Observation of h_b(1P)->eta_b(1S)gamma
Abstract
We report the first observation of the radiative transition h_b(1P)->eta_b(1S)gamma, where the h_b(1P) is produced in Upsilon(5S)->h_b(1P)pi+pi- dipion transitions. We measure the eta_b(1S) mass to be (9401.0+-1.9+1.4-2.4)MeV/c^2 with a width of (12.4+5.5-4.6+11.5-3.4)MeV and a decay branching fraction of BF[h_b(1P)->eta_b(1S)gamma]=(49.8+-6.8+10.9-5.2)%. The measured eta_b(1S) mass corresponds to a hyperfine splitting of (59.3+-1.9+2.4-1.4)MeV/c^2. This value deviates significantly from the current world average obtained from measurements of Upsilon(3S)->eta_b(1S)gamma and Upsilon(2S)->eta_b(1S)gamma reactions. We also report updated results for the h_b(1P) mass (9899.0+-0.4+-1.0)MeV/c^2 and its hyperfine splitting (0.8+-1.1)MeV/c^2. These measurements are performed using a 121.4fb^-1 data sample collected at the peak of the Upsilon(5S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider.
Keywords
Cite
@article{arxiv.1110.3934,
title = {Observation of h_b(1P)->eta_b(1S)gamma},
author = {BELLE Collaboration},
journal= {arXiv preprint arXiv:1110.3934},
year = {2012}
}
Comments
Prepared for International Workshop on Heavy Quarkonium 2011 (QWG 2011), GSI, Darmstadt, Germany, 4-7 Oct 2011