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RBC

Publications and source records attributed to RBC.

5 recordsLinked to original sources
arXiv2014

Domain wall QCD with physical quark masses

We present results for several light hadronic quantities ($f_\pi$, $f_K$, $B_K$, $m_{ud}$, $m_s$, $t_0^{1/2}$, $w_0$) obtained from simulations of 2+1 flavor domain wall lattice QCD with large physical volumes and nearly-physical pion masses at two lattice spacings. We perform a short, O(3)%, extrapolation in pion mass to the physical values by combining our new data in a simultaneous chiral/continuum `global fit' with a number of other ensembles with heavier pion masses. We use the physical values of $m_\pi$, $m_K$ and $m_\Omega$ to determine the two quark masses and the scale - all other quantities are outputs from our simulations. We obtain results with sub-percent statistical errors and negligible chiral and finite-volume systematics for these light hadronic quantities, including: $f_\pi$ = 130.2(9) MeV; $f_K$ = 155.5(8) MeV; the average up/down quark mass and strange quark mass in the $\bar {\rm MS}$ scheme at 3 GeV, 2.997(49) and 81.64(1.17) MeV respectively; and the neutral kaon mixing parameter, $B_K$, in the RGI scheme, 0.750(15) and the $\bar{\rm MS}$ scheme at 3 GeV, 0.530(11).

hep-lat↗
arXiv2010

Preliminary results of $ΔI=1/2$ and $3/2$, $K$ to $ππ$ Decay Amplitudes from Lattice QCD

We report a direct lattice calculation of the $K$ to $ππ$ decay matrix elements for both $ΔI=1/2$ and $3/2$ channels on 2+1 flavor, domain wall fermion, $16^3\times32$ lattices with zero $ππ$ relative momentum and $m_π=420$ MeV. All $K^0$ to $ππ$ contractions are carefully listed and calculated. The decay into the isospin zero $ππ$ final state, which receives contributions from the disconnected graphs, is very difficult to calculate, but a clear signal in the similar disconnected $ππ$ correlator can be seen. Preliminary results, some with large errors, will be presented for the various contributions to the renormalized weak matrix elements $A_0$ and $A_2$. We obtain Re$(A_0)$ with $25%$ error in the case of zero momentum on shell decay, and find a factor of 6 enhancement for the $ΔI=1/2$ rule in the $420$ MeV pion system.

hep-lat↗
arXiv2007

2+1 flavour Domain Wall Fermion simulations by the RBC and UKQCD collaborations

We review simulations of dynamical domain wall fermions at a fixed inverse lattice spacing of 1.73GeV and with pion masses as light as 330MeV and spatial dimensions as large as 2.7fm performed by the RBC and UKQCD collaborations. These results include pseudoscalar masses and decay constants and low energy constants of the chiral effective lagrangian. We also review results for the neutral kaon mixing amplitude $B_K$, the Kl3 form factor, pseudoscalar meson structure, and vector meson decay constants. In the baryon sector we review results for the spectrum, and nucleon form factors and structure functions. Highlights of our programme include preliminary quark masses, and determinations of $V_{us}$ from both $f_K/f_π$ and from Kl3, and an updated result for $B_K$. We find significant finite volume effects in the nucleon axial charge $g_A$ for our $m_π=330$ MeV ensemble on a $(2.7 {\rm fm})^3$ lattice, and highlight the importance of large physical volumes for non-trivial nucleon physics.

hep-lat↗
arXiv2005

Baryons in 2+1 flavour domain wall QCD

We present results for some of the light baryon masses and their excited states in 2+1 flavour domain wall QCD. We considered several lattice spacings, with the DBW2 and Iwasaki gauge actions and different sea quark masses on a volume of $16^3\times32$ and a fifth dimension of size 8. All data were generated on the QCDOC machines. Despite large residual massses and a limited number of sea quark mass values with which to perform chiral extrapolations, our results are in reasonable agreement with experiment and scale within errors. Finite size effects on most ensembles appear to be small.

hep-lat↗