Excited Heavy Quarkonium Production via Z^0 Decays at a High Luminosity Collider

Abstract

We present a systematic study of the production of the heavy quarkonium, i.e., $|(c\bar{c})[n] \rangle$ , $|(b\bar{c})[n] \rangle$ (or $|(c\bar{b})[n] \rangle$), and $|(b\bar{b})[n] \rangle$ quarkonium [$|(Q\bar{Q'})[n]\rangle$ quarkonium for short], through $Z^0$ boson semi-exclusive decays with new parameters \cite{lx} for the heavy quarkonium under the framework of the NRQCD, where $[n]$ stands for $n^1S_0$, $n^3S_1$, $n^1P_0$, $n^3P_J$ ($n=1, \cdots, 6$; $J=(0, 1, 2)$). "Improved trace technology" is adopted to derive the simplified analytic expressions at the amplitude level, which shall be useful for dealing with these decay channels. If all higher $|(Q\bar{Q'})[n]\rangle$ quarkonium states decay to the ground state $|(Q\bar{Q'})[1^1S_0]\rangle$ with $100\%$ efficiency via electromagnetic or hadronic interactions, we obtain $\Gamma{(Z^0\to |(c\bar{c})[1^1S_0]\rangle)}=1476$ KeV, $\Gamma{(Z^0\to |(b\bar{c})[1^1S_0]\rangle)}=1485$ KeV, $\Gamma{(Z^0\to |(b\bar{b})[1^1S_0]\rangle)}=127.5$ KeV. At the LHC and ILC with the luminosity ${\cal L}\propto 10^{34}cm^{-2}s^{-1}$, sizable heavy quarkonium events can be produced through $Z^0$ boson decays, i.e., about $5.9~\times10^{5}$ $(c\bar{c})$, $6.0~\times10^{5}$ $(b\bar{c})$ (or $(c\bar{b})$), $5.1~\times10^{4}$ $(b\bar{b})$ events per year can be obtained.