  By calculating various disk level S-matrix elements and studying in details
their momentum expansions, we have extracted some of the couplings in tachyon
DBI action and Wess-Zumino terms of the non-BPS branes, and their higher
derivative corrections. In particular, we have found that there is exact
consistency between field theory and string theory tachyon pole of S-matrix
element of one RR and three tachyons provided that one takes into account the
fact that the tachyon vertex operator in 0 picture to be along the Pauli matrix
$\sigma_1$ whereas the tachyon in -1 picture to be along the $\sigma_2$
direction. This internal CP factors should be included in the tachyon DBI part
of the effective action.
