Amplitude analysis and branching fraction measurement of the decay Ds+ → K + π + π −

Using 6.32 fb−1 of e+e− collision data collected at the center-of-mass energies between 4.178 and 4.226 GeV with the BESIII detector, we perform an amplitude analysis of the decay Ds+→ K+π+π− and determine the amplitudes of the various intermediate states. The absolute branching fraction of Ds+→ K+π+π− is measured to be (6.11 ± 0.18stat.± 0.11syst.) × 10−3. The branching fractions of the dominant intermediate processes Ds+→ K+ρ0, ρ0→ π+π− and Ds+→ K*(892)0π+, K*(892)0→ K+π− are determined to be (1.96 ± 0.19stat.± 0.23syst.) × 10−3 and (1.85 ± 0.12stat.± 0.13syst.) × 10−3, respectively. The intermediate resonances f0(500), f0(980), and f0(1370) are observed for the first time in this channel. [Figure not available: see fulltext.]