C-Parameter and Jet Broadening at PETRA Energies

Abstract

e^+e^- annihilation data recorded by the JADE detector at PETRA were used to measure the C-parameter for the first time at \sqrt{s}= 35 and 44 GeV. The distributions were compared to a resummed QCD calculation. In addition, we applied extended resummed calculations to the total and wide jet broadening variables, B_T and B_W. We combined the results on α_s with those of our previous study of differential 2-jet rate, thrust, and heavy jet mass, obtaining α_s(35 GeV) = 0.1448 +0.0117 -0.0070 and α_s(44 GeV) = 0.1392 +0.0105 -0.0074. Moreover power corrections to the mean values of the observables mentioned above were investigated considering the Milan factor and the improved prediction for the jet broadening observables. Our study, which considered e^+e^- data of five event shape observables between \sqrt{s}= 14 and 183 GeV, yielded α_s(M_{Z^0})=0.1177 +0.0035 -0.0034.