Can quantized fragmentation replace colour reconnection models ?

A brief overview of properties of the model of quantized fragmentation of a helical QCD string is followed by the discussion of colour reconnection models and of the ways to reproduce the evolution of the average transverse momentum in hadronic events, as function of charged particle multiplicity. Reference to recent experimental data is included.Comment: 5 pages, 4 figures. Proceedings of ISMD202

About the helix structure of the Lund string

The helix structure of the Lund string, first derived from studies devoted to the emission of soft gluons at the end of the parton cascade, may be at the origin of a part of the 'correlations' observed in multidimensional analyses of the Bose-Einstein effect. It is found that a helix structure of the string corresponding to an emission of soft gluons from a regularly spinning source is supported by the data, more precisely by the inclusive single-particle spectra measured in the hadronic decay of Z$^0$

Interconnection Effects in Multiparticle Production from WW Events at LEP

Interactions between the products of the hadronic decays of different Ws in WW pair events can occur at several stages: from the colour rearrangement between the quarks coming from the primary branching, to the gluon exchange during the parton cascade, to the mixing of identical pions due to Bose-Einstein correlations. Besides the intrinsic interest of their study related to the understanding of the multiparticle production mechanisms, these phenomena can affect the ultimate accuracy in the W mass measurement by LEP 2. The status of the experimental analysis on interconnection effects between W pairs hadronically decaying is reviewed in this paper.Comment: 10 pages, 7 figures. To be published in Proc. XXVII International Symposium on Multiparticle Dynamics; Laboratori Nazionali di Frascati (Roma), September 199

Numerical modelling of Bose-Einstein correlations

We propose extension of the algorithm for numerical modelling of Bose-Einstein correlations (BEC), which was presented some time ago in the literature. It is formulated on quantum statistical level for a single event and uses the fact that identical particles subjected to Bose statistics do bunch themselves, in a maximal possible way, in the same cells in phase-space. The bunching effect is in our case obtained in novel way allowing for broad applications and fast numerical calculations. First comparison with $e^+e^-$ annihilations data performed by using simple cascade hadronization model is very encouraging.Comment: LaTeX file and 5 eps file with figures, 9 pages altogethe

Quarkonium production in deep-inelastic scattering

We discuss the inclusive production of J/psi mesons in deep-inelastic scattering (DIS) via the electromagnetic, weak neutral, and charged currents within the factorization formalism of nonrelativistic quantum chromodynamics. Theoretical predictions are confronted with experimental data of e p and nu N DIS taken by the H1 Collaboration at DESY HERA and the CHORUS Collaboration at CERN, respectively.Comment: 6 pages (Latex), 6 figures (Postscript); to appear in the Proceedings of the 6th International Symposium on Radiative Corrections: Application of Quantum Field Theory to Phenomenology (RADCOR 2002), Kloster Banz, Germany, September 8-13, 200

J/psi Inclusive Production in nu N Neutral-Current Deep-Inelastic Scattering

We calculate the cross section of J/psi inclusive production in neutrino-nucleon deep-inelastic scattering via the weak neutral current within the factorization formalism of nonrelativistic quantum chromodynamics. Besides J/psi single production via the Z-gluon fusion mechanism, we also consider J/psi plus hadron-jet associated production. We take into account both direct production and feed-down from directly-produced heavier charmonia. We present theoretical predictions for the J/psi transverse-momentum and rapidity distributions, which can be measured in the CHORUS and NOMAD experiments at CERN, including conservative error estimates. In order to interpret a recent CHORUS measurement of the total cross section, we also estimate the contribution due to J/psi prompt production via diffractive processes using the vector-meson dominance model.Comment: 34 pages (Latex), 5 figures (Postscript); significantly extended to include feed-down and diffractive contributions and nuclear corrections; accepted for publication in Nucl. Phys.

Evidence for Colour-Octet Mechanism from CERN LEP2 gamma gamma -> J/psi + X Data

We present theoretical predictions for the transverse-momentum distribution of J/psi mesons promptly produced in gamma gamma collisions within the factorization formalism of nonrelativistic quantum chromodynamics, including the contributions from both direct and resolved photons, and we perform a conservative error analysis. The fraction of J/psi mesons from decays of bottom-flavoured hadrons is estimated to be negligibly small. New data taken by the DELPHI Collaboration at LEP2 nicely confirm these predictions, while they disfavour those obtained within the traditional colour-singlet model.Comment: 11 pages (Latex), 3 figures (Postscript); updated experimental data included, references added, accepted for publication in Phys. Rev. Let