E-1 Transitions From The Y'' State And The Fine-Structure Of The Chi-B' States

Using the CUSB-II detector at the Cornell Electron Storage Ring, we have made precision measurements of the electric dipole transition rates from Y" to chi'b, which are in excellent agreement with theory. The fine-structure splitting is found to be M(chi'b2) - M(chi'b1) = 13.5 +/- 0.4 +/- 0.5 MeV and M(chi'b1) - M(chi'b0) = 23.2 +/- 0.7 +/- 0.7 MeV, leading to a ratio R = 0.584 +/- 0.024 +/- 0.02. The fine structure measures the relative contributions of the spin-orbit interaction a = 9.5 +/- 0.2 +/- 0.1 MeV and tensor interaction b = 2.3 +/- 0.1 +/- 0.1 MeV. We also find that the long-range confining potential transforms as a Lorentz scalar.