6,960 research outputs found
Semi-leptonic decays heavy-light to heavy light
We present results for the QCD matrix elements involved in semi-leptonic
decays of B-mesons into pseudo scalar heavy light states. The application of
NRQCD heavy quarks allows for quark masses around the physical b-quark. We
investigate the dependence of the form factors on the external momenta and
looked at the mass dependence at zero recoil. For the first time, results for
radially excited decay products are presented.Comment: 3 pages LaTeX, 5 figures, Talk given at LATTICE99(Heavy Quarks), June
29th to July 3rd, 1999, Pisa, Ital
Ultrasound by emergency physicians to detect abdominal aortic aneurysms: a UK case series
Early identification of abdominal aortic aneurysms in some
patients can be difficult and the diagnosis is missed in up to
30% of patients. Ultrasound cannot be used to identify a leak,
but the presence of an aneurysm in an unstable patient is
conclusive. With minimal training emergency physicians can
easily identify the aorta and thus in the early phase of
resuscitation an aneurysm can be confidently excluded. The
purpose of the examination is not to delineate the extent of
the aneurysm, but to identify those patients that will need
emergency surgery. A series of patients presented to the
department in an unstable condition with equivocal abdominal
signs. An ultrasound scan in the resuscitation room by
members of the emergency department revealed an aneurysm,
which was enough to convince the vascular surgeons to
take the patient straight to theatre with good results. In
patients who are stable, computed tomography will continue
to be used to evaluate the extent of the aneurysm and identify a leak
Force and energy dissipation variations in non-contact atomic force spectroscopy on composite carbon nanotube systems
UHV dynamic force and energy dissipation spectroscopy in non-contact atomic
force microscopy were used to probe specific interactions with composite
systems formed by encapsulating inorganic compounds inside single-walled carbon
nanotubes. It is found that forces due to nano-scale van der Waals interaction
can be made to decrease by combining an Ag core and a carbon nanotube shell in
the Ag@SWNT system. This specific behaviour was attributed to a significantly
different effective dielectric function compared to the individual
constituents, evaluated using a simple core-shell optical model. Energy
dissipation measurements showed that by filling dissipation increases,
explained here by softening of C-C bonds resulting in a more deformable
nanotube cage. Thus, filled and unfilled nanotubes can be discriminated based
on force and dissipation measurements. These findings have two different
implications for potential applications: tuning the effective optical
properties and tuning the interaction force for molecular absorption by
appropriately choosing the filling with respect to the nanotube.Comment: 22 pages, 6 figure
Scaling and Further Tests of Heavy Meson Decay Constant Determinations from Nonrelativistic QCD
We present results for the B_s meson decay constant f_{B_s} from simulations
at three lattice spacings in the range a^{-1}=1.1 to 2.6 GeV using NRQCD heavy
quarks and clover light quarks in the quenched approximation. We study scaling
of this quantity and check the consistency between mesons decaying from rest
and from a state with nonzero spatial momentum. The cancellation of power law
contributions that arise in the NRQCD formulation of heavy-light currents is
discussed. On the coarsest lattice the D_s meson decay constant f_{D_s} is
calculated. Our best values for the decay constants are given by f_{B_s} =
187(4)(4)(11)(2)(7)(6) MeV and f_{D_s} = 223(6)(31)(38)(23)(9)(^{+3}_{-1}) MeV.Comment: 29 pages with 7 postscript figures, improved error analysis, version
to appear in Physical Review
New results on heavy hadron spectroscopy with NRQCD
We present results for the spectrum of b-bbar bound states in the quenched
approximation for three different values of the lattice spacing. Results for
spin-independent splittings are shown to have good scaling behaviour;
spin-dependent splittings are more sensitive to discretisation effects. We
discuss what needs to be done to match the experimental spectrum.Comment: 3 pages, contribution to Lattice'9
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