Amplitude analysis and branching-fraction measurement of D s + → K S 0 π + π 0 $$ {D}_s^{+}\to {K}_S^0{\pi}^{+}{\pi}^0 $$

By using 6.32 fb−1 of data collected with the BESIII detector at center-of-mass energies between 4.178 and 4.226 GeV, we perform an amplitude analysis of the decay $$ {D}_s^{+}\to {K}_S^0{\pi}^{+}{\pi}^0 $$ and determine the relative fractions and phase differences of different intermediate processes, which include $$ {K}_S^0\rho $$ (770)+, $$ {K}_S^0\rho $$ (1450)+, K*(892)0π+, K*(892)+π0, and K*(1410)0π+. With the detection efficiency based on the amplitude analysis results, the absolute branching fraction is measured to be $$ \mathrm{\mathcal{B}}\left({D}_s^{+}\to {K}_S^0{\pi}^{+}\pi 0\right)=\left(5.43\pm {0.30}_{\mathrm{stat}}\pm {0.15}_{\mathrm{syst}}\right)\times {10}^{-3} $$ .