# Consistent measurements of $\alpha_s$ from precise oriented event shape distributions

Abstract : An updated analysis using about 1.5 million events recorded at s=MZ\sqrt{s} = M_Zs ​=MZ​ with the DELPHI detector in 1994 is presented. Eighteen infrared and collinear safe event shape observables are measured as a function of the polar angle of the thrust axis. The data are compared to theoretical calculations in O(αs2){\cal O} (\alpha_s^2)O(αs2​) including the event orientation. A combined fit of αs\alpha_sαs​ and of the renormalization scale xμx_{\mu}xμ​ in O(αs2\cal O(\alpha_s^2O(αs2​) yields an excellent description of the high statistics data. The weighted average from 18 observables including quark mass effects and correlations is αs(MZ2)=0.1174±0.0026\alpha_s(M_Z^2) = 0.1174 \pm 0.0026αs​(MZ2​)=0.1174±0.0026. The final result, derived from the jet cone energy fraction, the observable with the smallest theoretical and experimental uncertainty, is αs(MZ2)=0.1180±0.0006(exp.)±0.0013(hadr.)±0.0008(scale)±0.0007(mass)\alpha_s(M_Z^2) = 0.1180 \pm 0.0006 (exp.) \pm 0.0013 (hadr.) \pm 0.0008 (scale) \pm 0.0007 (mass)αs​(MZ2​)=0.1180±0.0006(exp.)±0.0013(hadr.)±0.0008(scale)±0.0007(mass). Further studies include an αs\alpha_sαs​ determination using theoretical predictions in the next-to-leading log approximation (NLLA), matched NLLA and O(αs2\cal O(\alpha_s^2O(αs2​) predictions as well as theoretically motivated optimized scale setting methods. The influence of higher order contributions was also investigated by using the method of Pad\'{e} approximants. Average αs\alpha_sαs​ values derived from the different approaches are in good agreement. (arXiv)
Document type :
Journal articles
Complete list of metadata

http://hal.in2p3.fr/in2p3-00005207
Contributor : Sylvie Flores Connect in order to contact the contributor
Submitted on : Tuesday, July 4, 2000 - 11:07:17 AM
Last modification on : Sunday, June 26, 2022 - 11:42:39 AM

### Citation

P. Abreu, W. Adam, T. Adye, P. Adzic, Z. Albrecht, et al.. Consistent measurements of $\alpha_s$ from precise oriented event shape distributions. European Physical Journal C: Particles and Fields, Springer Verlag (Germany), 2000, 14, pp.557-584. ⟨10.1007/s100520000354⟩. ⟨in2p3-00005207⟩

Record views