C-Parameter and Jet Broadening at PETRA Energies

e+e− annihilation data recorded by the JADE detector at PETRA were used to measure the C-parameter for the first time at √ 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, BT and BW . We combined the results on αs with those of our previous study of differential 2jet rate, thrust, and heavy jet mass, obtaining αs(35 GeV) = 0.1448 +0.0117 −0.0070 and αs(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 √ s = 14 and 183 GeV, yielded αs(MZ0) = 0.1177 +0.0035 −0.0034. (1) III. Physikalisches Institut der RWTH Aachen, D-52056 Aachen, Germany contact e-mail: [email protected] (2) for a full list of members of the JADE Collaboration see Reference [1]