Observation of D+ → KS0 a0 (980)+ in the Amplitude Analysis of D+ → KS0 π+η

Abstract

We perform for the first time an amplitude analysis of the decay D+→KS0π+η and report the observation of the decay D+→KS0a0(980)+ using 2.93 fb-1 of e+e- collision data taken at a center-of-mass energy of 3.773 GeV with the BESIII detector. As the only W-annihilation-free decay among D to a0(980) pseudoscalar, D+→KS0a0(980)+ is the ideal decay in extracting the contributions of the W-emission amplitudes involving a0(980) and to study the final-state interactions. The absolute branching fraction of D+→KS0π+η is measured to be (1.27±0.04stat±0.03syst)%. The branching fractions of intermediate processes D+→KS0a0(980)+ with a0(980)+→π+η and D+→π+K̄0∗(1430)0 with K̄0∗(1430)0→KS0η are measured to be (1.33±0.05stat±0.04syst)% and (0.14±0.03stat±0.01syst)%, respectively.