Determination of the strong coupling constant αs from a study of W production

The total data sample of W events identified in the UA2 experiment has been used to determine the strong coupling constant αs. QCD corrections modify the simple Drell-Yan picture of W production and manifest themselves in the associated production of W bosons with jets. The rate of W events produced in association with a jet is proportional to the strong coupling constant. To measure αs we consider the ratio of the number of W events produced with one jet to the number of W events produced without jets. The value of αs is determined by comparing the measured ratio to the ratio predicted in QCD-models as a function of αs