Evidence of a new excited charmed baryon decaying to $\hat{I}{\pounds }_c(2455{)}^{0,++}\ddot{I}{€}^{\pm }$

Abstract

We present the study of ${\bar{B}}^0\to \hat{I}{\pounds }_c(2455{)}^{0,++}\ddot{I}{€}^{\pm }\bar{p}$ decays based on $772\times 10^6$ $B\bar{B}$ events collected with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. The $\hat{I}{\pounds }_c(2455{)}^{0,++}$ candidates are reconstructed via their decay to $\hat{I}{›}_c^{+}\ddot{I}{€}^{\mp }$ and $\hat{I}{›}_c^{+}$ decays to $p{K}^{-}\ddot{I}{€}^{+},p{K}_S^0,$ and $\hat{I}›\ddot{I}{€}^{+}$ final states. The corresponding branching fractions are measured to be $\mathcal{B}({\bar{B}}^0\to \hat{I}{\pounds }_c(2455{)}^0\ddot{I}{€}^{+}\bar{p})=(1.09\pm 0.06\pm 0.07)\times 10^{-4}$ and $\mathcal{B}({\bar{B}}^0\to \hat{I}{\pounds }_c(2455{)}^{++}\ddot{I}{€}^{-}\bar{p})=(1.84\pm 0.11\pm 0.12)\times 10^{-4}$, which are consistent with the world average values with improved precision. A new structure is found in the $M_{\hat{I}{\pounds }_c(2455{)}^{0,++}\ddot{I}{€}^{\pm }}$ spectrum with a significance of $4.2\ddot{I}ƒ$ including systematic uncertainty. The structure is possibly an excited $\hat{I}{›}_c^{+}$ and is tentatively named $\hat{I}{›}_c(2910{)}^{+}$. Its mass and width are measured to be $(2913.8\pm 5.6\pm 3.8)$ MeV/$c^2$ and $(51.8\pm 20.0\pm 18.8)$ MeV, respectively. The products of branching fractions for the $\hat{I}{›}_c(2910{)}^{+}$ are measured to be $\mathcal{B}({\bar{B}}^0\to \hat{I}{›}_c(2910{)}^{+}\bar{p})\times \mathcal{B}(\hat{I}{›}_c(2910{)}^{+}\to \hat{I}{\pounds }_c(2455{)}^0\ddot{I}{€}^{+})=(9.5\pm 3.6\pm 1.6)\times 10^{-6}$ and $\mathcal{B}({\bar{B}}^0\to \hat{I}{›}_c(2910{)}^{+}\bar{p})\times \mathcal{B}(\hat{I}{›}_c(2910{)}^{+}\to \hat{I}{\pounds }_c(2455{)}^{++}\ddot{I}{€}^{-})=(1.24\pm 0.35\pm 0.10)\times 10^{-5}$. Here, the first and second uncertainties are statistical and systematic, respectively.

7 pages, 3 figures, 1 table; accepted for publication as a Letter in Physical Review Letters