An accurate calculation of the nucleon axial charge with lattice QCD

We report on a lattice QCD calculation of the nucleon axial charge, $g_A$, using M\"{o}bius Domain-Wall fermions solved on the dynamical $N_f=2+1+1$ HISQ ensembles after they are smeared using the gradient-flow algorithm. The calculation is performed with three pion masses, $m_\pi\sim\{310,220,130\}$ MeV. Three lattice spacings ($a\sim\{0.15,0.12,0.09\}$ fm) are used with the heaviest pion mass, while the coarsest two spacings are used on the middle pion mass and only the coarsest spacing is used with the near physical pion mass. On the $m_\pi\sim220$ MeV, $a\sim0.12$ fm point, a dedicated volume study is performed with $m_\pi L \sim \{3.22,4.29,5.36\}$. Using a new strategy motivated by the Feynman-Hellmann Theorem, we achieve a precise determination of $g_A$ with relatively low statistics, and demonstrable control over the excited state, continuum, infinite volume and chiral extrapolation systematic uncertainties, the latter of which remains the dominant uncertainty. Our final determination at 2.6\% total uncertainty is $g_A = 1.278(21)(26)$, with the first uncertainty including statistical and systematic uncertainties from fitting and the second including model selection systematics related to the chiral and continuum extrapolation. The largest reduction of the second uncertainty will come from a greater number of pion mass points as well as more precise lattice QCD results near the physical pion mass.Comment: 17 pages + 11 pages of references and appendices. 15 figures. Interested readers can download the Python analysis scripts and an hdf5 data file at https://github.com/callat-qcd/project_gA_v

Doing our work better, together: a relationship-based approach to defining the quality improvement agenda in trauma care

Article presents a study conducted at Gold Coast University Hospital that aimed to define and improve relational aspects of trauma care and facilitate co-creation of targeted interventions designed to improve team relationships and performance

Scale setting the M\"obius Domain Wall Fermion on gradient-flowed HISQ action using the omega baryon mass and the gradient-flow scales t0t_0 and w0w_0

We report on a sub-percent scale determination using the omega baryon mass and gradient-flow methods. The calculations are performed on 22 ensembles of $N_f=2+1+1$ highly improved, rooted staggered sea-quark configurations generated by the MILC and CalLat Collaborations. The valence quark action used is M\"obius Domain-Wall fermions solved on these configurations after a gradient-flow smearing is applied with a flowtime of $t_{\rm gf}=1$ in lattice units. The ensembles span four lattice spacings in the range $0.06 \lesssim a \lesssim 0.15$ fm, six pion masses in the range $130 \lesssim m_\pi \lesssim 400$ MeV and multiple lattice volumes. On each ensemble, the gradient-flow scales $t_0/a^2$ and $w_0/a$ and the omega baryon mass $a m_\Omega$ are computed. The dimensionless product of these quantities is then extrapolated to the continuum and infinite volume limits and interpolated to the physical light, strange and charm quark mass point in the isospin limit, resulting in the determination of $\sqrt{t_0}=0.1422(14)$ fm and $w_0 = 0.1709(11)$ fm with all sources of statistical and systematic uncertainty accounted for. The dominant uncertainty in this result is the stochastic uncertainty, providing a clear path for a few-per-mille uncertainty, as recently obtained by the Budapest-Marseille-Wuppertal Collaboration.Comment: v3: Published version; v2: Added determination of t_0 as well as w_0; v1: 13 pages plus appendices. The correlation function data, mass results and analysis code accompanying this publication can be found at this github repository: https://github.com/callat-qcd/project_scale_setting_mdwf_his

Detailed analysis of excited state systematics in a lattice QCD calculation of gAg_A

