Invariant-mass distributions of $\DtoKpi$ candidates (andcharge conjugates) for $0< \pt< 1 \gev/c$. The left panel displaysthe invariant-mass distribution of all ULS K$\pi$ pairs together with thebackground distribution estimated with the track-rotation technique. The right panel shows the invariant-mass distribution after subtracting the background estimated with the track-rotation technique. The fit function is superimposed.