First measurements of the absolute branching fraction of $\hat{I}{›}_c(2625{)}^{+}\to \hat{I}{›}_c^{+}\ddot{I}{€}^{+}\ddot{I}{€}^{-}$ and upper limit on $\hat{I}{›}_c(2595{)}^{+}\to \hat{I}{›}_c^{+}\ddot{I}{€}^{+}\ddot{I}{€}^{-}$

Abstract

The absolute branching fraction of the decay $\hat{I}{›}_c(2625{)}^{+}\to \hat{I}{›}_c^{+}\ddot{I}{€}^{+}\ddot{I}{€}^{-}$ is measured for the first time to be $(50.7\pm 5.0_{stat.}\pm 4.9_{syst.})\%$ with 368.48 pb${}^{-1}$ of $e^{+}{e}^{-}$ collision data collected by the BESIII detector at the center-of-mass energies of $\sqrt{s}=4.918$ and $4.950$ GeV. This result is lower than the naive prediction of 67\%, obtained from isospin symmetry, by more than $2\ddot{I}ƒ$, thereby indicating that the novel mechanism referred to as the \textit{threshold effect}, proposed for the strong decays of $\hat{I}{›}_c(2595{)}^{+}$, also applies to $\hat{I}{›}_c(2625{)}^{+}$. This measurement is necessary to obtain the coupling constants for the transitions between $s$-wave and $p$-wave charmed baryons in heavy hadron chiral perturbation theory. In addition, we search for the decay $\hat{I}{›}_c(2595{)}^{+}\to \hat{I}{›}_c^{+}\ddot{I}{€}^{+}\ddot{I}{€}^{-}$. No significant signal is observed, and the upper limit on its branching fraction is determined to be 80.8\% at the 90\% confidence level.

8 pages, 6 figures