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Register a new userHeavy Domain Wall Fermions: The RBC and UKQCD charm physics program
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We review the domain wall charm physics program of the RBC and UKQCD collaborations based on simulations including ensembles with physical pion mass. We summarise our current set-up and present a status update on the decay constants $f_D$, $f_{D_s}$, the charm quark mass, heavy-light and heavy-strange bag parameters and the ratio $xi$.
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We present results showing that Domain Wall fermions are a suitable discretisation for the simulation of heavy quarks. This is done by a continuum scaling study of charm quarks in a Mobius Domain Wall formalism using a quenched set-up. We find that discretisation effects remain well controlled by the choice of Domain Wall parameters preparing the ground work for the ongoing dynamical $2+1f$ charm program of RBC/UKQCD.
We present RBC/UKQCDs charm project using $N_f=2+1$ flavour ensembles with inverse lattice spacings in the range $1.73-2.77,mathrm{GeV}$ and two physical pion mass ensembles. Domain wall fermions are used for the light as well as the charm quarks. We discuss our strategy for the extraction of the decay constants $f_D$ and $f_{D_s}$ and their extrapolation to the continuum limit, physical pion masses and the physical heavy quark mass. Our preliminary results are $f_D=208.7(2.8),mathrm{MeV}$ and $f_{D_s}=246.4(1.9),mathrm{MeV}$ where the quoted error is statistical only. We outline our current approach to extend the reach in the heavy quark mass and present preliminary results.
We present a study of charm physics using RBC/UKQCD 2+1 flavour physical point domain wall fermion ensembles for the light quarks as well as for the valence charm quark. After a brief motivation of domain wall fermions as a suitable heavy quark discretisation we will show first results for masses and matrix elements.
We present RBC heavy-light meson spectroscopy with quenched DBW2 gauge configurations at lattice cutoff of about 3 GeV. Both heavy and light quarks are described by domain-wall fermions (DWF). The heavy quark mass ranges between 0.1 and 0.4 lattice units, covering charm. The light quark mass ranges between 0.008 and 0.04, covering strange. In particular, we discuss charmed (D and D*) and charm-strange (Ds and DsJ) mesons with spin-parity JP= 0+/- and 1+/-. The preliminary results indicate that DWF describe charm on the quenched DBW2 ensemble at this cutoff. The masses of the JP=0+/- and 1+/- D, D*, Ds and DsJ meson states are well reproduced to within a few %; their parity splitting, DeltaJ, are better reproduced than previous works, with only 10-20 % over estimations; the experimental observation that the splitting for non-strange states is bigger than that for strange states is reproduced as well; but the hyperfine splittings are only 60-65 % reproduced. Regarding the depenence on heavy quark mass, J=0 and J=1 parity splittings are degenerate for heavy quark mass heavier than 0.2-0.3 lattice units a; the J=0 parity splitting increases as the heavy quark mass decreases further while the J=1 splitting does not.
We report on an exploratory study of domain wall fermions (DWF) as a lattice regularisation for heavy quarks. Within the framework of quenched QCD with the tree-level improved Symanzik gauge action we identify the DWF parameters which minimise discretisation effects. We find the corresponding effective 4$d$ overlap operator to be exponentially local, independent of the quark mass. We determine a maximum bare heavy quark mass of $am_happrox 0.4$, below which the approximate chiral symmetry and O(a)-improvement of DWF are sustained. This threshold appears to be largely independent of the lattice spacing. Based on these findings, we carried out a detailed scaling study for the heavy-strange meson dispersion relation and decay constant on four ensembles with lattice spacings in the range $2.0-5.7,mathrm{GeV}$. We observe very mild $a^2$ scaling towards the continuum limit. Our findings establish a sound basis for heavy DWF in dynamical simulations of lattice QCD with relevance to Standard Model phenomenology.
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