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Phys. Rev. D 55, 5273–5281 (1997)

Measurement of the direct photon spectrum in Υ(1S) decays

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B. Nemati et al. (CLEO Collaboration)
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Received 30 October 1996; published in the issue dated 1 May 1997

Using data taken with the CLEO II detector at the Cornell Electron Storage Ring, we have determined the ratio of branching fractions: RγΓ(Υ(1S)→γgg)/Γ(Υ(1S)→ggg)=[2.75±0.04(stat)±0.15(syst)]%. From this ratio, we have determined the QCD scale parameter ΛMS̅ (defined in the modified minimal subtraction scheme) to be ΛMS̅ =233±11±59 MeV, from which we determine a value for the strong coupling constant αs(MΥ(1S))=0.163±0.002±0.014, or αs(MZ)=0.110±0.001±0.007.

© 1997 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevD.55.5273
DOI:
10.1103/PhysRevD.55.5273
PACS:
13.40.Dk, 13.25.Gv, 14.40.Gx