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Observation of the bottomonium ground state in the decay Upsilon(3S)-->gammaetab |
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| Authors: | Aubert B Bona M Karyotakis Y Lees J P Poireau V Prencipe E Prudent X Tisserand V Garra Tico J Grauges E Lopez L Palano A Pappagallo M Eigen G Stugu B Sun L Abrams G S Battaglia M Brown D N Cahn R N Jacobsen R G Kerth L T Kolomensky Yu G Lynch G Osipenkov I L Ronan M T Tackmann K Tanabe T Hawkes C M Soni N Watson A T Koch H Schroeder T Walker D Asgeirsson D J Fulsom B G Hearty C Mattison T S McKenna J A Barrett M Khan A Blinov V E Bukin A D Buzykaev A R Druzhinin V P Golubev V B Onuchin A P Serednyakov S I Skovpen Yu I Solodov E P Todyshev K Yu Bondioli M Curry S Eschrich I Kirkby D |
| Institution: | Laboratoire de Physique des Particules, IN2P3/CNRS et Université de Savoie, F-74941 Annecy-Le-Vieux, France. |
| Abstract: | We report the results of a search for the bottomonium ground state etab(1S) in the photon energy spectrum with a sample of (109+/-1) million of Upsilon(3S) recorded at the Upsilon(3S) energy with the BABAR detector at the PEP-II B factory at SLAC. We observe a peak in the photon energy spectrum at Egamma=921.2(-2.8)+2.1(stat)+/-2.4(syst) MeV with a significance of 10 standard deviations. We interpret the observed peak as being due to monochromatic photons from the radiative transition Upsilon(3S)-->gammaetab(1S). This photon energy corresponds to an etab(1S) mass of 9388.9(-2.3)+3.1(stat)+/-2.7(syst) MeV/c2. The hyperfine Upsilon(1S)-etab(1S) mass splitting is 71.4(-3.1)+2.3(stat)+/-2.7(syst) MeV/c2. The branching fraction for this radiative Upsilon(3S) decay is estimated to be 4.8+/-0.5(stat)+/-1.2(syst)]x10(-4). |
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