αs determination from event shapes at DELPHI

Recent studies of the strong coupling alpha(s) using the DELPHI detector at LEP [1,2] are reviewed. For the updated analysis of the data at root s = M-Z, a large number of shape observables and their dependence on the event orientation are measured and compared to theoretical calculations in O(alpha(s)(2)). The adjustment of the renormalization scale mu turns out to be of major importance. Applying the so-called physical scale mu(2) = Q(2) leads to a poor description of the data, whereas a combined fit of alpha(s) and the renormalization scale value yields an excellent description of the high statistics data. For these scale values perfect consistency of the fit values of alpha(s)(M-Z) is obtained for all the observables considered within a range of Delta alpha(s) = +/-0.0025. Taking also account of heavy quark mass effects yields the preliminary result alpha(s)(M-Z(2)) = 0.117 +/- 0.003. Additional studies include an alpha(s) determination using theoretical predictions in the next to leading log approximation (NLLA), matched NLLA and O(alpha(s)(2)) predictions as well as theoretically motivated optimized scale setting methods. The running of alpha(s) is measured from the DELPHI data at root s = 130 GeV - 183 GeV. Here an analytical power ansatz for the hadronization corrections is compared with hadronization corrections obtained by using Monte Carlo generators.