2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/222880By 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 $σ_1$ whereas the tachyon in -1 picture to be along the $σ_2$ direction. This internal CP factors should be included in the tachyon DBI part of the effective action.26 pages, latex file; V5: a missing term in the modified tachyon DBI action addedHigh Energy Physics - Theorytext