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Register a new userNPR determination of quark masses from the HISQ action
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Authors
Andrew T. Lytle
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I report on a calculation of bilinear Z-factors needed for determining Z_m using non-perturbative renormalization (NPR) on n_f=2+1+1 HISQ ensembles. RI/MOM and RI/SMOM schemes are studied. These will provide an independent determination of quark masses in addition to other methods being used by the HPQCD collaboration.
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We present a progress report on our calculation of the decay constants $f_B$ and $f_{B_s}$ from lattice-QCD simulations with highly-improved staggered quarks. Simulations are carried out with several heavy valence-quark masses on $(2+1+1)$-flavor ensembles that include charm sea quarks. We include data at six lattice spacings and several light sea-quark masses, including an approximately physical-mass ensemble at all but the smallest lattice spacing, 0.03 fm. This range of parameters provides excellent control of the continuum extrapolation to zero lattice spacing and of heavy-quark discretization errors. Finally, using the heavy-quark effective theory expansion we present a method of extracting from the same correlation functions the charm- and bottom-quark masses as well as some low-energy constants appearing in the heavy-quark expansion.
Some algorithmic details of our $N_f=2+1$ QCD mixed action simulations with overlap valence and improved Wilson sea quarks are presented.
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HPQCD collaboration: MILC collaboration: UKQCD collaboration: C.n Aubin
, C. Bernard
, C. Davies
2004
We compute the strange quark mass $m_s$ and the average of the $u$ and $d$ quark masses $hat m$ using full lattice QCD with three dynamical quarks combined with experimental values for the pion and kaon masses. The simulations have degenerate $u$ and $d$ quarks with masses $m_u=m_dequiv hat m$ as low as $m_s/8$, and two different values of the lattice spacing. The bare lattice quark masses obtained are converted to the $msbar$ scheme using perturbation theory at $O(alpha_s)$. Our results are: $m_s^msbar$(2 GeV) = 76(0)(3)(7)(0) MeV, $hat m^msbar$(2 GeV) = 2.8(0)(1)(3)(0) MeV and $m_s/hat m$ = 27.4(1)(4)(0)(1), where the errors are from statistics, simulation, perturbation theory, and electromagnetic effects, respectively.
We present results for the light quark masses for the Wilson quark action obtained with the PCAC relation for the one-link extended axial vector current in quenched QCD at $beta=5.9-6.5$. This method leads to a remarkable improvement of scaling behavior of the light quark masses compared to the conventional method. We obtain ${bar m}_l=3.87(37)$MeV for the averaged up and down quark mass and ${bar m}_s=97(9)$MeV for the strange quark mass in the ${barMS}$ scheme at $mu=2$GeV.
We study the lattice spacing dependence, or scaling, of physical quantities using the highly improved staggered quark (HISQ) action introduced by the HPQCD/UKQCD collaboration, comparing our results to similar simulations with the asqtad fermion action. Results are based on calculations with lattice spacings approximately 0.15, 0.12 and 0.09 fm, using four flavors of dynamical HISQ quarks. The strange and charm quark masses are near their physical values, and the light-quark mass is set to 0.2 times the strange-quark mass. We look at the lattice spacing dependence of hadron masses, pseudoscalar meson decay constants, and the topological susceptibility. In addition to the commonly used determination of the lattice spacing through the static quark potential, we examine a determination proposed by the HPQCD collaboration that uses the decay constant of a fictitious unmixed s bar s pseudoscalar meson. We find that the lattice artifacts in the HISQ simulations are much smaller than those in the asqtad simulations at the same lattice spacings and quark masses.
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