Perturbative universality in soft particle production b
INFN — Laboratori Nazionali di Frascati, P.O. Box 13, 1-00044, Frascati, Italy
2 TH Division CERN, CH-1211, Geneva 23, Switzerland
3 Max-Planck-Institut für Physik, (Werner-Heisenberg-Institut), Föhringer Ring 6, D-80805, Munich, Germany
Published online: 16 September 2013
The spectrum of partons in a QCD jet becomes independent of the primary energy in the low momentum limit. This follows within the perturbative QCD from the colour coherence in soft gluon branching. Remarkably, the hadrons follow such behaviour closely, suggesting the parton hadron duality picture to be appropriate also for the low momentum particles. More generally, this scaling property holds for particles of low transverse and arbitrary longitudinal momentum, which explains an old experimental observation (“fan invariance”). Further tests of the perturbatively based picture for soft particle production are proposed for three-jet events in e+e− annihilation and di-jet production events in γp, γγ and collisions. They are based upon the difference in the intensity of the soft radiation from primary and gg antennae.
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