Experimental Evidence for a Light and Broad Scalar Resonance in D+ --> π-π+π+ Decay

From a sample of 1172+/-61 D⁺-->π^-π⁺π⁺ decays, we find γ\(D⁺-->π^- π⁺π⁺\)/γ\(D⁺-->K^-π⁺π⁺\) = 0.0311+/-0.0018^+0.0016_-0.0026. Using a coherent amplitude analysis to fit the Dalitz plot of these decays, we find strong evidence that a scalar resonance of mass 478⁺²⁴_-23+/-17 MeV/c² and width 324⁺⁴²_-40+/-21 MeV/c² accounts for approximately half of all decays.