Search for ${\rm Y}(1S,2S)\to Z_c^{+}{Z}_c^{(\prime )-}$ and $e^{+}{e}^{-}\to Z_c^{+}{Z}_c^{(\prime )-}$ at $\sqrt{s}$ = 10.52, 10.58, and 10.867 GeV

Abstract

The first search for $Z_c$ pair production in ${\rm Y}(1S)$ and ${\rm Y}(2S)$ decays and in $e^{+}{e}^{-}$ annihilation at $\sqrt{s}$ = 10.52, 10.58, and 10.867 GeV is conducted using data collected with the Belle detector at the KEKB asymmetric energy electron-positron collider. No significant signals are observed in any of the studied modes, and the 90\% credibility level upper limits on their product branching fractions in ${\rm Y}(1S)$ and ${\rm Y}(2S)$ decays ($\mathcal{B}({\rm Y}(1S,2S)\to Z_c^{+}{Z}_c^{(\prime )-})\times \mathcal{B}(Z_c^{+}\to {\pi }^{+}+c\bar{c})$ ($c\bar{c}=J/\psi$, ${\chi }_{c1}(1P)$, $\psi (2S)$)) and the product of Born cross section and branching fraction for $e^{+}{e}^{-}\to Z_c^{+}{Z}_c^{(\prime )-}$ ($\sigma (e^{+}{e}^{-}\to Z_c^{+}{Z}_c^{(\prime )-})\times \mathcal{B}(Z_c^{+}\to {\pi }^{+}+c\bar{c})$) at $\sqrt{s}$ = 10.52, 10.58, and 10.867 GeV are determined. Here, $Z_c$ refers to the $Z_c(3900)$ and $Z_c(4200)$ observed in the $\pi J/\psi$ final state, the $Z_{c1}(4050)$ and $Z_{c2}(4250)$ in the $\pi {\chi }_{c1}(1P)$ state, and the $Z_c(4050)$ and $Z_c(4430)$ in the $\pi \psi (2S)$ state.

Comments: 16 pages, 10 figures, 6 tables