Calorimetric measurement of the strong coupling constant in electron-positron annihilation at a center-of-mass energy of 91.6 GeV

摘要

In this work, a measurement of the strong coupling constant (alpha)(sub s) in e(sup +)e(sup (minus)) annihilation at a center-of-mass energy of 91.6 GeV is presented. The measurement was performed with the SLD at the Stanford Linear Collider facility located at the Stanford Linear Accelerator Center in California. The procedure used consisted of measuring the rate of hard gluon radiation from the primary quarks in a sample of 9,878 hadronic events. After defining the asymptotic manifestation of partons as 'jets', various phenomenological models were used to correct for the hadronization process. A value for the QCD scale parameter (Lambda)(sub bar MS), defined in the (sub bar MS) renormalization convention with 5 active quark flavors, was then obtained by a direct fit to O((alpha)(sub s)(sup 2)) calculations. The value of (alpha)(sub s) obtained was (alpha)(sub s)(M(sub z0)) = 0.122 (plus minus) 0.004 (sub (minus)0.007) (sup +0.008) where the uncertainties are experimental (combined statistical and systematic) and theoretical (systematic) respectively. Equivalently, (Lambda)(sub bar MS) = 0.28 (sub (minus)0.10)(sup +0.16) GeV where the experimental and theoretical uncertainties have been combined.