Study of the doubly and singly Cabibbo suppressed decays D +→K+π+π- and D s+→K+π+π-

Abstract Using data collected by the high energy photoproduction experiment FOCUS at Fermilab we study the doubly and singly Cabibbo suppressed decays D + and D s + → K + π + π − . Our measurements of Γ ( D + → K + π + π − ) / Γ ( D + → K − π + π + ) = 0.0065 ± 0.0008 ± 0.0004 and Γ ( D s + → K + π + π − ) / Γ ( D s + → K + K − π + ) = 0.127 ± 0.007 ± 0.014 are based on samples of 189 ± 24 D + and 567 ± 31 D s + reconstructed events, respectively. We also present Dalitz plot analyses of the two decay channels; the amplitude analysis of the D s + → K + π + π − mode is performed for the first time.