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Register a new userThe $Delta_{mix}$ parameter in the overlap on domain-wall mixed action
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A direct calculation of the mixed-action parameter $Delta_{mix}$ with valence overlap fermions on a domain-wall fermion sea is presented. The calculation is performed on four ensembles of the 2+1-flavor domain-wall gauge configurations: $24^3 times 64$ ($a m_l= 0.005$, $a=0.114fm$) and $32^3 times 64$ ($a m_l = 0.004, 0.006, 0.008$, $a=0.085fm$). For pion masses close to $300MeV$ we find hbox{$Delta_{mix}=0.030(6)GeV^4$} at $a=0.114fm$ and $Delta_{mix}=0.033(12)GeV^4$ at $a=0.085fm$. The results are quite independent of the lattice spacing and they are significantly smaller than the results for valence domain-wall fermions on Asqtad sea or those of valence overlap fermions on clover sea. Combining the results extracted from these two ensembles, we get $Delta_{mix}=0.030(6)(5)GeV^4$, where the first error is statistical and the second is the systematic error associated with the fitting method.
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We present results of our continuing study on mixed-action hadron spectra and decay constants using overlap valence quarks on MILCs 2+1+1 flavor HISQ gauge configurations. This study is carried out on three lattice spacings, with charm and strange masses tuned to their physical values, and with m_l/m_s = 1/5. We present results of an ongoing determination of the mixed-action parameter Delta_{mix}, which enters into chiral formulae for the masses and decay constants.
We report meson spectra obtained by using valence overlap fermion propagators generated on a background of 2+1 flavor domain wall fermion gauge configurations on 16^3 X 32, 24^3 X 64 and 32^3 X 64 lattices. We use many-to-all correlators with Z3 grid source and low eigenmode substitution which is efficient in reducing errors for the hadron correlators. The preliminary results on meson spectrum, a0 correlators, and charmonium hyperfine splitting for three sea quark masses are reported here.
We have computed the SU(2) Low Energy Constant l5 and the mass splitting between charged and neutral pions from a lattice QCD simulation of nf = 2 + 1 flavors of Domain Wall Fermions at a scale of a-1 = 2.33GeV. Relating l5 to the S parameter in QCD we obtain a value of S(mH=120GeV) = 0.42(7), in agreement with previous determinations. Our result can be compared with the value of S from electroweak precision data which constrains strongly interacting models of new physics like Technicolor. This work in QCD serves as a test for the methods to compute the S parameter with Domain Wall Fermions in theories beyond the Standard Model. We also infer a value for the pion mass splitting in agreement with experiment.
We present renormalization constants of overlap quark bilinear operators on 2+1-flavor domain wall fermion configurations. Both overlap and domain wall fermions have chiral symmetry on the lattice. The scale independent renormalization constant for the local axial vector current is computed using a Ward Identity. The renormalization constants for the scalar, pseudoscalar and vector current are calculated in the RI-MOM scheme. Results in the MS-bar scheme are obtained by using perturbative conversion ratios. The analysis uses in total six ensembles with lattice sizes 24^3x64 and 32^3x64.
We report on a calculation of $B_K$ with domain wall fermion action in quenched QCD. Simulations are made with a renormalization group improved gauge action at $beta=2.6$ and 2.9 corresponding to $a^{-1}approx 2$GeV and 3GeV. Effects due to finite fifth dimensional size $N_5$ and finite spatial size $N_sigma$ are examined in detail. Matching to the continuum operator is made perturbatively at one loop order. We obtain $B_K(mu = 2 GeV)= 0.5746(61)(191)$, where the first error is statistical and the second error represents an estimate of scaling violation and ${cal O}(alpha^2)$ errors in the renormalization factor added in quadrature, as an estimate of the continuum value in the $msbar$ scheme with naive dimensional regularization. This value is consistent, albeit somewhat small, with $B_K(mu = 2 {GeV})= 0.628(42)$ obtained by the JLQCD Collaboration using the Kogut-Susskind quark action. Results for light quark masses are also reported.
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