Measurement of the direct photon spectrum in {Upsilon}(1S) decays
Using data taken with the CLEO II detector at the Cornell Electron Storage Ring, we have determined the ratio of branching fractions: R{sub {gamma}}{equivalent_to}{Gamma}{bold (}{Upsilon}(1S){r_arrow}{gamma}gg{bold )}/{Gamma}{bold (}{Upsilon}(1S){r_arrow}ggg{bold )}=[2.75{plus_minus}0.04(stat){plus_minus}0.15(syst)]{percent}. From this ratio, we have determined the QCD scale parameter {Lambda}{sub {ovr MS}} (defined in the modified minimal subtraction scheme) to be {Lambda}{sub {ovr MS}}=233{plus_minus}11{plus_minus}59 MeV, from which we determine a value for the strong coupling constant {alpha}{sub s}(M{sub {Upsilon}(1S)})=0.163{plus_minus}0.002{plus_minus}0.014, or {alpha}{sub s}(M{sub Z})=0.110{plus_minus}0.001{plus_minus}0.007. {copyright} {ital 1997} {ital The American Physical Society}
- OSTI ID:
- 562404
- Journal Information:
- Physical Review, D, Vol. 55, Issue 9; Other Information: PBD: May 1997
- Country of Publication:
- United States
- Language:
- English
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