Long-range particle correlations and wavelets

Dremin, I. M.

doi:10.1070/pu2000v043n11abeh000866

Cited by 3 publications

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“…To shorten the presentation, only some of most impressive results have been chosen and no Figures are presented. More complete list with a detailed survey and Figures demonstrating comparison with experiment can be found in the books [1,2] and in recent review papers [3,4,5,6,7].…”

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QCD Physics at Lep

Dremin

2003

Multiparticle Dynamics

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With the advent of LEP we discovered jets and at its last years we learned a lot about intermediate vector bosons. All that strongly supports our belief in QCD. Jet physics is briefly described in this talk. Experimental results are compared with QCD predictions. It is shown that the perturbative QCD has been able not only to describe the existing data but also to predict many bright phenomena.The main process of e + e − -annihilation at LEP looks like two jets moving in the opposite directions. These jets are considered in QCD as (initiated by quarks and collimated) cascades of consecutive emissions of partons each of which produces observed hadrons due to soft confinement. Early days.Jets were discovered in 1975. Their angular collimation was demonstrated in studies of such kinematical properties as sphericity, spherocity, thrust etc. They show that the transverse momenta are small compared to the total momenta if the proper coordinate axes are chosen. The collimation increases with energy increase.The jet axes were defined from these characteristics. It has been shown that the angular (θ) distribution of jet axes in e + e − -annihilation follows the dependence ∝ (1 + cos 2 θ) expected for spin 1/2 objects.The quark origin of jets was proven in studies of the ratio of e + e − -annihilation cross sections to hadrons and to µ + µ − -pairs. QCD predicts that this ratio should be equal to the sum of squared charges of the objects initiating jets. In experiment, this ratio equals just its value for quarks and increases with energy at the thresholds for heavier quarks.Thus, these early findings assured us that QCD is on the right way. Later, numerous data supported this conclusion as is shown in what follows in brief. To shorten the presentation, only some of most impressive results have been chosen and no Figures are presented. More complete list with a detailed survey and Figures demonstrating comparison with experiment can be found in the books [1,2] and in recent review papers [3,4,5,6,7]. Theory.According to QCD, the primary quarks emit gluons which, in their turn, can emit e + e − -pairs and gluons. Thus the branching process of jet evolution appears. The gluons with high enough transverse momenta can create gluon jets. QCD pretends to describe jets of both quark and gluon origin. Many hadrons are created when partons become confined.

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confidence: 99%