Measurement of $J/\ddot{I}ˆ\to {\hat{I}}^3\hat{I}{\cdot }_{\mathrm{c}}$ decay rate and $\hat{I}{\cdot }_{\mathrm{c}}$ parameters at KEDR

Abstract

Using the inclusive photon spectrum based on a data sample collected at the $J/\ddot{I}ˆ$ peak with the KEDR detector at the VEPP-4M $e^{+}{e}^{-}$ collider, we measured the rate of the radiative decay $J/\ddot{I}ˆ\to {\hat{I}}^3\hat{I}{\cdot }_{\mathrm{c}}$ as well as $\hat{I}{\cdot }_{\mathrm{c}}$ mass and width. Taking into account an asymmetric photon lineshape we obtained $\hat{I}{“}_{{\hat{I}}^3\hat{I}{\cdot }_{\mathrm{c}}}^0=2.98\pm 0.18{}_{-0.33}^{+0.15}$ keV, $M_{\hat{I}{\cdot }_{\mathrm{c}}}=2983.5\pm 1.4{}_{-3.6}^{+1.6}$ MeV/$c^2$, $\hat{I}{“}_{\hat{I}{\cdot }_{\mathrm{c}}}=27.2\pm 3.1{}_{-2.6}^{+5.4}$ MeV.

6 pages, 3 figures