1,431,922 research outputs found
Detailed L3 measurements of Bose-Einstein correlations and a region of anti-correlations in hadronic Z^0 decays at LEP
L3 preliminary data of two-particle Bose-Einstein correlations are reported
for hadronic Z^0 decays in e+e- annihilation at LEP. The invariant relative
momentum Q is identified as the eigenvariable of the measured correlation
function. Significant anti-correlations are observed in the Bose-Einstein
correlation function in a broad region of 0.5 - 1.6 GeV with a minimum at Q
close to 0.8 GeV. Absence of Bose-Einstein correlations is demonstrated in the
region above Q >= 1.6 GeV. The effective source size is found to decrease with
increasing value of the transverse mass of the pair, similarly to hadron-hadron
and heavy ion reactions. These feautes and our data are described well by the
non-thermal tau-model, which is based on strong space-time
momentum-correlations.Comment: 5 pages, 1 figure, invited talk at the XXXIXth International
Symposium on Multiparticle Dynamics, Gomel, Belarus, September 200
Photoproduction of Pentaquark in Feynman and Regge Theories
Photoproduction of the Theta+ pentaquark on the proton is analyzed by using
an isobar and a Regge models. The difference in the calculated total cross
section is found to be more than two orders of magnitude for a hadronic form
factor cut-off Lambda > 1 GeV. Comparable results would be obtained for 0.6 <
Lambda < 0.8 GeV. We also calculate contribution of the Theta+ photoproduction
to the GDH integral. By comparing with the current phenomenological
calculation, it is found that the GDH sum rule favors the result obtained from
Regge approach and isobar model with small Lambda.Comment: 5 pages, 5 figures, submitted to Phys.Rev.C as a Rapid Communicatio
Passenger ride quality response to an airborne simulator environment
The present study was done aboard a special aircraft able to effect translations through the center of gravity with a minimum of pitch and roll. The aircraft was driven through controlled motions by an on-board analog computer. The input signal was selectively filtered Gaussian noise whose power spectra approximated that of natural turbulence. This input, combined with the maneuvering capabilities of this aircraft, resulted in an extremely realistic simulation of turbulent flight. The test flights also included varying bank angles during turns. Subjects were chosen from among NASA Flight Research Center personnel. They were all volunteers, were given physical examinations, and were queried about their attitudes toward flying before final selection. In profile, they were representative of the general flying public. Data from this study include (1) a basis for comparison with previous commercial flights, that is, motion dominated by vertical acceleration, (2) extension to motion dominated by lateral acceleration, and (3) evaluation of various bank angles
Time Evolution In Macroscopic Systems. II: The Entropy
The concept of entropy in nonequilibrium macroscopic systems is investigated
in the light of an extended equation of motion for the density matrix obtained
in a previous study. It is found that a time-dependent information entropy can
be defined unambiguously, but it is the time derivative or entropy production
that governs ongoing processes in these systems. The differences in physical
interpretation and thermodynamic role of entropy in equilibrium and
nonequilibrium systems is emphasized and the observable aspects of entropy
production are noted. A basis for nonequilibrium thermodynamics is also
outlinedComment: 28 page
Laboratory studies of baroclinic instability at small Richardson number
As part of the support program for the Atmospheric General Circulation Experiment, laboratory studies of baroclinic and other convective instabilities were performed for a thin layer of fluid between thermally conducting horizontal discs. There were three types of modes identified. The first has a spiral-arm appearance, and exists for large enough horizontal thermal forcing, weak enough static stability, and large enough rotation. The source of this wave is shown to be the Eady mode of instability. The second mode is due to convective instability in the thermal boundary layers which exist due to the thermally conducting horizontal boundaries. Finally, for strong enough negative static stability, thermal convection of the Benard type appears. The most significant result is that the symmetric (Solberg) mode was not found, even though the infinite-plane theory predicts this mode under certain experimental conditions
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