Production of singlet P-wave $c \bar c$ and $b \bar b$ states

Abstract

No spin-singlet $b \bar b$ quarkonium state has yet been observed. In this paper we discuss the production of the singlet P-wave $b\bar{b}$ and $c\bar{c}$ $^1P_1$ states $h_b$ and $h_c$. We consider two possibilities. In the first the $^1P_1$ states are produced via the electromagnetic cascades $\ups(3S) \to \eta_b(2S) + \gamma \to h_b + \gamma \gamma \to \eta_b +\gamma\gamma\gamma $ and $\psi'\to \eta_c' + \gamma \to h_c + \gamma \gamma \to \eta_c + \gamma\gamma\gamma$. A more promising process consists of single pion transition to the $^1P_1$ state followed by the radiative transition to the $1^1S_0$ state: $\ups(3S)\to h_b + \pi^0 \to \eta_b + \pi^0 +\gamma$ and $\psi' \to h_c + \pi^0 \to \eta_c + \pi^0 +\gamma$. For a million $\ups(3S)$ or $\psi'$'s produced we expect these processes to produce several hundred events.