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تسجيل مستخدم جديدFinite-size scaling in nucleon axial charge from 2+1-flavor DWF lattice QCD
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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.
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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.
We present results for the nucleon axial charge g_A at a fixed lattice spacing of 1/a=1.73(3) GeV using 2+1 flavors of domain wall fermions on size 16^3x32 and 24^3x64lattices (L=1.8 and 2.7 fm) with length 16 in the fifth dimension. The length of th
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The nucleon axial charge is calculated as a function of the pion mass in full QCD. Using domain wall valence quarks and improved staggered sea quarks, we present the first calculation with pion masses as light as 354 MeV and volumes as large as (3.5
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