Search

Pomeron was introduced as a key object which provides the non-vanishing high energy asymptotic of the total cross sections of strong interactions. The universality of this object was observed first in the studies of the elastic cross sections t-slope shrinkage. Besides the one Pomeron exchange,the unitarity generates more complicated multi-Pomeron contributions which, in particular, describe the diffractive dip structure of the differential 2 → 2 cross sections at a larger t. Somewhat unexpected universal features of Bose-Einstein correlations reported in the studies of inelastic events at CERN hadron colliders (ISR, SppS) are naturally explained within the Pomeron approach. Large Hadron Collider (LHC) opens the possibility to investigate such phenomena in more details and with a high precision.

Some basic difficulties and ambiguities on the way from the measured momentum distributions to the inferred properties of the interaction regions are reviewed and discussed.

The preliminary results on the study of Bose-Einstein Correlations between particles coming from different W bosons, in DELPHI WW events at LEP2, are presented. This manuscript is dedicated to the memory of Frans Verbeure.

Bose-Einstein correlations between like-sign charged-particle pairs in e + e − → W + W − events recorded with the OPAL detector at LEP at centre-of-mass energies between 183 GeV and 209 eV are studied. Test variables are used to investigate the presence of correlations between hadrons originating from different W bosons in W + W − → qq events. Within the statistics of the data sample no evidence for inter-WW Bose-Einstein correlations is obtained. The data are also compared with predictions'of a recent implementation of Bose-Einstein correlation effects in the Monte Carlo model PYTHIA. This presentation is based on [1].

Multiparticle effects in Bose-Einstein correlations are reviewed. It is shown that for a broad class of models they can be ignored in the low density limit, but often are significant (typically at the 10% level) for realistic denisties., Comment: 8 pages, Latex, no figures, Conference QCD'04 Montpellier, July 2004

The status of the analyses of Bose-Einstein Correlations (BEC) at LEP is given. In particular the latest results of a two-dimensional analysis of BEC in hadronic Z decays and the results of a new analysis of inter-W BEC by ALEPH are presented.

Bose-Einstein correlations in W-pair production at LEP are investigated in a data sample of 629 pb−1 collected by the L3 detector at √s = 189–209 GeV. Bose-Einstein correlations between pions within a W decay are observed and found to be in good agreement with those in light-quark Z decay. No evidence is found for Bose-Einstein correlations between hadrons coming from different W's in the same event.

Latest measurements of Bose-Einstein correlations at LEp and HERA colliders are reviewed.

A review of Bose-Einstein correlations is presented here using data collected at LEP. Bose-Einstein correlations have been studied in hadronic Z decays produced in e+e− interactions at √s ~ 91 GeV. They have been observed in pairs of identical pions, charged and neutral, showing a smaller size for the neutral source. Also a multidimensional analysis has been performed that shows an elongation of the source along the direction of the motion of the original quark. At higher centre of mass energies, (√s ~ 200 GeV), it was possible to study the Bose-Einstein effect in W-pair production. In particular, Bose-Einstein correlations are investigated between particles coming from different W's as they may influcence the W mass measurement in the four-jet channel.

A report is given on a study of Bose-Einstein correlations in W-pair production at LEP2. In particular, Bose-Einstein correlations are investigated in W+W− overlap and the possible existence of these correlations between particles coming from different W's, which may influence the W mass measurements in the four-jet channel e+e− → W+W− → q1 q 2q3 q 4. Results obtained by the L3 and Opal detectors are given. No evidence for such an inter-W Bose-Einstein correlation is found by L3 and the results of Opal are inconclusive due to lack of statistics.

A report is given on a study of Bose-Einstein correlations in W-pair production at √ s = 189 GeV with the L3 detector at LEP. In particular, Bose-Einstein correlations are investigated in W + W − overlap and the possible existence of these correlations between particles coming from different W's, which may influence the W mass measurements in the four-jet channel e + e − → W + W − → q 1 q 2 q 3 q 4 . No evidence for such an inter-W Bose-Einstein correlation is found. These results are preliminary.

The effect of Bose-Einstein correlations on multiplicity distributions of identical pions is discussed. It is found that these correlations affect significantly the observed multiplicity distributions, but Einstein's condensation is unlikely to be achieved, unless "cold spots", i.e. regions, where groups of pions with very small relative momenta are produced, occur in high energy heavy-ion collisions., Comment: 8 pages Latex, no figures, Conference QCD99, Montpellier July 1999

In this talk I will present and discuss the charged-particle multiplicity distributions, the forward-backward correlations, the intermittency, the average transverse momenta, and the Bose-Einstein correlations measured in e + e − collisions at LEP.

Bose-Einstein correlations are studied in the framework of a class of independent particle production models. This generalizes the studies for a variety of models proposed previously. It is shown that the Bose-Einstein correlations lead for this class of models to Einstein's condensation at sufficiently high density. They also enhance unusual charge distributions and may explain the centauro and anticentauro events reported by cosmic ray physicists. For typical models the correlations cause a shrinking of the momentum distribution of the produced identical particles and an apparent shrinking of the production region., Comment: 6 pages Latex, no figures. Report at the Conference QCD98, Montpellier, July (1998)