence of the CP phases on azimuthal asymmetries in
e^+e^-\to\ti\chi^+_i\ti\chi^-_j with subsequent two-body decays
\ti\chi^-_j\to \ti\nu_{\ell}\ell^- and \ti\chi^-_j\to W^-\ti\chi^0_1. We
show that triple product correlations involving the transverse beam
polarization vanish if at least one subsequent chargino decay is not observed.
We derive this result within the Minimal Supersymmetric Standard Model (MSSM)
with complex parameters, however, it holds also in the general MSSM with SUSY
flavour violation.Comment: 19 pages, 6 figure
Weak-scale phenomenology of models with gauge-mediated supersymmetry breaking
We study in some detail the spectral phenomenology of models in which
supersymmetry is dynamically broken and transmitted to the supersymmetric
partners of the quarks, leptons and gauge bosons, and the Higgs bosons
themselves, via the usual gauge interactions. We elucidate the parameter space
of what we consider to be the minimal model, and explore the regions which give
rise to consistent radiative electroweak symmetry breaking. We include the
weak-scale threshold corrections, and show how they considerably reduce the
scale dependence of the results. We examine the sensitivity of our results to
unknown higher-order messenger-sector corrections. We compute the superpartner
spectrum across the entire parameter space, and compare it to that of the
minimal supergravity-inspired model. We delineate the regions where the
lightest neutralino or tau slepton is the next-to-lightest supersymmetric
particle, and compute the lifetime and branching ratios of the NLSP. In
contrast to the minimal supergravity-inspired model, we find that the lightest
neutralino can have a large Higgsino component, of order 50%. Nevertheless, the
neutralino branching fraction to the gravitino and the light Higgs boson
remains small, < 10^{-4}, so the observation of such a decay would point to a
non-minimal Higgs sector.Comment: 22 pages, 16 figures, published versio
A proof of factorization for B -> D pi
We prove that the matrix elements of four fermion operators mediating the
decay B^0 -> D^+ \pi^- and B^- -> D^0 \pi^- factor into the product of a form
factor describing the B -> D transition and a convolution of a short distance
coefficient with the nonperturbative pion light-cone wave function. This is
shown to all orders in alpha_s, up to corrections suppressed by factors of
1/mb, 1/mc, and 1/E_pi. It is not necessary to assume that the pion state is
dominated by the q-qbar Fock state.Comment: 4 pages, 3 figs, PRL versio
Enhanced Direct CP Violation in
We study direct CP violation in the hadronic decay , including the effect of mixing. We find
that the CP violating asymmetry is strongly dependent on the CKM matrix
elements, especially the Wolfenstein parameter . For fixed (the
effective parameter associated with factorization), the CP violating asymmetry,
, has a maximum of order when the invariant mass of the
pair is in the vicinity of the resonance. The
sensitivity of the asymmetry, , to is small. Moreover, if is
constrained using the latest experimental branching ratios from the CLEO
collaboration, we find that the sign of is always positive. Thus,
a measurement of direct CP violation in would
remove the mod ambiguity in .Comment: 37 pages, 7 figure
CP violation in chargino production and decay into sneutrino
We study CP odd asymmetries in chargino production E+ E- --> ~Chi(+-)(1)
\~Chi(-+)(2) and the subsequent two-body decay of one chargino into a
sneutrino. We show that in the Minimal Supersymmetric Standard Model with
complex parameter \mu the asymmetries can reach 30 %. We discuss the
feasibility of measuring these asymmetries at a linear collider with \sqrt{s} =
800 GeV and longitudinally polarized beams.Comment: 10 pages, 3 figure
Stratigraphy of Lake Vida, Antarctica: hydrologic implications of 27 m of ice
Lake Vida, located in Victoria Valley, is one of the largest lakes in the
McMurdo dry valleys and is known to contain hypersaline liquid brine sealed
below 16 m of freshwater ice. For the first time, Lake Vida was drilled to a
depth of 27 m. Below 21 m the ice is marked by well-sorted sand layers up
to 20 cm thick within a matrix of salty ice. From ice chemistry, isotopic
composition of δ18O and δ2H, and ground penetrating radar
profiles, we conclude that the entire 27 m of ice formed from surface
runoff and the sediment layers represent the accumulation of surface
deposits. Radiocarbon and optically stimulated luminescence dating limit the
maximum age of the lower ice to 6300 14C yr BP. As the ice cover
ablated downwards during periods of low surface inflow, progressive
accumulation of sediment layers insulated and preserved the ice and brine
beneath, analogous to the processes that preserve shallow ground ice. The
repetition of these sediment layers reveals hydrologic variability in
Victoria Valley during the mid- to late Holocene. Lake Vida is an exemplar
site for understanding the preservation of subsurface brine, ice, and sediment
in a cold desert environment
Bounds on R-Parity Violating Parameters from Fermion EDM's
We study one-loop contributions to the fermion electric dipole moments in the
Minimal Supersymmetric Standard Model with explicit R-parity violating
interactions. We obtain new individual bounds on R-parity violating Yukawa
couplings and put more stringent limits on certain parameters than those
obtained previously.Comment: 16 pages, LaTe
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