Search results for " Likelihood"

Penalized inference in multivariate ordered logistic models: theory and applications

2010

User participation in knowledge update of expert systems

1997

Abstract Applying the Elaboration Likelihood Model (ELM) of persuasion we conducted an experiment to examine the effect of participation of users in the design process on their acceptance of system recommendations and revision of their original decisions. Results of our study indicate that two different types of information processing occur when subjects are reviewing the expert system recommendations. 1. (i) For users who have a high perceived level of participation in updating the knowledge of the ES, ambiguity of the decision setting is the primary determinant affecting acceptance of the recommendation from the ES. 2. (ii) For users who have a low perceived level of participation in upda…

A Robust Determination of the size of quasar accretion disks using gravitational microlensing

2012

Using microlensing measurements from a sample of 27 image-pairs of 19 lensed quasars we determine a maximum likelihood estimate for the accretion disk size of an {{\em}average} quasar of $r_s=4.0^{+2.4}_{-3.1} $ light days at rest frame $=1736$\AA\ for microlenses with a mean mass of $=0.3M_\odot$. This value, in good agreement with previous results from smaller samples, is roughly a factor of 5 greater than the predictions of the standard thin disk model. The individual size estimates for the 19 quasars in our sample are also in excellent agreement with the results of the joint maximum likelihood analysis.

Approches région et bayésienne pour la restauration ďimages dégradées par la turbulence atmosphérique

2001

La turbulence atmospherique perturbe ľobservation a haute resolution. C’est un phenomene etudie depuis longtemps, en astronomie notamment. Le present article porte sur le cas de ľobservation ďun objet situe environ vingt kilometres, la propagation etant horizontale et pres du sol, en infrarouge. Les images a longue pose sont restaurees avec des algorithmes classiques de deconvolution. Les resultats ne sont satisfaisants que pour une faible perturbation. Il est plus avantageux ďexploiter des images courte pose, car elles contiennent plus de hautes frequences spatiales; mais ľobjet observe y fluctue aleatoirement. On travaille donc ici partir ďune sequence de plusieurs dizaines ďimages. Deux …

Measurements of neutralBdecay branching fractions toKS0π+π−final states and the charge asymmetry ofB0→K*+π−

2006

Branching fraction measurements using B-meson decays to Kspi+pi- are presented. These measurements were obtained by analyzing a data sample of 88.9 million Y(4S) --> BB decays collected with the BaBar detector at the SLAC PEP-II asymmetric-energy B factory. Using a maximum likelihood fit, the following branching fraction results were obtained: Br(B0 -> K0pi+pi- = (43.7 +/- 3.8 +/- 3.4) * 10^-6, Br(B0 --> K{*+}pi-) = (12.9 +/- 2.4 +/- 1.4) * 10$^-6} and Br(B0 --> D-(--> Kspi-)pi+ = (42.7 +/- 2.1 +/- 2.2) * 10^{-6}. The CP violating char ge asymmetry A(K*pi} for the decay B0 --> $K{*+}pi-$ was measured to be A(K*pi} = 0.23 +/- $0.18^{+0.09}_{-0.06}$. For all these measurements the first error…

Searching for localized cosmic particle sources with an unbinned maximum likelihood approach

2006

Abstract An unbinned method to search for localized cosmic particle sources is presented. The expected source shape, the measured background shape, and the estimated angular resolution of individual tracks are used to construct a likelihood function. Estimates of the flux, the position and—in particular—the significance of a source can be readily obtained. A full confidence belt construction to deduce flux limits is presented. General statistical issues when searching for sources of unknown position are discussed.

Precision measurement of the mass of the tau lepton

2014

An energy scan near the $\tau$ pair production threshold has been performed using the BESIII detector. About $24$ pb$^{-1}$ of data, distributed over four scan points, was collected. This analysis is based on $\tau$ pair decays to $ee$, $e\mu$, $eh$, $\mu\mu$, $\mu h$, $hh$, $e\rho$, $\mu\rho$ and $\pi\rho$ final states, where $h$ denotes a charged $\pi$ or $K$. The mass of the $\tau$ lepton is measured from a maximum likelihood fit to the $\tau$ pair production cross section data to be $m_{\tau} = (1776.91\pm0.12 ^{+0.10}_{-0.13}$) MeV/$c^2$, which is currently the most precise value in a single measurement.

The EM imaging reconstruction method in γ-ray astronomy

1998

Abstract The simpler imaging reconstruction methods used for γ-ray coded mask telescopes are based on correlation methods, very fast and simple-to-use but with limitations in the reconstructed image. To improve these results, other reconstruction methods have been developed, such as the maximum entropy methods or the Iterative Removal Of Sources (IROS). However, such kind of methods are slower and can be impracticable for very complex telescopes. In this paper we present an alternative image reconstruction method, based on an iterative maximum likelihood algorithm called the EM algorithm, easy to implement and that can be successfully used for not very complex coded mask systems, as is the …

Modelling of Magnetic Resonance Spectra Using Mixtures for Binned and Truncated Data

2007

Magnetic Resonance Spectroscopy (MRS) provides the biochemical composition of a tissue under study. This information is useful for the in-vivo diagnosis of brain tumours. Prior knowledge of the relative position of the organic compound contributions in the MRS suggests the development of a probabilistic mixture model and its EM-based Maximum Likelihood Estimation for binned and truncated data. Experiments for characterizing and classifying Short Time Echo (STE) spectra from brain tumours are reported.

Measurements of the Branching Fraction andCP-Violation Asymmetries inB0→f0(980)KS0

2005

The authors present measurements of the branching fraction and CP-violating asymmetries in the decay B{sup 0} {yields} f{sub 0}(980)K{sub S}{sup 0}. The results are obtained from a data sample of 123 x 10{sup 6} {Upsilon}(4S) {yields} B{bar B} decays. From a time-dependent maximum likelihood fit they measure the branching fraction {Beta}(B{sup 0} {yields} f{sub 0}(980)({yields}{Pi}{sup +}{pi}{sup 0})K{sup 0}) = (6.0 {+-} 0.9 {+-} 0.6 {+-} 1.2) x 10{sup -6}, the mixing-induced CP violation parameter S = 1.62{sub -0.51}{sup +0.56} {+-} 0.09 {+-} 0.04 and the direct CP violation parameter C = 0.27 {+-} 0.36 {+-} 0.10 {+-} 0.07, where the first errors are statistical, the second systematic and …