Study of the Exclusive Initial-State Radiation Production of the $D \bar D$ System

Abstract

A study of exclusive production of the $D \bar D$ system through initial-state r adiation is performed in a search for charmonium states, where $D=D^0$ or $D^+$. The $D^0$ mesons are reconstructed in the $D^0 \to K^- π^+$, $D^0 \to K^- π^+ π^0$, and $D^0 \to K^- π^+ π^+ π^-$ decay modes. The $D^+$ is reconstructed through the $D^+ \to K^- π^+ π^+$ decay mode. The analysis makes use of an integrated luminosity of 288.5 fb$^{-1}$ collected by the BaBar experiment. The $D \bar D$ mass spectrum shows a clear $ψ(3770)$ signal. Further structures appear in the 3.9 and 4.1 GeV/$c^2$ regions. No evidence is found for Y(4260) decays to $D \bar D$, implying an up per limit $\frac{\BR(Y(4260)\to D \bar D)}{\BR(Y(4260)\to J/ψπ^+ π^-)} < 7.6$ (95 % confidence level).