The rates for magnetic dipole (M1) transitions Υ(nS)→ηb(n′S) + γ, n′≤n are compared. The photon energies for allowed (n′ = n) M1 transitions are very small, so hindered (n′<n) transitions could be more favorable for discovering the ηb(1S,2S). The question then arises whether Υ(2S) or Υ(3S) is a better source of ηb(1S). Whereas one nonrelativistic model favors ηb(1S) production from Υ(2S), this advantage is lost when relativistic corrections are taken into account, and is not common to all sets of wave functions even in the purely nonrelativistic limit. Thus the prospects for discovering ηb(1S) in Υ(3S) radiative decays could be comparable to those in Υ(2S) decays. We also discuss a suggestion for discovering ηb via Υ(35) →b(1P1)ππ followed by hb→ηbγ.

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Journal Physical Review D
Godfrey, S, & Rosner, J.L. (Jonathan L.). (2001). Production of the ηb(nS) states. Physical Review D, 64(7). doi:10.1103/PhysRevD.64.074011