Production of a heavy quarkonium with a photon or via ISR at Z peak in e ⁺ e ⁻ collider

Abstract

Considering the possibility to build an e ⁺ e ⁻ collider at the energies around Z-boson resonance with a luminosity so high as L ∝ 10³⁴ cm⁻² s⁻¹ (even higher) and the abilities of a modern synthesis detector, we systematically calculate the exclusive two body processes of the heavy quarkonium production: e ⁺ e ⁻ annihilates into a heavy quarkonium and a photon, involving the initial state radiation (i.e. ISR) cases, at the energies around the Z-boson resonance. Since the couplings of Z-boson to quarks contain an axial vector term as well as a vector one, a charmonium such as J/ψ or η _c or h _c or χ _cJ …, or a bottomonium such as ϒ or η _b or h _b or χ _bJ …, associating with a photon, may be produced respectively via Z-boson annihilation. If we call such a collider with so high luminosity and running around the Z-boson resonance as a Z-factory, then our results obtained here indicate that experimental studies of the various heavy quarkona (their ground and excited states) via the two-body processes at a Z-factory have outstanding advantages, especially, the production of the possible states with quantum numbers J ^PC = 1⁻⁻ via ISR.