745 research outputs found
The charm quark mass with dynamical fermions
We compute the charm quark mass in lattice QCD and compare different
formulations of the heavy quark, and quenched data to that with dynamical sea
quarks. We take the continuum limit of the quenched data by extrapolating from
three different lattice spacings, and compare to data with two flavours of
dynamical sea quarks with a mass around the strange at the coarsest lattice
spacing. Both the FNAL and ALPHA formalism are used. We find the different
heavy quark formulations have the same continuum limit in the quenched
approximation, and limited evidence that this approximation overestimates the
charm quark mass.Comment: Lattice2004(heavy) 3 pages, 2 figure
The effect of sea quarks on the mass of the charm quark from Lattice QCD
We compute the mass of the charm quark using both quenched and dynamical
lattice QCD calculations. We examine the effects of mass dependent lattice
artifacts by comparing two different formalisms for the heavy quarks. We take
the continuum limit of the charm mass in quenched QCD by extrapolating from
three different lattice spacings. At a fixed lattice spacing, the mass of the
charm quark is compared between quenched QCD and dynamical QCD with a sea quark
mass around strange. In the continuum limit of quenched QCD, we find
m_c(m_c)=1.29(7)(13) GeV. No evidence was seen for unquenching.Comment: Added NP analysis of quenched data, corrected error in PCAC RGI mass,
updated strange quark mass discussion and references, unified notation and
corrected typos. No change in final result. Version accepted for publication
in JHE
The mass of the charm quark from unquenched lattice QCD at fixed lattice spacing
We determine the mass of the charm quark () from lattice QCD with two
flavors of dynamical quarks with a mass around the strange quark. We compare
this to a determination in quenched QCD which has the same lattice spacing (0.1
fm). We investigate different formulations of the quark mass, based on the
Vector Ward Identity, PCAC relation and the FNAL heavy quark formalism. Based
on these preliminary results we find no effects due to sea quarks with a mass
around strange.Comment: Presented at 21st International Symposium on Lattice Field Theory
(LATTICE 2003), Tsukuba, Japan, 15-19 July, 200
Staggered Chiral Perturbation Theory for Heavy-Light Mesons
We incorporate heavy-light mesons into staggered chiral perturbation theory,
working to leading order in 1/m_Q, where m_Q is the heavy quark mass. At first
non-trivial order in the chiral expansion, staggered taste violations affect
the chiral logarithms for heavy-light quantities only through the light meson
propagators in loops. There are also new analytic contributions coming from
additional terms in the Lagrangian involving heavy-light and light mesons.
Using this heavy-light staggered chiral perturbation theory, we perform the
one-loop calculation of the B (or D) meson leptonic decay constant in the
partially quenched and full QCD cases. In our treatment, we assume the validity
both of the "fourth root trick" to reduce four staggered tastes to one, and of
the prescription to represent this trick in the chiral theory by insertions of
factors of 1/4 for each sea quark loop.Comment: 48 pages, 6 figures. v3: Some clarifying comments/caveats added;
typos fixed. Corresponds to published versio
The heavy quark's self energy from moving NRQCD on the lattice
We present a calculation of the heavy quark's self energy in moving NRQCD to
one-loop in perturbation theory. Results for the energy shift and external
momentum renormalisation are discussed and compared with non-perturbative
results. We show that the momentum renormalisation is small, which is the
result of a remnant of re-parameterisation invariance on the lattice.Comment: Talk given at Lattice2004(heavy), Fermilab, June 21-26, 200
Charm and Bottom Quark Masses from Perturbative QCD
Using a new result for the first moment of the hadronic production cross
section at order , and new data on the and
resonances for the charm quark, we determine the \msb masses of the
charm and bottom quarks to be GeV and
GeV. We assume that the continuum
contribution to the sum rules is adequately described by pQCD. While we observe
a large reduction of the perturbative error, the shifts induced by the
theoretical input are very small. The main change in the central value of
is related to the experimental data. On the other hand, the value of is
not changed by our calculation to the assumed precision.Comment: 5 pages, 2 figures, final version as publishe
The second moment of the pion's distribution amplitude
We present preliminary results for the second moment of the pion's
distribution amplitude. The lattice formulation and the phenomenological
implications are briefly reviewed, with special emphasis on some subtleties
that arise when the Lorentz group is replaced by the hypercubic group. Having
analysed more than half of the available configurations, the result obtained is
\xi^2_L = 0.06 \pm 0.02.Comment: Lattice 99 (matrix elements), 3 page
Analytic solutions of a simple advection-diffusion model of an oxygen transfer device
Artificial blood oxygenation is an essential aspect of cardiopulmonary bypass surgery, maintaining physiological levels of oxygen and carbon dioxide in the blood, and thus temporarily replacing the normal function of the lungs. The blood-gas exchange devices used for such procedures have a long history and have had varying degrees of success. In this paper we consider a simple model of a new approach to enhancing the diffusion of oxygen into the blood while it is contained in the artificial blood oxygenator. We show that using a transverse flow, which may be set up using mixing elements that we have previously shown experimentally to enhance blood oxygenation, will increase the oxygen levels within the blood. This simple model and associated analytic solutions can then be used to aid the optimisation of blood oxygenation devices
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