QCD Interconnection Studies at Linear Colliders

Heavy objects like the W, Z and t are short-lived compared with typical hadronization times. When pairs of such particles are produced, the subsequent hadronic decay systems may therefore become interconnected. We study such potential effects at Linear Collider energies.Comment: 1+7 pages, 6 figure

QCD Interconnection Effects

Heavy objects like the W, Z and t are short-lived compared with typical hadronization times. When pairs of such particles are produced, the subsequent hadronic decay systems may therefore become interconnected. We study such potential effects at Linear Collider energies.Comment: 1+4 pages, no figures, to appear in the Proceedings of the International Workshop on Linear Colliders, Sitges (Barcelona), Spain, April 28 - May 5, 199

QED Interconnection Effects on W Momentum Distributions at LEP 2

The process \ee \to \W^+\W^- \to \f_1 \fbar_2 \, \f_3 \fbar_4 contains charges in the initial, intermediate and final stages. This gives a rich selection of possible QED interconnection effects. Coulomb interaction is the simplest of these, and can thus be used to explore consequences. We study a number of experimental observables, with emphasis on those related to the W momentum distribution. Second-order Coulomb effects are shown to be practically negligible. The limited LEP~2 statistics will not allow detailed tests, so any theory uncertainty will be reflected in the systematic error on the W mass. Currently the uncertainty from this source may be as high as 20~MeV.Comment: 1+27 pages, including 23 eps figures, use uudecode and gunzip to restore original file, run LaTeX2epsilon with epsfig package, figures are included in filecontents environments; alternatively ready-made postscript file is available at http://thep.lu.se/tf2/staff/torbjorn/Welcome.htm

Analytical QCD and multiparticle production

We review the perturbative approach to multiparticle production in hard collision processes. It is investigated to what extent parton level analytical calculations at low momentum cut-off can reproduce experimental data on the hadronic final state. Systematic results are available for various observables with the next-to-leading logarithmic accuracy (the so-called modified leading logarithmic approximation - MLLA). We introduce the analytical formalism and then discuss recent applications concerning multiplicities, inclusive spectra, correlations and angular flows in multi-jet events. In various cases the perturbative picture is surprisingly successful, even for very soft particle production.Comment: 97 pages, LaTeX, 22 figures, uses sprocl.sty (included

Perturbative universality in QCD jet physics

I survey some recent advances in the applications of the analytical perturbative approach to the description of particle distributions in multi-jet processes. New tests of the perturbatively based picture in the (semi) soft region are discussed.Comment: LaTeX, 15 pages, talk at the XXVII International Symposium on Multiparticle Dynamics, Frascati (Rome), Italy, 8-12 September 199

QED-Induced Rapidity-Gap Events at the Z Peak

We study rapidity-gap events in $e^+e^-$ annihilation at the Z boson peak initiated by the emission of a virtual photon. This mechanism is suppressed by the QED coupling constant, but it is enhanced due to a large propagator term from the virtual photon. For typical kinematics, we find a smaller event rate than analogous QCD type gap events. In the small jet-pair invariant mass limit, the QED type events follow a $1+\cos^2\theta$ distribution in the jet-pair scattering angle, instead of the $\sin^2\theta$ distribution of the QCD case.Comment: 13 pages, plain TeX (needs the PHYZZX macros), 4 figures in PostScript. SLAC-PUB-6116, DOE/ER/40762-009, U of Md. PP \#93-19