876 research outputs found
RI/MOM and RI/SMOM renormalization of overlap quark bilinears on domain wall fermion configurations
Renormalization constants (RCs) of overlap quark bilinear operators on
2+1-flavor domain wall fermion configurations are calculated by using the
RI/MOM and RI/SMOM schemes. The scale independent RC for the axial vector
current is computed by using a Ward identity. Then the RCs for the quark field
and the vector, tensor, scalar and pseudoscalar operators are calculated in
both the RI/MOM and RI/SMOM schemes. The RCs are converted to the
scheme and we compare the numerical results from using the
two intermediate schemes. The lattice size is and the inverse
spacing .Comment: Minor changes and updates of Figure 10 and 15 to be more clea
Meson Mass Decomposition
Hadron masses can be decomposed as a sum of components which are defined
through hadronic matrix elements of QCD operators. The components consist of
the quark mass term, the quark energy term, the glue energy term and the trace
anomaly term. We calculate these components of mesons with lattice QCD for the
first time. The calculation is carried out with overlap fermion on flavor
domain-wall fermion gauge configurations. We confirm that of the
light pion mass comes from the quark mass and comes from the quark
energy, whereas, the contributions are found to be the other way around for the
mass. The combined glue components contribute for both
mesons. It is interesting to observe that the quark mass contribution to the
mass of the vector meson is almost linear in quark mass over a large quark mass
region below the charm quark mass. For heavy mesons, the quark mass term
dominates the masses, while the contribution from the glue components is about
MeV for the heavy pseudoscalar and vector mesons. The charmonium
hyperfine splitting is found to be dominated by the quark energy term which is
consistent with the quark potential model.Comment: 7 Pages, 4 figures, contribution to the 32nd International Symposium
on Lattice Field Theory (Lattice 2014), 23-28 June 2014, Columbia University,
New York, NY, US
N and strangeness sigma terms at the physical point with chiral fermions
Lattice QCD calculations with chiral fermions of the N sigma term
and strangeness sigma term including chiral
interpolation with continuum and volume corrections are provided in this work,
with the excited-state contaminations subtracted properly. We calculate the
scalar matrix element for the light/strange quark directly and find
MeV, with the disconnected insertion part
contributing 20(12)(4)\%, and MeV, which is
somewhat smaller than . The ratio of the strange/light scalar
matrix elements is = 0.09(3)(1).Comment: 7 pages, 5 figures, expanded version accepted for publication in PR
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
Stochastic method with low mode substitution for nucleon isovector matrix elements
We introduce a stochastic sandwich method with low-mode substitution to
evaluate the connected three-point functions. The isovector matrix elements of
the nucleon for the axial-vector coupling , scalar couplings and
the quark momentum fraction are calculated with
overlap fermion on 2+1 flavor domain-wall configurations on a
lattice at MeV with lattice spacing fm.Comment: 15 pages, 13 figures, the version accepted by PR
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
Sea Quarks Contribution to the Nucleon Magnetic Moment and Charge Radius at the Physical Point
We report a comprehensive analysis of the light and strange disconnected-sea
quarks contribution to the nucleon magnetic moment, charge radius, and the
electric and magnetic form factors. The lattice QCD calculation includes
ensembles across several lattice volumes and lattice spacings with one of the
ensembles at the physical pion mass. We adopt a model-independent extrapolation
of the nucleon magnetic moment and the charge radius. We have performed a
simultaneous chiral, infinite volume, and continuum extrapolation in a global
fit to calculate results in the continuum limit. We find that the combined
light and strange disconnected-sea quarks contribution to the nucleon magnetic
moment is and to the nucleon mean
square charge radius is
fm which is about of the difference between the of electron-proton scattering and that of muonic atom and so
cannot be ignored in obtaining the proton charge radius in the lattice QCD
calculation. The most important outcome of this lattice QCD calculation is that
while the combined light-sea and strange quarks contribution to the nucleon
magnetic moment is small at about , a negative contribution to
the proton mean square charge radius and a relatively larger positive
contribution to the neutron mean square charge radius come from
the sea quarks in the nucleon. For the first time, by performing global fits,
we also give predictions of the light and strange disconnected-sea quarks
contributions to the nucleon electric and magnetic form factors at the physical
point and in the continuum and infinite volume limits in the momentum transfer
range of GeV.Comment: Published Version, 26 pages, 8 figure
Strange and Charm Quark Spins from Anomalous Ward Identity
We present a calculation of the strange and charm quark contributions to the
nucleon spin from the anomalous Ward identity (AWI). It is performed with
overlap valence quarks on 2+1-flavor domain-wall fermion gauge configurations
on a lattice with the light sea mass at MeV.
To satisfy the AWI, the overlap fermion for the pseudoscalar density and the
overlap Dirac operator for the topological density, which do not have
multiplicative renormalization, are used to normalize the form factor of the
local axial-vector current at finite . For the charm quark, we find that
the negative pseudoscalar term almost cancels the positive topological term.
For the strange quark, the pseudoscalar term is less negative than that of the
charm. By imposing the AWI, the strange at is obtained by a
global fit of the pseudoscalar and the topological form factors, together with
and the induced pseudoscalar form factor at finite .
The chiral extrapolation to the physical pion mass gives .Comment: 8 pages, 9 figures. Updated version where a sign error is correcte
- …