3,581 research outputs found
Mecidea longula Stål (Heteroptera: Pentatomidae: Pentatominae: Mecideini) is established in south Florida
A Caribbean species of Mecidea Dallas, M. longula Stål, apparently established in south Florida, is reported from the United States for the first time. Specimens were first collected in February 2008 in a light trap operated in Miami-Dade County, Florida. Collections in that trap have continued through the present. Searches near the trap location resulted in several specimens being taken from smutgrass, Sporobolus indicus (L.), an exotic grass now established throughout much of the southeastern United States. The three North American species of Mecidea are keyed and illustrated. In addition to the Florida locality, M. longula is reported for the first time from the British Virgin Islands, St. Kitts, St. Martin, and the Turks and Caicos Islands
A Comprehensive Study of the Radiative Decays of and to Pseudoscalar Meson Pairs, and Search for Glueballs
Using 53 pb of annihilation data taken at
GeV, a comprehensive study has been made of the radiative decays of samples of
5.1 million and 24.5 million into pairs of pseudoscalar
mesons, , , , , and .
Product branching fractions for the radiative decays of and
to scalar resonances , and tensor
resonances have been determined, and are
discussed in relation to predicted glueballs. For radiative decays
the search for glueballs has been extended to masses between 2.5 GeV and 3.3
GeV.Comment: 21 pages, 14 figures, published in PR
First Measurement of the Electromagnetic Form Factor of the Neutral Kaon at a Large Momentum Transfer and the Effect of Breaking
At large momentum transfers the photon interacts with the charges and spins
of the constituent partons in a hadron. It is expected that the neutral kaon
can acquire finite electromagnetic form factors because its wave function is
affected by the order of magnitude difference between the mass of the strange
quark and that of the down quark, or flavor breaking. We report on the
first measurement of the form factor of neutral kaons at the large timelike
momentum transfer of GeV by measuring the cross section for
at GeV using CLEO-c data with an integrated
luminosity of 586 pb. We obtain
, with a 90% C.L. interval of
. This is nearly an order of magnitude smaller than
, and indicates that the
effect of breaking is small. In turn, this makes it unlikely that the
recently observed strong violation of the pQCD prediction,
, which is based on the
assumption of similar wave functions for the pions and kaons, can be attributed
to breaking alone.Comment: 4 pages, 2 figures, accepted to PL
Diagrammatic perturbation theory and the pseudogap
We study a model of quasiparticles on a two-dimensional square lattice
coupled to Gaussian distributed dynamical fields. The model describes
quasiparticles coupled to spin or charge fluctuations and is solved by a Monte
Carlo sampling of the molecular field distributions. The non-perturbative
solution is compared to various approximations based on diagrammatic
perturbation theory. When the molecular field correlations are sufficiently
weak, the diagrammatic calculations capture the qualitative aspects of the
quasiparticle spectrum. For a range of model parameters near the magnetic
boundary, we find that the quasiparticle spectrum is qualitatively different
from that of a Fermi liquid in that it shows a double peak structure, and that
the diagrammatic approximations we consider fail to reproduce, even
qualitatively, the results of the Monte Carlo calculations. This suggests that
the pseudogap induced by a coupling to antiferromagnetic fluctuations and the
spin-splitting of the quasiparticle peak induced by a coupling to ferromagnetic
spin-fluctuations lie beyond diagrammatic perturbation theory
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