30,669 research outputs found
Spectroscopic parameters and rest frequencies of isotopic methylidynium, CH+
Astronomical observations toward Sagittarius B2(M) as well as other sources
with APEX have recently suggested that the rest frequency of the J = 1 - 0
transitions of 13CH+ is too low by about 80 MHz. Improved rest frequencies of
isotopologs of methylidynium should be derived to support analyses of spectral
recording obtained with the ongoing Herschel mission or the upcoming SOFIA.
Laboratory electronic spectra of four isotopologs of CH+ have been subjected to
one global least-squares fit. Laboratory data for the J = 1 - 0 ground state
rotational transitions of CH+, 13CH+, and CD+, which became available during
the refereeing process, have been included in the fit as well. An accurate set
of spectroscopic parameters has been obtained together with equilibrium bond
lengths and accurate rest frequencies for six CH+ isotopologs: CH+, 13CH+,
13CD+, CD+, 14CH+, and CT+. The present data will be useful for the analyses of
or SOFIA observations of methylidynium isotopic species.Comment: Astronomy and Astrophysics, accepted as Letter; 4 (here 5) page
Domain wall dynamics in a two-component Bose-Mott insulator
We model the dynamics of two species of bosonic atoms trapped in an optical
lattice within the Mott regime by mapping the system onto a spin model. A field
gradient breaks the cloud into two domains. We study how the domain wall
evolves under adiabatic and diabatic changes of this gradient. We determine the
timescales for adiabaticity, and study how temperature evolves for slow ramps.
We show that after large, sudden changes of the field gradient, the system does
not equilibrate on typical experimental timescales. We find interesting spin
dynamics even when the initial temperature is large compared to the
super-exchange energy. We discuss the implication of our results for
experiments wishing to use such a two-component system for thermometry, or as
part of a cooling scheme.Comment: 6 pages, 5 figures Minor typographical errors corrected. Figure
labels changed. Added concluding statement
Fully double-logarithm-resummed cross sections
We calculate the complete double logarithmic contribution to cross sections
for semi-inclusive hadron production in the modified minimal-subtraction scheme
by applying dimensional regularization to the double logarithm approximation.
The full double logarithmic contribution to the coefficient functions for
inclusive hadron production in electron-positron annihilation is obtained in
this scheme for the first time. Our result agrees with all fixed order results
in the literature, which extend to next-next-to-leading order.Comment: To appear in Nuclear Physics
Classifying LEP Data with Support Vector Algorithms
We have studied the application of different classification algorithms in the
analysis of simulated high energy physics data. Whereas Neural Network
algorithms have become a standard tool for data analysis, the performance of
other classifiers such as Support Vector Machines has not yet been tested in
this environment. We chose two different problems to compare the performance of
a Support Vector Machine and a Neural Net trained with back-propagation:
tagging events of the type e+e- -> ccbar and the identification of muons
produced in multihadronic e+e- annihilation events.Comment: 7 pages, 4 figures, submitted to proceedings of AIHENP99, Crete,
April 199
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