Study of excited ${\mathrm{\Xi }}_c$ states decaying into ${\mathrm{\Xi }}_c^0$ and ${\mathrm{\Xi }}_c^{+}$ baryons

Using a data sample of $980{\mathrm{fb}}^{-1}$ of $e^{+}{e}^{-}$ annihilation data taken with the Belle detector operating at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider, we report the results of a study of excited ${\mathrm{\Xi }}_c$ states that decay, via the emission of photons and/or charged pions, into ${\mathrm{\Xi }}_c^0$ or ${\mathrm{\Xi }}_c^{+}$ ground state charmed-strange baryons. We present new measurements of the masses of all members of the ${\mathrm{\Xi }}_c^{\prime }$, ${\mathrm{\Xi }}_c(2645)$, ${\mathrm{\Xi }}_c(2790)$, ${\mathrm{\Xi }}_c(2815)$, and ${\mathrm{\Xi }}_c(2980)$ isodoublets, measurements of the intrinsic widths of those that decay strongly, and evidence of previously unknown transitions.

Figure 1

The distribution of the “pull mass,” i.e. $(M_{\text{measured}}-M({\mathrm{\Xi }}_c^0))/\sigma$, for the ten ${\mathrm{\Xi }}_c^0$ modes used in this analysis. There is an $x_p>0.6$ requirement applied for presentation purposes, but this is not part of the analysis chain.

Figure 2

The distribution of the “pull mass,” i.e. $(M_{\text{measured}}-M({\mathrm{\Xi }}_c^{+}))/\sigma$, for the seven ${\mathrm{\Xi }}_c^{+}$ modes used in this analysis. There is an $x_p>0.6$ requirement applied for presentation purposes, but this is not part of the analysis chain.

Figure 3

Scatter plots of M(${\mathrm{\Xi }}_c\pi \pi$) versus M(${\mathrm{\Xi }}_c(2645))$ for (a) ${\mathrm{\Xi }}_c^0$ and (b) ${\mathrm{\Xi }}_c^{+}$. The lines show the positions of the requirements around the mass peaks used for projections on to the other axis.

Figure 4

The (a) ${\mathrm{\Xi }}_c^0\pi \pi$ and (b) ${\mathrm{\Xi }}_c^{+}\pi \pi$ invariant mass distributions with a cut on ${\mathrm{\Xi }}_c(2645)$ invariant mass of the intermediate state and a scaled momentum requirement of $x_p>0.7$. Both show significant ${\mathrm{\Xi }}_c(2815)$ signals. The fits are described in the text. The dashed lines represent the combinatorial background contributions.

Figure 5

The (a) ${\mathrm{\Xi }}_c^0{\pi }^{+}$ and (b) ${\mathrm{\Xi }}_c^{+}{\pi }^{-}$ invariant mass distributions with a selection on the ${\mathrm{\Xi }}_c\pi \pi$ invariant mass of the ${\mathrm{\Xi }}_c(2815)$ parent state and a scaled momentum cut of $x_p>0.7$ on the parent state. Both show clear ${\mathrm{\Xi }}_c(2645)$ signals. The fits are described in the text. The dashed lines represent the combinatorial background contributions.

Figure 6

The (a) ${\mathrm{\Xi }}_c^0\pi \pi$ and (b) ${\mathrm{\Xi }}_c^{+}\pi \pi$ invariant mass distributions with a cut on ${\mathrm{\Xi }}_c(2645)$ invariant mass of the intermediate state and a scaled momentum cut of $x_p>0.7$. Both show clear ${\mathrm{\Xi }}_c(2980)$ signals. The fits are described in the text. The dashed lines represent the combinatorial background contributions.

Figure 7

The (a) ${\mathrm{\Xi }}_c^0\gamma$ and (b) ${\mathrm{\Xi }}_c^{+}\gamma$ invariant mass distributions. The fits are described in the text. The dashed lines represent the combinatorial background contributions.

Figure 8

The (a) ${\mathrm{\Xi }}_c^{\prime 0}\pi$ and (b) ${\mathrm{\Xi }}_c^{\prime +}\pi$ invariant mass distributions. The fits are described in the text. The dashed lines represent the combinatorial background contributions.

Figure 9

The (a) ${\mathrm{\Xi }}_c^{\prime 0}{\pi }^{+}$ and (b) ${\mathrm{\Xi }}_c^{\prime +}{\pi }^{-}$ invariant mass distributions. The fits are described in the text. The dashed lines represent the combinatorial background contributions.