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 $\ups(3S) \to η_b(2S) + γ\to h_b + γγ\to η_b +γγγ$ and $ψ'\to η_c' + γ\to h_c + γγ\to η_c + γγγ$. 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: $\ups(3S)\to h_b + π^0 \to η_b + π^0 +γ$ and $ψ' \to h_c + π^0 \to η_c + π^0 +γ$. For a million $\ups(3S)$ or $ψ'$'s produced we expect these processes to produce several hundred events.