Precision Determination of the $D^0$ Mass

A precision measurement of the $D^0$ meson mass has been made using $\sim 281{\mathrm{pb}}^{-1}$ of $e^{+}{e}^{-}$ annihilation data taken with the CLEO-c detector at the $\psi (3770)$ resonance. The exclusive decay $D^0\to K_S\varphi$ has been used to obtain $M(D^0)=1864.847\pm 0.150(\mathrm{stat})\pm 0.095(\mathrm{syst})\mathrm{MeV}$. This corresponds to $M(D^0{\overline{D}}^{*0})=3871.81\pm 0.36\mathrm{MeV}$, and leads to a well-constrained determination of the binding energy of the proposed $D^0{\overline{D}}^{*0}$ molecule $X(3872)$, as $E_b=0.6\pm 0.6\mathrm{MeV}$.

Figure 1

Upper plot: Invariant mass of the (${\pi }^{+}{\pi }^{-}$) system for $K_S$ decay candidates. The curve shows the fit with the peak shape given by the sum of two Gaussians. Lower plot: Invariant mass of the ($K^{+}{K}^{-}$) system. The curve shows the fit with a Breit-Wigner shape convoluted with a Gaussian shape and a linear background.

Figure 2

Invariant mass of $K_S{K}^{+}{K}^{-}$ system for $D^0\to K_S\varphi$ decay candidates. The curve shows fit results with a Gaussian peak shape and a constant background.

Figure 3

Invariant mass of (${\pi }^{+}{\pi }^{-}$) system for $K_S$ decay candidates from inclusive sample. The curve shows fit results with the peak shape given by the sum of two Gaussians, and a linear background.