Finite volume renormalization scheme for fermionic operators

We propose a new finite volume renormalization scheme. Our scheme is based on the Gradient Flow applied to both fermion and gauge fields and, much like the Schr\"odinger functional method, allows for a nonperturbative determination of the scale dependence of operators using a step-scaling approach. We give some preliminary results for the pseudo-scalar density in the quenched approximation.Comment: Proceedings of the 31st International Symposium on Lattice Field Theory, July 29 - August 3, 2013, Mainz, Germany; LaTeX source, 7 pages, 5 figure

Finite continuum quasi distributions from lattice QCD

We present a new approach to extracting continuum quasi distributions from lattice QCD. Quasi distributions are defined by matrix elements of a Wilson-line operator extended in a spatial direction, evaluated between nucleon states at finite momentum. We propose smearing this extended operator with the gradient flow to render the corresponding matrix elements finite in the continuum limit. This procedure provides a nonperturbative method to remove the power-divergence associated with the Wilson line and the resulting matrix elements can be directly matched to light-front distributions via perturbation theory.Comment: Eight pages, two figures. Proceedings of the 35th International Symposium on Lattice Field Theor

The application of automated perturbation theory to lattice QCD

Predictions of heavy quark parameters are an integral component of precision tests of the Standard Model of particle physics. Experimental measurements of electroweak processes involving heavy hadrons provide stringent tests of Cabibbo-Kobayashi-Maskawa (CKM) matrix unitarity and serve as a probe of new physics. Hadronic matrix elements parameterise the strong dynamics of these interactions and these matrix elements must be calculated nonperturbatively. Lattice quantum chromodynamics (QCD) provides the framework for nonperturbative calculations of QCD processes. Current lattices are too coarse to directly simulate b quarks. Therefore an effective theory, nonrelativistic QCD (NRQCD), is used to discretise the heavy quarks. High precision simulations are required so systematic uncertainties are removed by improving the NRQCD action. Precise simulations also require improved sea quark actions, such as the highly-improved staggered quark (HISQ) action. The renormalisation parameters of these actions cannot be feasibly determined by hand and thus automated procedures have been developed. In this dissertation I apply automated lattice pertubartion theory to a number of heavy quark calculations. I first review the fundamentals of lattice QCD and the construction of lattice NRQCD. I then motivate and discuss lattice perturbation theory in detail, focussing on the tools and techniques that I use in this dissertation. I calculate the two-loop tadpole improvement factors for improved gluons with improved light quarks. I then compute the renormalisation parameters of NRQCD. I use a mix of analytic and numerical methods to extract the one-loop radiative corrections to the higher order kinetic operators in the NRQCD action. I then employ a fully automated procedure to calculate the heavy quark energy shift at two-loops. I use this result to extract a new prediction of the mass of the b quark from lattice NRQCD simulations by the HPQCD collaboration. I also review the calculation of the radiative corrections to the chromo-magnetic operator in the NRQCD action. This computation is the first outcome of our implementation of background field gauge for automated lattice perturbation theory. Finally, I calculate the heavy-light currents for highly-improved NRQCD heavy quarks with massless HISQ light quarks and discuss the application of these results to nonperturbative studies by the HPQCD collaboration

A Prospective Evaluation of PTSD Symptoms following CPAP Treatment for Sleep-disordered Breathing in Veterans

Previous research has observed elevated rates of OSA observed in individuals with PTSD compared to the general population. Retrospective studies suggest that successful treatment of OSA in individuals with PTSD is related to reductions in nightmares and overall PTSD symptom severity. The purpose of the current study was to extend this research by prospectively examining PTSD sympomatology in a sample of Veterans initiating treatment for OSA. Participants were 47 Veterans presenting to a VAMC Neurology Sleep Clinic for overnight polysomnography. Veterans were eligible if they were: (a) diagnosed with OSA; (b) received continuous positive airway pressure (CPAP) treatment; and (c) had a minimum score of 25 on the baseline administration of the PCL. The majority of the sample were male (n = 42; 89.4%) and Caucasian (n = 23; 48.9%) or African American (n = 22; 46.8%), with a mean age of 53.5 years. Veterans completed self-report questionnaires across two pre-treatment and two post-treatment (two weeks and four weeks from treatment initiation) time points. A 2 (treatment compliance status) x 4 (time) mixed model repeated measures analysis was conducted on PTSD symptom severity as measured by the PCL administered at each time point. A statistically significant compliance status x time interaction emerged, (F(3, 102.15) = 5.66. p = .001) such that CPAP-compliant Veterans reported a statistically significant reduction in PTSD symptoms from pre to post-treatment, whereas CPAP non-compliant Veterans did not. These findings suggest that successful treatment of a physical sleep disorder like OSA is associated with a subsequent reduction of posttraumatic distress