name

Shigemi Ohta

refid

22241

email

shigemi.ohta@kek.jp

title

Domain wall fermion calculation of the nucleon axial vector coupling g_A

collaboration

Tom Blum, Shoichi Sasaki and RIKEN-BNL-Columbia-KEK collaboration

abstract

\documentclass{article}

\title{Domain wall fermion calculation of the nucleon axial vector
coupling $g_A$}

\author{Tom Blum, Shoichi Sasaki, and Shigemi Ohta}

\date{}

\begin{document}

\maketitle

We present a calculation, using domain wall fermions (DWF), of
the iso-vector axial charge of the nucleon $g_{_{A}}$.
In contrast to naive expectations, both
quenched and full QCD lattice calculations with Wilson fermions
underestimate $g_{_{A}}$ by about 25 \%. plausible explanation for this
discrepancy is the uncertainty in the axial current renormalization
$Z_{_{A}}$ which relates the lattice value of $g_{_{A}}$
to the continuum value,
$g_{_{A}} = Z_{_{A}} g_{_{A}}^{\rm lattice}$.
The estimates for
$Z_{A}$ with Wilson fermions that have been used are not well controlled.
In lattice calculations with
DWF the ratio of $g_{_{A}}^{\rm lattice}/g_{_{V}}^{\rm lattice}$
directly yields the continuum value.
This is because DWF
satisfy the relation $Z_{_A} = Z_{_V}$ to a high degree of accuracy
by maintaining nearly exact chiral symmetry at finite lattice spacing, as
has been demonstrated non-perturbatively by the RIKEN-BNL-Columbia-KEK
collaboration. Note also that the conserved vector current assures the
relation $Z_{_{V}} g_{_{V}}^{\rm lattice}=1$. In this talk, we present a
preliminary result of our calculation of $g_{_{A}}$ obtained by this
method. We will also discuss a preliminary result for the tensor charge of
the nucleon. We use DWF propagators generated by the
RIKEN-BNL-Columbia-KEK collaboration on
quenched gauge configurations
at \(\beta=6/g^2=6.0\) on a
\(16^3\times 32\times 16\) lattice.

\end{document}

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