Multi-channel joint analysis of the exotic charmonium-like state $T_{c\bar{c}}(4020)$

Abstract

This paper reports the first multi-channel joint analysis to identify the properties of the exotic charmonium-like state $T_{c\bar{c}}(4020)$ via the electron-positron annihilation process $e^{+}{e}^{-}\to \ddot{I}{€}^{+}{T}_{c\bar{c}}(4020{)}^{-}+c.c$. A partial wave analysis is performed simultaneously in three decay channels $T_{c\bar{c}}(4020{)}^{-}\to D^{\ast 0}{D}^{\ast -}$, $\ddot{I}{€}^{-}J/\ddot{I}ˆ$, and $\ddot{I}{€}^{-}{h}_c$, based on data samples taken at $\sqrt{s}=4.395$ and $4.416\mathrm{GeV}$ with an integrated luminosity of $1598.9{\mathrm{pb}}^{-1}$ collected with the BESIII detector operating on the BEPCII collider. For the first time, the spin-parity of the $T_{c\bar{c}}(4020{)}^{-}$ is determined to be $J^P=1^{+}$ with a significance $11.7\ddot{I}ƒ$. Pole positions are extracted on the Riemann sheets with three branch points in the complex energy plane. Furthermore, the relative branching fractions are obtained as $\mathcal{B}[T_{c\bar{c}}(4020{)}^{-}\to \ddot{I}{€}^{-}J/\ddot{I}ˆ]/\mathcal{B}[T_{c\bar{c}}(4020{)}^{-}\to D^{\ast 0}{D}^{\ast -}]=(3.6\pm 0.6\pm 1.6)\times 10^{-3}$ and $\mathcal{B}[T_{c\bar{c}}(4020{)}^{-}\to \ddot{I}{€}^{-}{h}_c]/\mathcal{B}[T_{c\bar{c}}(4020{)}^{-}\to D^{\ast 0}{D}^{\ast -}]=(8.9\pm 1.3\pm 2.3)\times 10^{-2}$, where the first uncertainties are statistical, and the second are systematic.