Justin Foley

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A new method for computing all elements of the lattice quark propagator is proposed. The method combines the spectral decomposition of the propagator, computing the lowest eigenmodes exactly, with noisy estimators which are ‘diluted’, i.e. taken to have support only on a subset of time, space, spin or colour. We find that the errors are dramatically reduced(More)
A new method of stochastically estimating the low-lying effects of quark propagation is proposed which allows accurate determinations of temporal correlations of single-hadron and multihadron operators in lattice QCD. The method is well suited for calculations in large volumes. Contributions involving quark propagation connecting hadron sink operators at(More)
A new quark-field smearing algorithm is defined which enables efficient calculations of a broad range of hadron correlation functions. The technique applies a low-rank operator to define smooth fields that are to be used in hadron creation operators. The resulting space of smooth fields is small enough that all elements of the reduced quark propagator can(More)
The semileptonic decay channel B→Dτν is sensitive to the presence of a scalar current, such as that mediated by a charged-Higgs boson. Recently, the BABAR experiment reported the first observation of the exclusive semileptonic decay B→Dτ(-)ν, finding an approximately 2σ disagreement with the standard-model prediction for the ratio R(D)=BR(B→Dτν)/BR(B→Dℓν),(More)
In lattice QCD, the maximum entropy method can be used to reconstruct spectral functions from Euclidean correlators obtained in numerical simulations. We show that at finite temperature the most commonly used algorithm, employing Bryan's method, is inherently unstable at small energies and gives a modification that avoids this. We demonstrate this approach(More)
Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA Department of Physics, University of Maryland, College Park, Maryland 20742, USA Department of Physics, University of the Pacific, Stockton, California 95211, USA Department of Theoretical(More)
Currently, the best way to extract the low-energy predictions of quantum chromodynamics (QCD) is by estimating the QCD path integrals using the Monte Carlo method formulated on a space-time lattice. Determining the hadron mass spectrum is one of the major applications of such an approach. To study a particular state of interest, the energies of all states(More)
We present preliminary results for meson spectral functions at nonzero momentum, obtained from quenched lattice QCD simulations at finite temperature using the Maximal Entropy Method. Twisted boundary conditions are used to have access to many momenta p ∼ T . For light quarks, we observe a drastic modification when heating the system from below to above Tc.(More)