First Measurement of the Decay Asymmetry in the pure W-boson-exchange Decay $\hat{I}{›}_c^{+}\to \hat{I}{ž}^0{K}^{+}$

Abstract

Based on $4.4{\text{fb}}^{-1}$ of $e^{+}{e}^{-}$ annihilation data collected at the center-of-mass energies between $4.60$ and $4.70\text{GeV}$ with the BESIII detector at the BEPCII collider, the pure \textit{W}-boson-exchange decay $\hat{I}{›}_c^{+}\to \hat{I}{ž}^0{K}^{+}$ is studied with a full angular analysis. The corresponding decay asymmetry is measured for the first time to be $\hat{I}{\pm }_{\hat{I}{ž}^0{K}^{+}}=0.01\pm 0.16(stat.)\pm 0.03(syst.)$. This result reflects the non-interference effect between the $S$- and $P$-wave amplitudes. The phase shift between $S$- and $P$-wave amplitudes has two solutions, which are $\hat{I}{´}_p-\hat{I}{´}_s=-1.55\pm 0.25(stat.)\pm 0.05(syst.)\text{rad}$ or $1.59\pm 0.25(stat.)\pm 0.05(syst.)\text{rad}$.