Excited state contamination remains one of the most challenging sources of systematic uncertainty to control in lattice QCD calculations of nucleon matrix elements and form factors. Most lattice QCD collaborations advocate for the use of high-statistics calculations at large time separations ($t_{\rm sep}\gtrsim1$ fm) to combat the signal-to-noise degradation. In this work we demonstrate that, for the nucleon axial charge, $g_A$, the alternative strategy of utilizing a large number of relatively low-statistics calculations at short to medium time separations ($0.2\lesssim t_{\rm sep}\lesssim1$ fm), combined with a multi-state analysis, provides a more robust and economical method of quantifying and controlling the excited state systematic uncertainty, including correlated late-time fluctuations that may bias the ground state. We show that two classes of excited states largely cancel in the ratio of the three-point to two-point functions, leaving the third class, the transition matrix elements, as the dominant source of contamination. On an $m_\pi\approx310$ MeV ensemble, we observe the expected exponential suppression of excited state contamination in the Feynman-Hellmann correlation function relative to the standard three-point function; the excited states of the regular three-point function reduce to the 1% level for $t_{\rm sep} >2$ fm while, for the Feynman-Hellmann correlation function, they are suppressed to 1% at $t_{\rm sep}\approx1$ fm. Independent analyses of the three-point and Feynman-Hellmann correlators yield consistent results for the ground state. However, a combined analysis allows for a more detailed and robust understanding of the excited state contamination, improving the demonstration that the ground state parameters are stable against variations in the excited state model, the number of excited states, and the truncation of early-time or late-time numerical data.Comment: v1: 13 pages plus appendices. The correlation function data and analysis code accompanying this publication can be accessed at this github repository: https://github.com/callat-qcd/project_fh_vs_3p

Photoionization and photoabsorption cross sections for ionospheric calculations

Photoionization and photoabsorption cross sections for N2, O2 and O are presented in a form useful for calculation of solar EUV absorption and photoelectron production. The cross sections are based mostly on the data presented in the reviews by (1969) and (1969).Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/34031/1/0000308.pd

Pennsylvania Folklife Vol. 39, No. 4

• Our Church • Pig Roast • Wooden Jointed Dolls • Coal Jewelry • The Pennsylvania Long Rifle • The Mennonites • Festival Focus • Festival Programs • Blockprinting • Dried Flowers, Wreaths and Baskets • Broom Making • Wood-Turning • Moravian and German Stars • A Plain Costume Primer • Farewell to the Folk Festival Magazinehttps://digitalcommons.ursinus.edu/pafolklifemag/1128/thumbnail.jp

Influence of water pressure dynamics and fluid flow on the streaming-potential response for unsaturated conditions

International audienceA B S T R A C T Streaming-potentials are produced by electrokinetic effects in relation to fluid flow and are used for geophysical prospecting. The aim of this study is to model streaming potential measurements for unsaturated conditions using an empirical approach. A conceptual model is applied to streaming potential measurements obtained from two drainage experiments in sand. The streaming potential data presented here show a non-monotonous behaviour with increasing water saturation, following a pattern that cannot be predicted by existing models. A model involving quasi-static and dynamic components is proposed to reproduce the streaming potential measurements. The dynamic component is based on the first time derivative of the driving pore pressure. The influence of this component is investigated with respect to fluid velocity, which is very different between the two experiments. The results demonstrate that the dynamic component is predominant at the onset of drainage in experiments with the slowest water flow. On the other hand, its influence appears to vanish with increasing drainage velocity. Our results suggest that fluid flow and water distribution at the pore scale have an important influence on the streaming potential response for unsat-urated conditions. We propose to explain this specific streaming potential response in terms of the behaviour of both rock/water interface and water/air interfaces created during desaturation processes. The water/air interfaces are negatively charged, as also observed in the case of water/rock interfaces. Both the surface area and the flow velocity across these interfaces are thought to contribute to the non-monotonous behaviour of the streaming potential coefficient as well as the variations in its amplitude. The non-monotonous behaviour of air/water interfaces created during the flow was highlighted as it was measured and modelled by studies published in the literature. The streaming potential coefficient can increase to about 10 to 40 when water saturation decreases. Such an increase is possible if the amount of water/air interfaces is increased in sufficient amount, which can be the case