Measurement of the Direct Photon Spectrum in Upsilon (1S) Decays
Using data taken with the CLEO II detector at the Cornell Electron Storage Ring, the authors have determined the ratio of branching fractions: R{sub {gamma}} {triple_bond} {Gamma}({Upsilon}(1S) {yields} {gamma}gg)/{Gamma}({Upsilon}(1S) {yields} ggg) = (2.75 {+-} 0.04(stat.) {+-} 0.15(syst.))%. From this ratio, the authors have determined the QCD scale parameter {Lambda}{sub {ovr MS}} (defined in the modified minimal subtraction scheme) to be {Lambda}{sub {ovr MS}} = 233 {+-} 11 {+-} 59 MeV, from which they determine a value for the strong coupling constant {alpha}{sub s}(M{sub {Upsilon}(1S)}) = 0.163 {+-} 0.002 {+-} 0.014, or {alpha}{sub s}(M{sub Z}) = 0.110 {+-} 0.001 {+-} 0.007.
- Research Organization:
- SLAC National Accelerator Lab., Menlo Park, CA (United States)
- Sponsoring Organization:
- USDOE Office of Science (US)
- DOE Contract Number:
- AC03-76SF00515
- OSTI ID:
- 813125
- Report Number(s):
- SLAC-PUB-9840; TRN: US0303666
- Resource Relation:
- Other Information: PBD: 16 May 2003
- Country of Publication:
- United States
- Language:
- English
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