236 research outputs found
Hadron-Hadron Interactions from Lattice QCD: isospin-1 scattering length
We present results for the interaction of two kaons at maximal isospin. The
calculation is based on flavour gauge configurations generated by
the European Twisted Mass Collaboration with pion masses ranging from about
to at three values of the lattice spacing. The
elastic scattering length is calculated at several values of the
bare strange and light quark masses. We find as
the result of a combined extrapolation to the continuum and to the physical
point, where the first error is statistical, and the three following are
systematical. This translates to .Comment: 28 pages, 18 tables, 14 figure
Cooperation between Authorities and Industry, Illustrated by a Case Study on C.I. Disperse Blue 79:1
Hadron-Hadron Interactions from Lattice QCD: isospin-2 scattering length
We present results for the scattering length using
twisted mass lattice QCD for three values of the lattice spacing and a range of
pion mass values. Due to the use of Laplacian Heaviside smearing our
statistical errors are reduced compared to previous lattice studies. A detailed
investigation of systematic effects such as discretisation effects, volume
effects, and pollution of excited and thermal states is performed. After
extrapolation to the physical point using chiral perturbation theory at NLO we
obtain .Comment: Edited for typos, overhauled figures, more detailed comparison to
existing lattice result
Isospin-0 s-wave scattering length from twisted mass lattice QCD
We present results for the isospin-0 s-wave scattering length
calculated with Osterwalder-Seiler valence quarks on Wilson twisted mass gauge
configurations. We use three ensembles with unitary (valence) pion
mass at its physical value (250MeV), at 240MeV (320MeV) and
at 330MeV (400MeV), respectively. By using the stochastic Laplacian
Heaviside quark smearing method, all quark propagation diagrams contributing to
the isospin-0 correlation function are computed with sufficient
precision. The chiral extrapolation is performed to obtain the scattering
length at the physical pion mass. Our result agrees reasonably well with various experimental measurements and
theoretical predictions. Since we only use one lattice spacing, certain
systematics uncertainties, especially those arising from unitary breaking, are
not controlled in our result.Comment: 21 pages, 5 figures, 6 table
A Systematic Search for Structure-Activity Relationships of Skin Contact Sensitizers: Methodology
A computerized resource for the systematic evaluation of the structure-activity relationships and other aspects of contact allergens is described. This resource consists of a data base of results of contact dermatitis tests and a structural classification scheme for contact allergens that is called a Structure-Activity (S/A) Tree. The data base now contains approximately 2200 test results extracted from the journal Contact Dermatitis (1975–1982) and is continually being expanded. The S/A Tree is being developed to provide an index to structure-activity relationships of contact allergens; 63 structural groups are currently indexed. Analyses of benzoquinones and gallic acid esters are presented as examples of the potential application of this resource to such problems as the identification of potential cross-reactants, appropriate test concentrations and vehicles, and the reliability of available test results
First Physics Results at the Physical Pion Mass from Wilson Twisted Mass Fermions at Maximal Twist
We present physics results from simulations of QCD using dynamical
Wilson twisted mass fermions at the physical value of the pion mass. These
simulations were enabled by the addition of the clover term to the twisted mass
quark action. We show evidence that compared to previous simulations without
this term, the pion mass splitting due to isospin breaking is almost completely
eliminated. Using this new action, we compute the masses and decay constants of
pseudoscalar mesons involving the dynamical up and down as well as valence
strange and charm quarks at one value of the lattice spacing,
fm. Further, we determine renormalized quark masses as well as their
scale-independent ratios, in excellent agreement with other lattice
determinations in the continuum limit. In the baryon sector, we show that the
nucleon mass is compatible with its physical value and that the masses of the
baryons do not show any sign of isospin breaking. Finally, we compute
the electron, muon and tau lepton anomalous magnetic moments and show the
results to be consistent with extrapolations of older ETMC data to the
continuum and physical pion mass limits. We mostly find remarkably good
agreement with phenomenology, even though we cannot take the continuum and
thermodynamic limits.Comment: 45 pages, 15 figure
The Euler-Maruyama approximation for the absorption time of the CEV diffusion
A standard convergence analysis of the simulation schemes for the hitting
times of diffusions typically requires non-degeneracy of their coefficients on
the boundary, which excludes the possibility of absorption. In this paper we
consider the CEV diffusion from the mathematical finance and show how a weakly
consistent approximation for the absorption time can be constructed, using the
Euler-Maruyama scheme
Isospin-0 ππ scattering from twisted mass lattice QCD
We present results for the isospin-0 s-wave scattering length
calculated in twisted mass lattice QCD. We use three ensembles with
unitary pion mass at its physical value, 240~MeV and 330~MeV respectively. We
also use a large set of ensembles with unitary pion masses
varying in the range of 230~MeV - 510~MeV at three different values of the
lattice spacing. A mixed action approach with the Osterwalder-Seiler action in
the valence sector is adopted to circumvent the complications arising from
isospin symmetry breaking of the twisted mass quark action. Due to the
relatively large lattice artefacts in the ensembles, we do not
present the scattering lengths for these ensembles. Instead, taking the
advantage of the many different pion masses of these ensembles, we
qualitatively discuss the pion mass dependence of the scattering properties of
this channel based on the results from the ensembles. The
scattering length is computed for the ensembles and the chiral
extrapolation is performed. At the physical pion mass, our result agrees reasonably well with various
experimental measurements and theoretical predictions
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