Dalitz plot studies of D 0 → K 0 S π + π − decays

The availaible data on the D0 → K0 S π+π− decays are analysed in the framework of the quasi two-body QCD factorization approximation. The annihilation, via Wexchange, amplitudes are added to the weak-decay tree amplitudes. The doubly Cabibbo suppressed parts of the amplitudes are also considered. The strong interactions between the kaon-pion and pion-pion pairs in the S -, Pand D-final states are described in terms of the corresponding form factors. The kaon-pion or pion-pion scalar and vector form factors are constrained by other experimental data. Unitarity, analyticity and chiral symmetry are also used to obtain their functional forms. We go through a minimization procedure to reproduce the K0 S π −, K0 S π + and π+π− effective mass projections of the Dalitz plot distributions. The large number (27) of non-zero amplitudes leads to a large number of parameters. The resulting model distributions and branching fractions are compared to the accurate Belle Collaboration data.