Evidence of a new excited charmed baryon decaying to ${\mathrm{\Sigma }}_c(2455{)}^{0,++}{\pi }^{\pm }$

We present the study of ${\bar{B}}^0\to {\mathrm{\Sigma }}_c(2455{)}^{0,++}{\pi }^{\pm }\bar{p}$ 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 ${\mathrm{\Sigma }}_c(2455{)}^{0,++}$ candidates are reconstructed via their decay to ${\mathrm{\Lambda }}_c^{+}{\pi }^{\mp }$ and ${\mathrm{\Lambda }}_c^{+}$ decays to $p{K}^{-}{\pi }^{+},p{K}_S^0,$ and $\mathrm{\Lambda }{\pi }^{+}$ final states. The corresponding branching fractions are measured to be $\mathcal{B}({\bar{B}}^0\to {\mathrm{\Sigma }}_c(2455{)}^0{\pi }^{+}\bar{p})=(1.09\pm 0.06\pm 0.07)\times {10}^{-4}$ and $\mathcal{B}({\bar{B}}^0\to {\mathrm{\Sigma }}_c(2455{)}^{++}{\pi }^{-}\bar{p})=(1.84\pm 0.11\pm 0.12)\times {10}^{-4}$, which are consistent with the world average values with improved precision. A new structure is found in the $M_{{\mathrm{\Sigma }}_c(2455{)}^{0,++}{\pi }^{\pm }}$ spectrum with a significance of $4.2\sigma$ including systematic uncertainty. The structure is possibly an excited ${\mathrm{\Lambda }}_c^{+}$ and is tentatively named ${\mathrm{\Lambda }}_c(2910{)}^{+}$. 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 ${\mathrm{\Lambda }}_c(2910{)}^{+}$ are measured to be $\mathcal{B}({\bar{B}}^0\to {\mathrm{\Lambda }}_c(2910{)}^{+}\bar{p})\times \mathcal{B}({\mathrm{\Lambda }}_c(2910{)}^{+}\to {\mathrm{\Sigma }}_c(2455{)}^0{\pi }^{+})=(9.5\pm 3.6\pm 1.6)\times {10}^{-6}$ and $\mathcal{B}({\bar{B}}^0\to {\mathrm{\Lambda }}_c(2910{)}^{+}\bar{p})\times \mathcal{B}({\mathrm{\Lambda }}_c(2910{)}^{+}\to {\mathrm{\Sigma }}_c(2455{)}^{++}{\pi }^{-})=(1.24\pm 0.35\pm 0.10)\times {10}^{-5}$. Here, the first and second uncertainties are statistical and systematic, respectively.