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Register a new userDomain Wall Charm Physics with Physical Pion Masses: Decay constants, bag and $xi$ parameters
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We provide an overview of RBC/UKQCDs charm project on 2+1 flavour physical pion mass ensembles using Mobius Domain Wall Fermions for the light as well as for the charm quark. We discuss the analysis strategy in detail and present results at the different stages of the analysis for $D$ and $D_s$ decay constants as well as the bag and $xi$ parameters. We also discuss future approaches to extend the reach in the heavy quark mass.
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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 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 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).
We estimate the effects on the decay constants of charmonium and on heavy meson masses due to the charm quark in the sea. Our goal is to understand whether for these quantities $N_f=2+1$ lattice QCD simulations provide results that can be compared with experiments or whether $N_f=2+1+1$ QCD including the charm quark in the sea needs to be simulated. We consider two theories, $N_f=0$ QCD and QCD with $N_f=2$ charm quarks in the sea. The charm sea effects (due to two charm quarks) are estimated comparing the results obtained in these two theories, after matching them and taking the continuum limit. The absence of light quarks allows us to simulate the $N_f=2$ theory at lattice spacings down to $0.023$ fm that are crucial for reliable continuum extrapolations. We find that sea charm quark effects are below $1%$ for the decay constants of charmonium. Our results show that decoupling of charm works well up to energies of about $500$ MeV. We also compute the derivatives of the decay constants and meson masses with respect to the charm mass. For these quantities we again do not see a significant dynamical charm quark effect, albeit with a lower precision. For mesons made of a charm quark and a heavy antiquark, whose mass is twice that of the charm quark, sea effects are only about $0.1%$ in the ratio of vector to pseudoscalar masses.
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