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

TL;DR

This paper systematically studies heavy quarkonium production via Z^0 decays at high-luminosity colliders using NRQCD, providing analytic expressions and estimating event yields for different quarkonium states.

Contribution

It introduces improved trace technology for analytic amplitude derivation and estimates heavy quarkonium production rates through Z^0 decays at colliders.

Findings

Calculated decay widths for various quarkonium states.

Estimated millions of heavy quarkonium events per year at colliders.

Provided analytic expressions useful for future decay channel analyses.

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.