6,095 research outputs found
On the survival probability of a random walk in random environment with killing
We consider one dimensional random walks in random environment where every
time the process stays at a location, it dies with a fixed probability. Under
some mild assumptions it is easy to show that the survival probability goes to
zero as time tends to infinity. In this paper we derive formulas for the rate
with which this probability decays. It turns out that there are three distinct
regimes, depending on the law of the environment
Confidence Level Computation for Combining Searches with Small Statistics
This article describes an efficient procedure for computing approximate
confidence levels for searches for new particles where the expected signal and
background levels are small enough to require the use of Poisson statistics.
The results of many independent searches for the same particle may be combined
easily, regardless of the discriminating variables which may be measured for
the candidate events. The effects of systematic uncertainty in the signal and
background models are incorporated in the confidence levels. The procedure
described allows efficient computation of expected confidence levels.Comment: 17 pages, 2 figures, LaTeX, program available at
http://home.cern.ch/~thomasj/searchlimits/ecl.html one replacement to fix a
typo in a UR
Recent Heavy-Flavor Measurements from OPAL
A selection of recent heavy-flavor results from OPAL using the LEP1 data
sample are presented. The average polarization of b baryons in hadronic Z^0
decay has been measured to be -0.56^{+0.20}_{-0.13} (stat.) +- 0.09(syst.)
using semileptonic decays of Lambda_b baryons. A search has been conducted for
the radially excited D*' and has produced a 95% CL upper limit on its
production of f(Z^0 -> D*'+-(2629))xBr(D*'+- -> D*+- pi+ pi-) < 2.1x10^{-3}.
Finally, the measurement of the product branching ratio $f(b ->
Lambda_b)xBr(Lambda_b -> Lambda X)= (2.67 +- 0.38 (stat)
^{+0.67}_{-0.60}(syst.))% has been made. This measurement, along with an
earlier measurement of the product branching ratio f(b -> Lambda_b)xBr(Lambda_b
-> Lambda l X), has been used to compute an updated R_{Lambda l} = Br(Lambda_b
-> Lambda l X)/Br(Lambda_b -> \Lambda X)= (8.0 +- 1.2 (stat.) +- 0.9 (syst.))%,
consistent with the expected low semileptonic branching fraction of the
Lambda_b inferred from its short lifetime compared to the other b hadrons.Comment: 9 Pages, LaTeX, 4 figures. Proceedings contributed to DPF'99, UCLA,
Parallel session talk 3.0
A Lifting Relation from Macroscopic Variables to Mesoscopic Variables in Lattice Boltzmann Method: Derivation, Numerical Assessments and Coupling Computations Validation
In this paper, analytic relations between the macroscopic variables and the
mesoscopic variables are derived for lattice Boltzmann methods (LBM). The
analytic relations are achieved by two different methods for the exchange from
velocity fields of finite-type methods to the single particle distribution
functions of LBM. The numerical errors of reconstructing the single particle
distribution functions and the non-equilibrium distribution function by
macroscopic fields are investigated. Results show that their accuracy is better
than the existing ones. The proposed reconstruction operator has been used to
implement the coupling computations of LBM and macro-numerical methods of FVM.
The lid-driven cavity flow is chosen to carry out the coupling computations
based on the numerical strategies of domain decomposition methods (DDM). The
numerical results show that the proposed lifting relations are accurate and
robust
Sedimentological studies of the "Ilha de Marchantaria" in the Solimões/Amazon River near Manaus
Sedimentological studies on the Ilha de Marchantaria an island in the Amazon river near Manaus reveal the existence of four different structural main units. A: Sandy channel bars consisting of giant ripples constitute deposits for the formation of islands or newly formed areas of the Varzea. B: Gradual accumulation on the channel bars leads to the formation of point bar ridges which consist chiefly of small-scale ripples. C: Between point bar ridges of different ages there exist swales. During rising water level the river water flows from the downward side into the swales where finegrained sediments are deposited. D: Permanent lakes are formed mainly in the centre of the islands. During low water periods the lakes may be cut of from the river. During high water periods when the whole island is flooded by the river, additional sedimentation takes place especially in the upstream area of the island. There is however, extensive erosion of the banks on the upstream side of the island. By erosion of the upstream end and sedimentation processes on the downstream end the island moves slowly downstream
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