# Poster presented by Jochen Viehoff

**Poster Session**
**Topic:** Matrix Elements

### A Lattice Analysis of the Axial Coupling of the Proton in full QCD

**Abstract:** The flavor singlet axial coupling of the proton, $g_A^1$, is calculated in full QCD including the contributions from connected and disconnected diagrams. The simulations were done on SESAM's $16^3\times 32$ lattices at $\beta=5.6$ with $N_f=2$ dynamical Wilson fermions. Improved stochastic estimator techniques with complex $Z(2)$ noise were used for the disconnected diagrams. Large statistical fluctuations for the disconnected contributions dominate the error dominates the error of $g_A^1$. We find after tadpole improved renormalization: $g_A^1=0.20(12)$ which is in agreement with experiments.

Massimo Campostrini,
`campo@mailbox.difi.unipi.it`