27 research outputs found
Non-Relativistic QCD for Heavy Quark Systems
We employ a nonrelativistic version of QCD (NRQCD) to study heavy
quark-antiquark bound states in the lowest approximation without fine
structure. We use gluon configurations on a 16^3 by 48 lattice at beta=6.2 from
the UKQCD collaboration. For quark masses in the vicinity of the b we obtain
bound state masses for S, P and both types of D wave. We also detect signals
for two types of hybrids (quark,antiquark,gluon states). The results are
sufficiently accurate to confirm that the values of the D wave mass from both
lattice D waves coincide indicating that the cubical invariance of the lattice
is restored to full rotational invariance at large distance.
Our results also show that the S-P splitting is indeed insensitive to
variations in the bare quark mass from Ma=1.0 to Ma=1.9.Comment: 13 pages, DAMTP-92-7
Radial Excited States for Heavy Quark Systems in NRQCD
Following the Non-Relativistic QCD approach we use a gauge invariant smearing
method with factorization to measure the excitation energies for a heavy
system on a lattice at . The results come
from averaging over an ensemble of 60 QCD configurations. In order to enhance
the signal from each configuration we use wall sources for quark propagators.
The quark Hamiltonian contains only the simplest non-relativistic kinetic
energy term. The results are listed for a range of bare quark masses. The mass
splittings are insensitive to this variable though there are a slight trends
with increasing quark mass. For an appropriate choice of UV cut-off
(Gev) the mass spectrum compares reasonably well with the
experimental values for the spin-averaged energy gaps of the system.
We also present results for the and waves for the lowest bare quark
mass. The results are consistent with degeneracy between the two types of
wave. This encourages the idea that even with our simple quark Hamiltonian the
departure from rotational invariance is not great.Comment: 12 page
NEOTROPICAL XENARTHRANS: a data set of occurrence of xenarthran species in the Neotropics
Xenarthrans – anteaters, sloths, and armadillos – have essential functions for ecosystem maintenance, such as insect control and nutrient cycling, playing key roles as ecosystem engineers. Because of habitat loss and fragmentation, hunting pressure, and conflicts with 24 domestic dogs, these species have been threatened locally, regionally, or even across their full distribution ranges. The Neotropics harbor 21 species of armadillos, ten anteaters, and six sloths. Our dataset includes the families Chlamyphoridae (13), Dasypodidae (7), Myrmecophagidae (3), Bradypodidae (4), and Megalonychidae (2). We have no occurrence data on Dasypus pilosus (Dasypodidae). Regarding Cyclopedidae, until recently, only one species was recognized, but new genetic studies have revealed that the group is represented by seven species. In this data-paper, we compiled a total of 42,528 records of 31 species, represented by occurrence and quantitative data, totaling 24,847 unique georeferenced records. The geographic range is from the south of the USA, Mexico, and Caribbean countries at the northern portion of the Neotropics, to its austral distribution in Argentina, Paraguay, Chile, and Uruguay. Regarding anteaters, Myrmecophaga tridactyla has the most records (n=5,941), and Cyclopes sp. has the fewest (n=240). The armadillo species with the most data is Dasypus novemcinctus (n=11,588), and the least recorded for Calyptophractus retusus (n=33). With regards to sloth species, Bradypus variegatus has the most records (n=962), and Bradypus pygmaeus has the fewest (n=12). Our main objective with Neotropical Xenarthrans is to make occurrence and quantitative data available to facilitate more ecological research, particularly if we integrate the xenarthran data with other datasets of Neotropical Series which will become available very soon (i.e. Neotropical Carnivores, Neotropical Invasive Mammals, and Neotropical Hunters and Dogs). Therefore, studies on trophic cascades, hunting pressure, habitat loss, fragmentation effects, species invasion, and climate change effects will be possible with the Neotropical Xenarthrans dataset
Physics of heavy quarks
SIGLEAvailable from British Library Document Supply Centre-DSC:D063664 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
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