Published October 1985 | Version v1
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The χb states in exclusive radiative decay of the Υ(2S)

  • 1. Nationaal Inst. voor Kernfysica en Hoge-Energiefysica (NIKHEF), Nijmegen (Netherlands)
  • 2. Katholieke Univ. Nijmegen (Netherlands)
  • 3. Harvard Univ., Cambridge, MA (USA)
  • 4. Cape Town Univ. (South Africa)
  • 5. Princeton Univ., NJ (USA)
  • 6. Stanford Linear Accelerator Center, CA (USA)
  • 7. Stanford Univ., CA (USA). Dept. of Physics
  • 8. Carnegie-Mellon Univ., Pittsburgh, PA (USA)
  • 9. Florence Univ. (Italy)
  • 10. Istituto Nazionale di Fisica Nucleare, Florence (Italy)
  • 11. California Inst. of Tech., Pasadena (USA)
  • 12. Erlangen-Nuernberg Univ., Erlangen (Germany, F.R.)
  • 13. Hamburg Univ. (Germany, F.R.). 1. Inst. fuer Experimentalphysik
  • 14. Institute of Nuclear Physics, Krakow (Poland)
  • 15. Wuerzburg Univ. (Germany, F.R.)
  • 16. Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany, F.R.)

Description

The Crystal Ball detector at DORIS II has been used to study radiative decays of the Υ(2S) resonance. We report on the analysis of the exclusive channel Υ(2S) → γχb, χb → γΥ(1S) → e+e- or μ+μ-. We detect two χb states by observing two monochromatic photon lines at energies (107.0 ± 1.1 ± 1.3) MeV and (131.7 ± 0.9 ± 1.3) MeV respectively. The product branching ratios BR [Υ(2S) → γχb] x BR [χb → γΥ(1S)] are (1.6 ± 0.3 ± 0.2)% for the first state and (2.1 ± 0.3 ± 0.3)% for the second. For the product branching ratio of the third χb state, which has been observed in inclusive measurements, we find an upper limit of 0.2% (90% C.L.). Combining our results with inclusive measurements, branching ratios for χb → γΥ(1S) are derived. Using theoretical estimates for the radiative widths of the χb states, we determine their hadronic widths; the results are compared with QCD predictions. (orig.)

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Imprint Pagination
36 p.
Report number
DESY--85-019