2011/10/18 by Belle Collaboration, BELLE Collaboration
Medicine · Physics and Astronomy · #FOS: Physical sciences #High Energy Physics - Experiment (hep-ex) #Medical Imaging Techniques and Applications #hep-ex
paper · pdf · doi:10.48550/arxiv.1110.3934
Prepared for International Workshop on Heavy Quarkonium 2011 (QWG 2011), GSI, Darmstadt, Germany, 4-7 Oct 2011
arxiv created 2011/10/18 · openalex publication_date 2011/10/18 · arxiv updated 2012/08/27 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We report the first observation of the radiative transition hb(1P)->etab(1S)gamma, where the hb(1P) is produced in Upsilon(5S)->hb(1P)pi+pi- dipion transitions. We measure the etab(1S) mass to be (9401.0+-1.9+1.4-2.4)MeV/c2 with a width of (12.4+5.5-4.6+11.5-3.4)MeV and a decay branching fraction of BF[hb(1P)->etab(1S)gamma]=(49.8+-6.8+10.9-5.2)%. The measured etab(1S) mass corresponds to a hyperfine splitting of (59.3+-1.9+2.4-1.4)MeV/c2. This value deviates significantly from the current world average obtained from measurements of Upsilon(3S)->etab(1S)gamma and Upsilon(2S)->etab(1S)gamma reactions. We also report updated results for the hb(1P) mass (9899.0+-0.4+-1.0)MeV/c2 and its hyperfine splitting (0.8+-1.1)MeV/c2. 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.