849 research outputs found
Momentum-dependence of charmonium spectral functions from lattice QCD
We compute correlators and spectral functions for J/psi and eta_c mesons at
nonzero momentum on anisotropic lattices with Nf=2. We find no evidence of
significant momentum dependence at the current level of precision. In the
pseudoscalar channel, the ground state appears to survive up to T~450MeV or
2.1T_c. In the vector channel, medium modifications may occur at lower
temperatures.Comment: 5 pages, 12 figure
The spectrum of radial, orbital and gluonic excitations of charmonium
We present results for the charmonium spectrum from dynamical QCD
simulations on anisotropic lattices. Using all-to-all
propagators we determine the ground and excited states of S, P and D waves and
hybrids. We also evaluate the disconnected (OZI suppressed) contribution to the
and Comment: 6 pages, 3 figures, Presented at 24th International Symposium on
Lattice Field Theory (Lattice 2006), Tucson, Arizona, 23-28 Jul 200
Accurate Checks of Universality for Dyson's Hierarchical Model
Using recently developed methods, we perform high-accuracy calculations of
the susceptibility near beta_c for the D=3 version of Dyson's hierarchical
model. Using linear fits, we estimate the leading gamma and subleading Delta
exponents. Independent estimates are obtained by calculating the first two
eigenvalues of the linearized renormalization group transformation. We found
gamma = 1.29914073 (with an estimated error of 10^{-8}) and, Delta=0.4259469
(with an estimated error of 10^{-7}) independently of the choice of local
integration measure (Ising or Landau-Ginzburg). After a suitable rescaling, the
approximate fixed points for a large class of local measure coincide accurately
with a fixed point constructed by Koch and Wittwer.Comment: 9 pages, Revtex, 1 figur
Numerical Tests of the Improved Fermilab Action
Recently, the Fermilab heavy-quark action was extended to include
dimension-six and -seven operators in order to reduce the discretization
errors. In this talk, we present results of the first numerical simulations
with this action (the OK action), where we study the masses of the quarkonium
and heavy-light systems. We calculate combinations of masses designed to test
improvement and compare results obtained with the OK action to their
counterparts obtained with the clover action. Our preliminary results show a
clear improvement.Comment: 7 pages, 3 figures, Talk presented at 28th International Symposium On
Lattice Field Theory (Lattice 2010) 13-19 Jun 2010, Villasimius, Sardinia,
Ital
High-accuracy critical exponents of O(N) hierarchical sigma models
We perform high-accuracy calculations of the critical exponent gamma and its
subleading exponent for the 3D O(N) Dyson's hierarchical model, for N up to 20.
We calculate the critical temperatures for the nonlinear sigma model measure.
We discuss the possibility of extracting the first coefficients of the 1/N
expansion from our numerical data. We show that the leading and subleading
exponents agreewith Polchinski equation and the equivalent Litim equation, in
the local potential approximation, with at least 4 significant digits.Comment: 4 pages, 2 Figs., uses revte
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Large-scale Quality Control of Cardiac Imaging in Population Studies: Application to UK Biobank
In large population studies such as the UK Biobank (UKBB), quality control of the acquired images by visual assessment is unfeasible. In this paper, we apply a recently developed fully-automated quality control pipeline for cardiac MR (CMR) images to the first 19,265 short-axis (SA) cine stacks from the UKBB. We present the results for the three estimated quality metrics (heart coverage, inter-slice motion and image contrast in the cardiac region) as well as their potential associations with factors including acquisition details and subject-related phenotypes. Up to 14.2% of the analysed SA stacks had sub-optimal coverage (i.e. missing basal and/or apical slices), however most of them were limited to the first year of acquisition. Up to 16% of the stacks were affected by noticeable inter-slice motion (i.e. average inter-slice misalignment greater than 3.4 mm). Inter-slice motion was positively correlated with weight and body surface area. Only 2.1% of the stacks had an average end-diastolic cardiac image contrast below 30% of the dynamic range. These findings will be highly valuable for both the scientists involved in UKBB CMR acquisition and for the ones who use the dataset for research purposes
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