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Register a new userContinuum results for light hadrons from 2+1 flavor DWF ensembles
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From simultaneous fits to the data from the 2+1 flavor DWF ensembles generated by the RBC and UKQCD collaborations at two different lattice spacings, we present preliminary continuum results for light hadrons. We focus on light pseudoscalar decay constants and quark masses. Several approaches to the calculation of the lattice spacing are discussed and the errors associated with the chiral extrapolation are explained. We make use of reweighting in the dynamical strange quark mass such that our ensembles have a self-consistently determined strange quark mass.
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Nucleon isovector vector- and axialvector-current form factors, the renormalized isovector transversity and scalar charge, and the bare quark momentum and helicity moments of isovector structure functions are reported with improved statistics from two recent RBC+UKQCD 2+1-flavor dynamical domain-wall fermions ensembles: Iwasaki(times)DSDR gauge (32^3times64) at inverse lattice spacing of 1.38 GeV and pion mass of 249 and 172 MeV.
We report the status of nucleon structure calculations on the (2+1)-flavor dynamical domain-wall fermions ensembles with pion masses as low as 180 and 250 MeV on a lattice with about 4.6 fm spatial extent. A combination of the Iwasaki+dislocation- suppressing-determinant-ratio (I+DSDR) gauge action and DWF fermion action allows us to generate these ensembles at cutoff of about 1.4 GeV while keeping the residual mass small. Nucleon source Gaussian smearing has been optimized. Preliminary nucleon mass estimates are 0.98 and 1.05 GeV.
We report the current status of the on-going lattice-QCD calculations of nucleon isovector axial charge, g_A, using the RBC/UKQCD 2+1-flavor dynamical domain-wall fermion ensembles at lattice cutoff of about a^{-1}=1.4 GeV in a spatial volume (L = 4.6 fm)^3. The result from the ensemble with m_pi = 250 MeV pion mass, corresponding to the finite-size scaling parameter m_pi L sim 5.8, agrees well with an earlier result at a^{-1}=1.7 GeV, L = 2.8 fm, and m_pi = 420 MeV, with similar m_pi L. This suggests the systematic error from excited-state contamination is small in both ensembles and about 10-% deficit in g_A we are observing is likely a finite-size effect that scales with m_pi L. We also report the result from the lighter, m_pi = 170 MeV ensemble.
The current status of some nucleon isovector observables, the vector charge, (g_V), axial charge, (g_A), quark momentum fraction, (langle x rangle_{u-d}), and quark helicity fraction, (langle x rangle_{Delta u - Delta d}), calculated using recent RBC/UKQCD 2+1-flavor dynamical domain-wall fermions (DWF) lattice QCD ensembles are reported: with Iwasaki gauge action at inverse lattice spacing, (a^{-1}), of about 1.7 GeV, linear lattice extent, (L), of about 2.7 fm, pion mass, (m_pi), of about 420 and 330 MeV, and with Iwasaki(times)DSDR gauge action at (a^{-1}) of about 1.4 GeV, (L) of about 4.6 fm, and (m_pi) of about 250 and 170 MeV. The calculations have been refined with enhanced statistics, in particular through successful application of the all-mode-averaging (AMA) technique for the 170- and 330-MeV ensembles. As a result, the precision agreement seen in the charge ratio, (g_A/g_V), for 420-MeV and 250-MeV ensembles that share the finite-size scaling parameter (m_pi L) of about 5.8 is more significant with new values of 1.17(2) and 1.18(4) respectively. We also studied the dependence on the source-sink separation in the lightest ensemble of 170-MeV, by comparing the cases with the separation of about 1.0 and 1.3 fm and did not see any dependence: contamination from the excited states are well under control in our choice of source and sink smearing. The axial charge, (g_A) and the ratio, (g_A/g_V), shows a long-range autocorrelation that extends the entire range of configurations that were so far analyzed, almost 700 hybrid Molecular Dynamics time, in the lightest ensemble of (m_pi=170) MeV. The other observables do not show any autocorrelation with the interval of 16 trajectories.
Results of hadron spectroscopy with two dynamical mass-degenerate chirally improved quarks are presented. Three ensembles with pion masses of 322(5), 470(4) and 525(7) MeV, lattices of size 16^3 times 32, and lattice spacings close to 0.15 fm are investigated. We discuss the possible appearance of scattering states, considering masses and eigenvectors. Partially quenched results in the scalar channel suggest the presence of a 2-particle state, however, in most channels we cannot identify them. Where available, we compare to results from quenched simulations using the same action.
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