Experimental evidence for a light and broad scalar resonance in $D^+\to π^-π^+π^+$ decay

From a sample of $ 1172 \pm 61 $ $ D^+ \to \pi^- \pi^+ \pi^+ $ decay, we find $ \Gamma (D^+ \to \pi^- \pi^+ \pi^+) / \Gamma (D^+ \to K^- \pi^+ \pi^+) = 0.0311 \pm 0.0018 ^{+0.0016}_{-0.0026} $. Using a coherent amplitude analysis to fit the Dalitz plot of this decays, we find strong evidence that a scalar resonance of mass $478^{+24}_{-23} \pm 17 $ MeV/$c^2$ and width $324^{+42}_{-40} \pm 21 $ MeV/$c^2$ accounts for approximately half of all decays.