Momentum distribution of charged particles in jets in dijet events and comparison to perturbative QCD predictions

Abstract

Inclusive momentum distributions of charged particles are measured in dijet events. Events were produced at the AMY detector with a centre of mass energy of 60 GeV. Our results were compared, on the one hand to those obtained from other e ⁺e ⁻, ep as well as CDF data, and on the other hand to the perturbative QCD calculations carried out in the framework of the modified leading log approximation (MLLA) and assuming local parton–hadron duality (LPHD). A fit of the shape of the distributions yields Q _eff = 263±13 MeV for the AMY data. In addition, a fit to the evolution of the peak position with dijet mass using all data from different experiments gives Q _eff = 226±18 MeV. Next, α _s was extracted using the shape of the distribution at the Z ⁰ scale, with a value of 0.118 ± 0.013. This is consistent, within the statistical errors, with many accurate measurements. We conclude that it is the success of LPHD + MLLA that the extracted value of α _s is correct. Possible explanations for all these features will be presented in this paper.

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