Scalar and axial vector matrix elements of proton in quenched QCD: Calculation of both connected and disconnected contributions

Abstract

$\pi$-$N$ $\sigma$ term and proton axial vector matrix elements are calculated including disconnected contributions with a variant wall source method using the Wilson quark action at $\beta =5.7$ in quenched QCD. For the $\sigma$ term, we find ${\sigma }_{disc}/{\sigma }_{conn}=2.35(46)$ and $\sigma =44(6)$MeV--60(9)MeV. The fraction of proton spin carried by quarks is $\Delta \Sigma =\Delta u+\Delta d+\Delta s=+0.638(54)-0.347(46)-0.109(30)=+0.18(10)$.

Comments: 3 pages. Latex source file with two figures as epsf-file. Style file is appended at the end. Contribution to Lattice 94