Research Papers in Physics and Astronomy


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Published by American Physical Society. Phys. Rev. D 59, 032003 (1999). Copyright © 1999 American Physical Society. Permission to use.


We present new measurements of photon energies and branching fractions for the radiative transitions Υ(2S) → γχb(J=0,1,2)(1P). The masses of the χb states are determined from the measured radiative photon energies. The ratio of mass splittings between the χb substates, r ≡ [(MJ=2 -MJ=1)/( MJ=1 - MJ=0), with M the χb mass, provides information on the nature of the bb̅ confining potential. We find r(1P)=0.542 ±0.022±0.024. This value is somewhat lower than the previous world average, but more consistent with the theoretical expectation that r(1P) < r(2P); i.e., that this mass splitting ratio is smaller for the χb (1P) states than for the χb (2P) states.

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