Measurement of the longitudinal cross-section using the direction of the thrust axis in hadronic events at LEP Academic Article uri icon


  • In the process e + e − →hadrons, one of the effects of gluon emission is to modify the (1+cos 2 θ ) form of the angular distribution of the thrust axis, an effect which may be quantified by the longitudinal cross-section . Using the OPAL detector at LEP, we have determined the longitudinal to total cross-section ratio to be σ L / σ tot =0.0127±0.0016±0.0013 at the parton level, in good agreement with the expectation of QCD computed to O (α s 2 ) . Comparisons at the hadron level with Monte Carlo models are presented. The dependence of the longitudinal cross-section on the value of thrust has also been studied, and provides a new test of QCD.


publication date

  • January 1, 1998