Amplitude analysis and branching fraction measurement of the decay D⁺ → K_S⁰ π⁺ π⁰ π⁰

Using 2.93 fb−1 of e+ e− collision data collected with the BESIII detector at the center-of-mass energy 3.773 GeV, we perform the first amplitude analysis of the decay D+ → KS0 π+ π0 π0 and determine the relative magnitudes and phases of different intermediate processes. The absolute branching fraction of D+ → KS0 π+ π0 π0 is measured to be (2.888 ± 0.058stat. ± 0.069syst.)%. The dominant intermediate processes are D+ → KS0 a 1(1260)+(→ ρ+ π0) and D+ → K¯*0 ρ+, with branching fractions of (8.66 ± 1.04stat. ± 1.39syst.) × 10−3 and (9.70 ± 0.81stat. ± 0.53syst.) × 10−3, respectively.