44,959 research outputs found
Contribution of through the QCD anomaly in exclusive decays and
We compute the decay rates for the exclusive decays and in a QCD-improved factorization framework by including the
contribution from the process through
the QCD anomaly. This method provides an alternative estimate of the
contribution to these decays as
compared to the one using the intrinsic charm content of the
and mesons determined through the decays . The resulting branching ratios are compared with the CLEO
data on and
and predictions are made for the rest.Comment: 16 pages including 4 postscript figures; uses epsfig. The most recent
branching ratios from CLEO, ref. [5], are taken into account. The theory part
is unchange
B Physics with NRQCD: A Quenched Study
We present results on the spectrum of B mesons and heavy baryons, using a
non-relativistic formulation for the heavy and a clover action for the light
quark. We also discuss B meson decay constants and their dependency upon the
heavy meson mass.Comment: 4 pages, uuencoded compressed postscript file, contribution to
LATTICE 9
Controlled enhancement or suppression of exchange biasing using impurity -layers
The effects of inserting impurity -layers of various elements into a
Co/IrMn exchange biased bilayer, at both the interface, and at given points
within the IrMn layer a distance from the interface, has been investigated.
Depending on the chemical species of dopant, and its position, we found that
the exchange biasing can be either strongly enhanced or suppressed. We show
that biasing is enhanced with a dusting of certain magnetic impurities, present
at either at the interface or sufficiently far away from the Co/IrMn interface.
This illustrates that the final spin structure at the Co/IrMn interface is not
only governed by interface structure/roughness but is also mediated by local
exchange or anisotropy variations within the bulk of the IrMn
External Momentum, Volume Effects, and the Nucleon Magnetic Moment
We analyze the determination of volume effects for correlation functions that
depend on an external momentum. As a specific example, we consider finite
volume nucleon current correlators, and focus on the nucleon magnetic moment.
Because the multipole decomposition relies on SO(3) rotational invariance, the
structure of such finite volume corrections is unrelated to infinite volume
multipole form factors. One can deduce volume corrections to the magnetic
moment only when a zero-mode photon coupling vanishes, as occurs at
next-to-leading order in heavy baryon chiral perturbation theory. To deduce
such finite volume corrections, however, one must assume continuous momentum
transfer. In practice, volume corrections with momentum transfer dependence are
required to address the extraction of the magnetic moment, or other observables
that arise in momentum dependent correlation functions. Additionally we shed
some light on a puzzle concerning differences in lattice form factor data at
equal values of momentum transfer squared.Comment: 21 pages, 5 figures; discussion in Sect. IV C expanded, Figs. now B&W
friendl
Issues on the molecular-beam epitaxial growth of p-SiGe inverted-modulation-doped structures
The influence of boron segregation and silicon cap-layer thickness on two-dimensional hole gases (2-DHGs) has been investigated in Si/Si0.8Ge0.2/Si inverted-modulation-doped heterostructures grown by solid-source molecular-beam epitaxy. Boron segregation, which is significant in structures with small spacer layers, can be suppressed by growth interruption after the boron doping. How growth interruption affected the electrical properties of the 2-DHG and the boron doping profile as measured by secondary ion mass spectroscopy are reported. We report also on the role played by the unpassivated silicon cap, and compare carrier transport at the normal and inverted interfaces
Heavy-light meson decay constants from NRQCD: an analysis of the 1/M corrections
We present {\it preliminary} results for the decay constants of heavy-light
mesons using NRQCD heavy and tadpole improved Clover light quarks. A comparison
is made with data obtained using Wilson light quarks. We present an analysis of
the 1/M corrections to the decay constants in the static limit and compare with
the predictions of HQET.Comment: Contribution to Lattice 95, 4 pages uuencoded compressed postscript
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