1,569 research outputs found
Administering Health Insurance Mandates
Provides an overview of health insurance mandates and administrative considerations. Based on a review of existing and proposed employer and individual mandates, outlines ways to structure them to be administered fairly and effectively
Taste violations in the scalar correlator in mixed action simulations
We study the behavior of the isovector scalar correlator, which is particularly sensitive to lattice artifacts, using domain-wall valence quarks on a staggered sea (generated by the MILC collaboration). We analyze this according to the prediction from chiral perturbation theory determined by Prelovsek, which indicates that the leading unitarity violations come from taste breaking effects. We show that our data behaves in the way predicted by Prelovsek, thus verifying that the largest contribution to the violations of unitarity which arise at finite lattice spacing can be described by the mixed-action chiral perturbation theory
The neutral kaon mixing parameter B_K from unquenched mixed-action lattice QCD
We calculate the neutral kaon mixing parameter B_K in unquenched lattice QCD
using asqtad-improved staggered sea quarks and domain-wall valence quarks. We
use the "2+1" flavor gauge configurations generated by the MILC Collaboration,
and simulate with multiple valence and sea quark masses at two lattice spacings
of a ~ 0.12 fm and a ~ 0.09 fm. We match the lattice determination of B_K to
the continuum value using the nonperturbative method of Rome-Southampton, and
extrapolate B_K to the continuum and physical quark masses using mixed action
chiral perturbation theory. The "mixed-action" method enables us to control all
sources of systematic uncertainty and therefore to precisely determine B_K; we
find a value of B_K^{MSbar, NDR}(2 GeV) = 0.527(6)(20), where the first error
is statistical and the second is systematic.Comment: 72 pages, 26 figures, 6 tables, uses RevTeX. Discussion about
chiral/continuum extrapolation expanded for clarification, references added,
conclusions remain unchanged, version published in Phys. Rev.
The hadronic vacuum polarization contribution to from full lattice QCD
We determine the contribution to the anomalous magnetic moment of the muon
from the hadronic vacuum polarization diagram using
full lattice QCD and including quarks with physical masses for the first
time. We use gluon field configurations that include , , and
quarks in the sea at multiple values of the lattice spacing, multiple
masses and multiple volumes that allow us to include an analysis of
finite-volume effects. We obtain a result for of
, where the first error is from the lattice calculation and the
second includes systematic errors from missing QED and isospin-breaking effects
and from quark-line disconnected diagrams. Our result implies a discrepancy
between the experimental determination of and the Standard Model of
3.Comment: 14 pages, 10 figures. Discussion of method extended with additional
tests and figures added. Typographical errors correcte
The Kaon B-parameter in Mixed Action Chiral Perturbation Theory
We calculate the kaon B-parameter, B_K, in chiral perturbation theory for a
partially quenched, mixed action theory with Ginsparg-Wilson valence quarks and
staggered sea quarks. We find that the resulting expression is similar to that
in the continuum, and in fact has only two additional unknown parameters. At
one-loop order, taste-symmetry violations in the staggered sea sector only
contribute to flavor-disconnected diagrams by generating an O(a^2) shift to the
masses of taste-singlet sea-sea mesons. Lattice discretization errors also give
rise to an analytic term which shifts the tree-level value of B_K by an amount
of O(a^2). This term, however, is not strictly due to taste-breaking, and is
therefore also present in the expression for B_K for pure G-W lattice fermions.
We also present a numerical study of the mixed B_K expression in order to
demonstrate that both discretization errors and finite volume effects are small
and under control on the MILC improved staggered lattices.Comment: 29 pages, 4 figures; Expanded spurion discussion, other discussions
clarified, version to appear in PR
The coupling with relativistic heavy quarks
We report on a calculation of the coupling in lattice QCD. The
strong matrix element is directly related to the
leading order low-energy constant in heavy meson chiral perturbation theory
(HMPT) for -mesons. We carry out our calculation directly at the
-quark mass using a non-perturbatively tuned clover action that controls
discretisation effects of order and for all . Our
analysis is performed on RBC/UKQCD gauge configurations using domain wall
fermions and the Iwasaki gauge action at two lattice spacings of
GeV, GeV, and unitary pion masses down to 290
MeV. We achieve good statistical precision and control all systematic
uncertainties, giving a final result for the HMPT coupling in the continuum and at the physical light-quark
masses. This is the first calculation performed directly at the physical
-quark mass and lies in the region one would expect from carrying out an
interpolation between previous results at the charm mass and at the static
point.Comment: 7 pages, 2 figures, presented at the 31st International Symposium on
Lattice Field Theory (Lattice 2013), 29 July - 3 August 2013, Mainz, German
B Mixing in the Standard Model and Beyond: Lattice QCD
We give a brief overview and progress report on our lattice QCD calculation
of neutral B mixing hadronic matrix elements needed for Standard Model and
Beyond the Standard Model physics. Reference [1] contains more details and
results.Comment: 3 pages, 0 figures, Proceedings of the 19th Particles and Nuclei
International Conference (PANIC11), Cambridge, MA, U.S.A., July 201
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