4,671 research outputs found
Cyclotron resonance propulsion system semiannual report no. 1
Cyclotron resonance plasma accelerator for space propulsion application
Investigation of plasma accelerator /cyclotron resonance propulsion system/ Final report
Electron cyclotron resonance plasma accelerators for space propulsion system
Convergence properties of simple genetic algorithms
The essential parameters determining the behaviour of genetic algorithms were investigated. Computer runs were made while systematically varying the parameter values. Results based on the progress curves obtained from these runs are presented along with results based on the variability of the population as the run progresses
Quark-Gluon Jet Differences at LEP
A new method to identify the gluon jet in 3-jet ``{\bf Y}'' decays of
is presented. The method is based on differences in particle multiplicity
between quark jets and gluon jets, and is more effective than tagging by
leptonic decay. An experimental test of the method and its application to a
study of the ``string effect'' are proposed. Various jet-finding schemes for
3-jet events are compared.Comment: 11 pages, LaTeX, 4 PostScript figures availble from the author
([email protected]), MSUTH-92-0
Meaningful characterisation of perturbative theoretical uncertainties
We consider the problem of assigning a meaningful degree of belief to
uncertainty estimates of perturbative series. We analyse the assumptions which
are implicit in the conventional estimates made using renormalisation scale
variations. We then formulate a Bayesian model that, given equivalent initial
hypotheses, allows one to characterise a perturbative theoretical uncertainty
in a rigorous way in terms of a credibility interval for the remainder of the
series. We compare its outcome to the conventional uncertainty estimates in the
simple case of the calculation of QCD corrections to the e+e- -> hadrons
process. We find comparable results, but with important conceptual differences.
This work represents a first step in the direction of a more comprehensive and
rigorous handling of theoretical uncertainties in perturbative calculations
used in high energy phenomenology.Comment: 28 pages, 5 figures. Language modified in order to make it more
'bayesian'. No change in results. Version published in JHE
Measurement of the strong coupling alpha_S from the three-jet rate in e+e- - annihilation using JADE data
We present a measurement of the strong coupling alpha_S using the three-jet
rate measured with the Durham algorithm in e+e- -annihilation using data of the
JADE experiment at centre-of-mass energies between 14 and 44 GeV. Recent
theoretical improvements provide predictions of the three-jet rate in e+e-
-annihilation at next-to-next-to-leading order. In this paper a measurement of
the three-jet rate is used to determine the strong coupling alpha_s from a
comparison to next-to-next-to-leading order predictions matched with
next-to-leading logarithmic approximations and yields a value for the strong
coupling alpha_S(MZ) = 0.1199+- 0.0010 (stat.) +- 0.0021 (exp.) +- 0.0054
(had.) +- 0.0007 (theo.) consistent with the world average.Comment: 27 pages, 8 figure
Analytic Perturbation Theory for Practitioners and Upsilon Decay
Within the ghost-free Analytic Perturbation Theory (APT), devised in the last
decade for low energy QCD, simple approximations are proposed for 3-loop
analytic couplings and their effective powers, in both the space-like
(Euclidean) and time-like (Minkowskian) regions, accurate enough in the large
range (1--100 GeV) of current physical interest.\par Effectiveness of the new
Model is illustrated by the example of decay where the
standard analysis gives value that is
inconsistent with the bulk of data for .
Instead, we obtain that
corresponds to that is close to the world
average.\par The issue of scale uncertainty for decay is also
discussed.Comment: 12 pages, 0 figures. Model slightly modified to increase its
accuracy. Numerical results upgraded, references added. The issue of scale
uncertainty is discusse
Hints of New Flavor Physics at LEP?
A massive gauge boson coupling to the third family but not lighter families
mixes with the . The partial width to increases, the
asymmetry parameter increases, the invisible width of the decreases,
and decreases, all in a manner consistent with present data.Comment: 8 pages, LaTeX, UTPT-94-20. (Version to be published - some
discussion added.
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