Production and Decay of ${\Xi }_c^0$ at BABAR

Using $116.1{\mathrm{fb}}^{-1}$ of data collected by the BABAR detector, we present an analysis of ${\Xi }_c^0$ production in $B$ decays and from the $c\overline{c}$ continuum, with the ${\Xi }_c^0$ decaying into ${\Omega }^{-}{K}^{+}$ and ${\Xi }^{-}{\pi }^{+}$ final states. We measure the ratio of branching fractions $\mathcal{B}({\Xi }_c^0\to {\Omega }^{-}{K}^{+})/\mathcal{B}({\Xi }_c^0\to {\Xi }^{-}{\pi }^{+})$ to be $0.294\pm 0.018\pm 0.016$, where the first uncertainty is statistical and the second is systematic. The ${\Xi }_c^0$ momentum spectrum is measured on and 40 MeV below the ${\rm Y}(4S)$ resonance. From these spectra the branching fraction product $\mathcal{B}(B\to {\Xi }_c^{0}X)\times \mathcal{B}({\Xi }_c^0\to {\Xi }^{-}{\pi }^{+})$ is measured to be $(2.11\pm 0.19\pm 0.25)\times {10}^{-4}$, and the cross-section product $\sigma (e^{+}{e}^{-}\to {\Xi }_c^{0}X)\times \mathcal{B}({\Xi }_c^0\to {\Xi }^{-}{\pi }^{+})$ from the continuum is measured to be $(388\pm 39\pm 41)\mathrm{fb}$ at a center-of-mass energy of 10.58 GeV.

Figure 1

Invariant mass distributions for ${\Xi }_c^0$ candidates in $116.1{\mathrm{fb}}^{-1}$ of data, for (a) ${\Xi }^{-}{\pi }^{+}$, and (b) ${\Omega }^{-}{K}^{+}$.

Figure 2

The $p^{*}$ spectrum measurements. In (a)  the $p^{*}$ spectrum of ${\Xi }_c^0$ decaying via ${\Xi }^{-}{\pi }^{+}$ is shown for the on-resonance data sample. In (b) the on-resonance and off-resonance data samples are shown together, with the off-resonance normalization scaled to account for the difference in integrated luminosity and cross section. In each plot, the inner error bars give the statistical uncertainty and the outer error bars give the sum in quadrature of the statistical and systematic uncertainties. The vertical line at $2.15\mathrm{GeV}/c$ in (b) shows the kinematic cutoff for ${\Xi }_c^0$ produced in $B$ decays at BABAR. Note that the vertical axes show events per unit $p^{*}$, not events in each $p^{*}$ bin as given in Table 1.