5 research outputs found
Update on form factor at zero-recoil using the Oktay-Kronfeld action
We present an update on the calculation of
semileptonic form factor at zero recoil using the Oktay-Kronfeld bottom and
charm quarks on flavor HISQ ensembles generated by the MILC
collaboration. Preliminary results are given for two ensembles with and fm and MeV. Calculations have been done
with a number of valence quark masses, and the dependence of the form factor on
them is investigated on the fm ensemble. The excited state is
controlled by using multistate fits to the three-point correlators measured at
4--6 source-sink separations.Comment: 7 pages and 4 figures. Talk at The 36th Annual International
Symposium on Lattice Field Theory - LATTICE201
Chiral symmetry and taste symmetry from the eigenvalue spectrum of staggered Dirac operators
We investigate general properties of the eigenvalue spectrum for improved
staggered quarks. We introduce a new chirality operator
and a new shift operator , which respect the same recursion
relation as the operator in the continuum. Then we show that matrix
elements of the chirality operator sandwiched between two eigenstates of the
staggered Dirac operator are related to those of the shift operator by the Ward
identity of the conserved symmetry of staggered fermion actions. We
perform a numerical study in quenched QCD using HYP staggered quarks to
demonstrate the Ward identity. We introduce a new concept of leakage patterns
which collectively represent the matrix elements of the chirality operator and
the shift operator sandwiched between two eigenstates of the staggered Dirac
operator. The leakage pattern provides a new method to identify zero modes and
non-zero modes in the Dirac eigenvalue spectrum. This method is as robust as
the spectral flow method but requires much less computing power. Analysis using
a machine learning technique confirms that the leakage pattern is universal,
since the staggered Dirac eigenmodes on normal gauge configurations respect it.
In addition, the leakage pattern can be used to determine a ratio of
renormalization factors as a by-product. We conclude that it might be possible
and realistic to measure the topological charge using the Atiya-Singer
index theorem and the leakage pattern of the chirality operator in the
staggered fermion formalism.Comment: 27 pages, 78 figures, 10 tables, references updated, more explanation
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How to identify zero modes for improved staggered fermions
Jeong H, Jwa S, Kim J, et al. How to identify zero modes for improved staggered fermions. In: 35th International Symposium on Lattice Field Theory (Lattice 2017). 2017.We present results of the eigenvalue spectrum for the staggered Dir\"ac
operator obtained using a modified Lanczos algorithm. We identify zero modes
and non-zero modes. We derive the chiral Ward identity derived from the
conserved symmetry, and check it numerically. This is the first step
toward construction of an improved method to identify zero modes reliably with
staggered fermions