123,639 research outputs found
Can lattice data for two heavy-light mesons be understood in terms of simply two-quark potentials?
By comparing lattice data for the two heavy-light meson system (Q^2 qbar^2)
with a standard many-body approach employing only interquark potentials, it is
shown that the use of unmodified two-quark potentials leads to a gross
overestimate of the binding energy.Comment: Contribution to LATTICE99 (Heavy Quarks). 3 pages, 2 ps figure
Searches for Compositeness at the Tevatron
Quark-quark and quark-lepton searches for compositenss at the Fermilab
Tevatron are summarized. These are of the contact-interaction variety where
sqrt(s-hat) < the hypothesized mass scales, Lambda. Tevatron experiments limit
a variety of compositeness phenomena in the range from 1.9 to 8.3 TeV. These
limits result from measurements of: the Ht spectrum (D0), dijet mass (D0),
dijet angular distribution (CDF, D0), drell-yan production (CDF, D0), and the
Neutral Current to Charged Current ratio (CCFR/NuTeV).Comment: Presented at VIIIth RENCONTRES DE BLOIS, with recent updates added. 7
Figure
Introduction to finite mixtures
Mixture models have been around for over 150 years, as an intuitively simple
and practical tool for enriching the collection of probability distributions
available for modelling data. In this chapter we describe the basic ideas of
the subject, present several alternative representations and perspectives on
these models, and discuss some of the elements of inference about the unknowns
in the models. Our focus is on the simplest set-up, of finite mixture models,
but we discuss also how various simplifying assumptions can be relaxed to
generate the rich landscape of modelling and inference ideas traversed in the
rest of this book.Comment: 14 pages, 7 figures, A chapter prepared for the forthcoming Handbook
of Mixture Analysis. V2 corrects a small but important typographical error,
and makes other minor edits; V3 makes further minor corrections and updates
following review; V4 corrects algorithmic details in sec 4.1 and 4.2, and
removes typo
An example of scaling MST Doppler spectra using median spectra, spectral smoothing, and velocity tracing
Although automatic, computer scaling methods appeared at the start of the MST (mesosphere stratosphere troposphere) radar technique, there is a continuing need for scaling algorithms that perform editing functions and increase the sensitivity of radar by post processing. The scaling method presented is an adaptation of the method of scaling MST Doppler spectra presented by Rastogi (1984). A brief overview of this method is as follows: a median spectrum is calculated from several sequential spectra; the median noise value is subtracted from this derived spectrum; the median spectrum is smoothed; the detection/nondetection decision is made by comparing the smoothed spectrum to the variance of the smoothed noise; and if a signal is detected, then the half-power points of the smoothed echo spectrum are used to place limits on the evaluation of the first two moments of the unsmoothed median spectrum. In all of the above steps, the algorithm is guided by tracing the expected velocity range upward from the lowest range as far as possible. The method is discussed in more detail
The essential ideal is a Cohen-Macaulay module
Let G be a finite p-group which does not contain a rank two elementary
abelian p-group as a direct factor. Then the ideal of essential classes in the
mod-p cohomology ring of G is a Cohen-Macaulay module whose Krull dimension is
the p-rank of the centre of G. This basically answers in the affirmative a
question posed by J. F. Carlson.Comment: 6 page
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