Domain Wall Lattice QCD Research Articles

Strong Running Coupling from the Gauge Sector of Domain Wall Lattice QCD with Physical Quark Masses.

We report on the first computation of the strong running coupling at the physical point (physical pion mass) from the ghost-gluon vertex, computed from lattice simulations with three flavors of domain wall fermions. We find α_{MS[over ¯]}(m_{Z}^{2})=0.1172(11), in remarkably good agreement with the world-wide average. Our computational bridge to this value is the Taylor-scheme strong coupling, which has been revealed of great interest by itself because it can be directly related to the quark-gluon interaction kernel in continuum approaches to the QCD bound-state problem.

BSM Kaon Mixing at the Physical Point

We present a progress update on the RBC-UKQCD calculation of beyond the standard model (BSM) kaon mixing matrix elements at the physical point. Simulations are performed using 2+1 flavour domain wall lattice QCD with the Iwasaki gauge action at 3 lattice spacings and with pion masses ranging from 430 MeV to the physical pion mass.

The decay constants fD and {f}_{D_s} in the continuum limit of Nf = 2 + 1 domain wall lattice QCD

We present results for the decay constants of the D and Ds mesons computed in lattice QCD with Nf = 2 + 1 dynamical flavours. The simulations are based on RBC/UKQCD’s domain wall ensembles with both physical and unphysical light-quark masses and lattice spacings in the range 0.11-0.07 fm. We employ the domain wall discretisation for all valence quarks.The results in the continuum limit are fD = 208.7(2.8)stat(− 1.8+ 2.1)sysMeV and {f}_{D_s}=246.4{(1.3)}_{mathrm{stat}}{left({}_{-1.9}^{+1.3}right)}_{mathrm{sys}}mathrm{M}mathrm{e}mathrm{V} and {f}_{D_s}={f}_D=1.667{(77)}_{mathrm{stat}}{left({}_{-43}^{+57}right)}_{mathrm{sys}} . Using these results in a Standard Model analysis we compute the predictions |Vcd| = 0.2185(50)exp(− 37+ 35)lat and |Vcs| = 1.011(16)exp(− 9+ 4)lat for the CKM matrix elements.

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).

27aSM-6 Nucleon isovector form factors and structure functions in 2+1-falvor domain-wall lattice QCD at physical mass

27aSM-6 Nucleon isovector form factors and structure functions in 2+1-falvor domain-wall lattice QCD at physical mass

The kaon semileptonic form factor in N f = 2 + 1 domain wall lattice QCD with physical light quark masses

We present the first calculation of the kaon semileptonic form factor with sea and valence quark masses tuned to their physical values in the continuum limit of 2+1 flavour domain wall lattice QCD. We analyse a comprehensive set of simulations at the phenomenologically convenient point of zero momentum transfer in large physical volumes and for two different values of the lattice spacing. Our prediction for the form factor is f+(0)=0.9685(34)(14) where the first error is statistical and the second error systematic. This result can be combined with experimental measurements of K->pi decays for a determination of the CKM-matrix element for which we predict |Vus|=0.2233(5)(9) where the first error is from experiment and the second error from the lattice computation.

The kaon semileptonic form factor with near physical domain wall quarks

We present a new calculation of the K->pi semileptonic form factor at zero momentum transfer in domain wall lattice QCD with Nf=2+1 dynamical quark flavours. By using partially twisted boundary conditions we simulate directly at the phenomenologically relevant point of zero momentum transfer. We perform a joint analysis for all available ensembles which include three different lattice spacings (a=0.09-0.14fm), large physical volumes (m_pi*L>3.9) and pion masses as low as 171 MeV. The comprehensive set of simulation points allows for a detailed study of systematic effects leading to the prediction f+(0)=0.9670(20)(+18/-46), where the first error is statistical and the second error systematic. The result allows us to extract the CKM-matrix element |Vus|=0.2237(+13/-8) and confirm first-row CKM-unitarity in the Standard Model at the sub per mille level.