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$^0$

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

A Combination of Preliminary Electroweak Measurements and Constraints on the Standard Model, 2006

This note presents a combination of published and preliminary electroweak results from the four LEP collaborations ALEPH, DELPHI, L3 and OPAL based on electron-positron collision data taken at centre-of-mass energies above the Z-pole, 130 GeV to 209 GeV (LEP-II), as prepared for the 2006 summer conferences. Averages are derived for di-fermion cross sections and forward-backward asymmetries, photon-pair, W-pair, Z-pair, single-W and single-Z cross sections, electroweak gauge boson couplings, W mass and width and W decay branching ratios. An investigation of the interference of photon and Z-boson exchange is presented, and colour reconnection and Bose-Einstein correlation analyses in W-pair production are combined. The main changes with respect to the experimental results presented in 2005 are new preliminary combinations of final LEP-II results on the mass and width of the W boson. Including the precision electroweak measurements performed at the Z pole published recently, the results are compared with precise electroweak measurements from other experiments, notably CDF and DØ at the Tevatron. Constraints on the input parameters of the Standard Model are derived from the results obtained in high-Q^2 interactions, and used to predict results in low-Q^2 experiments, such as atomic parity violation, Möller scattering, and neutrino-nucleon scattering

Precision Electroweak Measurements and Constraints on the Standard Model

This note presents constraints on Standard Model parameters using published and preliminary precision electroweak results measured at the electron-positron colliders LEP and SLC. The results are compared with precise electroweak measurements from other experiments, notably CDF and D{\O}at the Tevatron. Constraints on the input parameters of the Standard Model are derived from the results obtained in high-$Q^2$ interactions, and used to predict results in low-$Q^2$ experiments, such as atomic parity violation, M{\o}ller scattering, and neutrino-nucleon scattering