3,396 research outputs found
Tuning Fermilab Heavy Quarks in 2+1 Flavor Lattice QCD with Application to Hyperfine Splittings
We report the non-perturbative tuning of parameters--- kappa_c, kappa_b, and
kappa_crit ---that determine the heavy-quark mass in the Fermilab action. This
requires the computation of the masses of Ds^(*) and Bs^(*) mesons comprised of
a Fermilab heavy quark and a staggered light quark. Additionally, we report the
hyperfine splittings for Ds and Bs mesons as a cross-check of our simulation
and analysis methods. We find a splitting of 145 +/- 15 MeV for the Ds system
and 40 +/- 9 MeV for the Bs system. These are in good agreement with the
Particle Data Group average values of 143.9 +/- 0.4 MeV and 46.1 +/- 1.5 MeV,
respectively. The calculations are carried out with the MILC 2+1 flavor gauge
configurations at three lattice spacings approximately 0.15, 0.12, and 0.09
fm.Comment: 34 pages, 8 figures, 26 tables; some sections rearranged for clarity;
conclusions unchanged; version accepted by Phys. Rev.
A response to “Likelihood ratio as weight of evidence: a closer look” by Lund and Iyer
Recently, Lund and Iyer (L&I) raised an argument regarding the use of likelihood ratios in court. In our view, their argument is based on a lack of understanding of the paradigm. L&I argue that the decision maker should not accept the expert’s likelihood ratio without further consideration. This is agreed by all parties. In normal practice, there is often considerable and proper exploration in court of the basis for any probabilistic statement. We conclude that L&I argue against a practice that does not exist and which no one advocates. Further we conclude that the most informative summary of evidential weight is the likelihood ratio. We state that this is the summary that should be presented to a court in every scientific assessment of evidential weight with supporting information about how it was constructed and on what it was based
Visualization of semileptonic form factors from lattice QCD
Comparisons of lattice-QCD calculations of semileptonic form factors with
experimental measurements often display two sets of points, one each for
lattice QCD and experiment. Here we propose to display the output of a
lattice-QCD analysis as a curve and error band. This is justified, because
lattice-QCD results rely in part on fitting, both for the chiral extrapolation
and to extend lattice-QCD data over the full physically allowed kinematic
domain. To display an error band, correlations in the fit parameters must be
taken into account. For the statistical error, the correlation comes from the
fit. To illustrate how to address correlations in the systematic errors, we use
the Becirevic-Kaidalov parametrization of the D -> pi l nu and D -> K l nu form
factors, and a analyticity-based fit for the B -> pi l nu form factor f_+.Comment: 6 pp; v2 conforms with published version (one additional sentence and
reference to clarify a point
Short-distance matrix elements for D0-meson mixing from Nf=2+1 lattice QCD
We calculate in three-flavor lattice QCD the short-distance hadronic matrix elements of all five ΔC=2 four-fermion operators that contribute to neutral
D-meson mixing both in and beyond the Standard Model. We use the MILC Collaboration’s Nf=2+1 lattice gauge-field configurations generated with asqtad-improved staggered sea quarks. We also employ the asqtad action for the valence light quarks and use the clover action with the Fermilab interpretation for the charm quark. We analyze a large set of ensembles with pions as light as lattice gauge-field configurations generated with asqtad-improved staggered sea quarks. We also employ the asqtad action for the valence light quarks and use the clover action with the Fermilab interpretation for the charm quark. We analyze a large set of ensembles with pions as light as Mπ ≈ 180 MeV and lattice spacings as fine as a ≈ 0.045 fm, thereby enabling good control over the extrapolation to the physical pion mass and continuum limit. We obtain for the matrix elements in the MS−NDR scheme using the choice of evanescent operators proposed by Beneke et al., evaluated at 3 GeV, ⟨D0|Oi|¯D0⟩ = {0.0805(55)16),−0.1561(70)(31), 0.0464(31)(9), 0.2747(129)(55), 0.1035(71)(21)} GeV4 (i=1–5). The errors shown are from statistics and lattice systematics, and the omission of charmed sea quarks, respectively. To illustrate the utility of our matrix-element results, we place bounds on the scale of CP-violating new physics in D0 mixing, finding lower limits of about 10–50×103 TeV for couplings of O(1). To enable our results to be employed in more sophisticated or model-specific phenomenological studies, we provide the correlations among our matrix-element results. For convenience, we also present numerical results in the other commonly used scheme of Buras, Misiak, and Urban
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