Bottom Production in Two-Photon Collisions at LEP

Results on inclusive and exclusive bottom production in gammagamma collisions are presented. The total cross section of inclusive bottom production is investigated through its leptonic decays at LEP II energies by the experiments L3 and OPAL. The average cross section, after correction for acceptances and efficiencies, is sigma_tot = 13.3 +- 1.5 +- 2.3 pb. The next-to-leading order calculations are lower than the data by a factor three, which corresponds to a difference of more than three standard deviations. ALEPH studied the exclusive bottom production. Searching for the eta_b one candidate is found. Limits on Gamma_gammagamma(eta_b)*BR for 4 and 6 charged particles are extracted. The candidate has a mass of 9.30 +- 0.04 GeV.Comment: 4 pages, Submitted to proceedings of the Conference: DIS01, Bologn

Heavy Flavour Production in Two-Photon Collisions at LEP

New results from the experiments ALEPH, DELPHI, L3, and OPAL on heavy quark production in gammagamma collisions are presented. Inclusive charm and bottom production are investigated at LEP~2 energies. The total and differential cross sections for charm quarks are now measured by all four LEP collaborations, the total bottom by two. Charmonia are studied inclusively via the muonic decay of the J/psi and separated for the resolved and diffractive processes. New results are available for exclusive production of the eta_c meson. First searches for exclusive eta_b production are presented.Comment: Presented at the DIS2002 conference in Cracow, Poland; to be published in Acta Physica Polonica B; 7 page

Photon Structure and Heavy Flavour Production in gammagamma Collisions at LEP

New results reported at the Moriond-QCD 2003 conference from the experiments ALEPH, DELPHI, L3, and OPAL on the structure of the photon as well as heavy quark production in gammagamma collisions are presented. The hadronic structure of the photon is studied in single-tagged events; the interaction of two virtual photons is investigated in double-tagged events. Di-jet events allow, besides constraining the photon structure, investigations on the structure of jets, measurement of the di-jet as well as inclusive and differential cross sections. Inclusive charm and bottom production are investigated at LEP~2 energies. The total and differential cross sections for charm quarks are now measured by all four LEP collaborations, the total bottom by two. Charmonia are detected inclusively via the muonic decay of the J/psi and separated for the resolved and diffractive processes. Updated results are available for exclusive production of the eta_c meson. The search for exclusive eta_b production is presented.Comment: Presented at the 38th Rencontres de Moriond on QCD and High-Energy Hadronic Interactions, Les Arcs, France, 22-29 Mar. 2003; 5 page

Search for eta_b in Two-Photon Events

A search for the pseudoscalar meson eta_b was performed at LEP~II energies with an integrated luminosity of 700pb^-1. The search, done for the decay modes into 4 and 6 charged particles yielded 0 and 1 candidates, respectively. Upper limits on Gamma_gammagamma(eta_b)*BR for both modes of 57eV and 128eV were obtained with corresponding limits of 17% and 38% on branching ratios BR(eta_b) -> 4 charged particles and BR(eta_b) -> 6 charged particles at a confidence level of 95%. The candidate has a mass of 9.30 +- 0.04GeV.Comment: 4 pages, Submitted to proceedings of the Conference: PHOTON 2001, Ascon

Summary of Photon 2001

This article summarizes the experimental and theoretical results presented and discussed at the International Conference on the Structure and Interactions of the Photon, PHOTON 2001, in Ascona.Comment: 29 pages, Summary of the Photon 2001 conference held in Ascona, submitted to proceeding

Inclusive production of neutral vector mesons in hadronic Z decays

Data taken with ALEPH at LEP are presented on the inclusive production of the neutral mesons $\rho^0$(770), $\omega$(782), $\mathrm{K^{*0}}$(892), $\phi$(1020) in hadronic $\mathrm{Z^0}$ decays and compared to Monte Carlo model predictions. Bose-Einstein effects are found to be important in extracting a reliable value for the $\rho^0$ production rate; an average multiplicity of $1.45 \pm 0.22$ per event is obtained. The $\omega$ is detected via its three pion decay mode $\omega \rightarrow \pi^+\pi^-\pi^0$ and has a total rate of $1.07 \pm 0.14$ per event. $0.83 \pm 0.09$ $\mathrm{K^{*0}}$'s and $0.122 \pm 0.009$ \fn's are measured using their charged decay modes. The ratio of strange vector to pseudoscalar mesons, expressed as $\mathrm{[V/(V+P)]_s}$ is measured to be $0.51 \pm 0.06$; the strangeness suppression s/u is extracted as $0.29 \pm 0.04$

Adaptable Forward Error Correction for Multimedia Data Streams

The error handling method in traditional communication protocols is error detection and retransmission. This method is inappropriate for distributed multimedia systems for two reasons: It introduces variable delay unacceptable for isochronous streams, and it is very inefficient and difficult to use in the multicast environment typical for many multimedia applications. We propose AdFEC, an adaptable Forward Error Correction scheme based on binary polynomial algebra. It produces an adaptable amount of redundancy allowing different packet types to be protected according to their importance. The scheme was implemented in the framework of the XMovie project and proved to be very efficient

Inclusive Particle Production in Hadronic Decays of the Z Boson at LEP I

Inclusive particle production in hadronic events taken at the Z resonance with LEP~I is reviewed. With approximately 20 million Z decays, the four LEP experiments have studied the fragmentation of partons into identified particles. The high statistics allows for a detailed study of this non-perturbative QCD process. In this review the measurements of the four experiments are collected and the momentum spectra are compared to Monte Carlo models. More detailed aspects, such as relative production rates, particle content in gluon jets, particle correlation etc., are also treated

Measurement of the photon structure function at ALEPH

The photon structure function F2gamma has been measured with data taken by the ALEPH collaboration at LEP centre-of-mass energies sqrt s = 91 GeV with < Q^2 > of 9.9, 20.7 and 284 GeV^2 and sqrt s = 183 GeV with of 13.7 and 56.5 GeV^2. For the data at sqrt s = 183 GeV a two-dimensional unfolding method employing the principle of maximum entropy is used, which reduces the errors compared to one-dimensional methods.Comment: 5 pages, 5 figures, To be published in proceedings "PHOTON99

Unusual traits of cis and trans-2,3-dibromo-1,1-dimethylindane on the way from 1,1-dimethylindene to 2-bromo-, 3-bromo-, and 2,3-dibromo-1,1-dimethylindene

Do not rely on the widely accepted rule that vicinal, sp(3)-positioned protons in cyclopentene moieties should always have more positive (3)J NMR coupling constants for the cis than for the trans arrangement: Unrecognized exceptions might misguide one to wrong stereochemical assignments and thence to erroneous mechanistic conclusions. We show here that two structurally innocent-looking 2,3-dibromo-1,1-dimethylindanes violate the rule by means of their values of (3)J(cis) = 6.1 Hz and (3)J(trans) = 8.4 Hz. The stereo-selective formation of the trans diastereomer from 1,1-dimethylindene was improved with the tribromide anion (Br-3(-)) as the brominating agent in place of elemental bromine;the ensuing, regiospecific HBr elimination afforded 3-bromo-1,1-dimethylindene. The addition of elemental bromine to the latter compound, followed by thermal HBr elimination, furnished 2,3-dibromo-1,1-dimethylindene, whose Br/Li interchange reaction, precipitation, and subsequent protolysis yielded only 2-bromo-1,1-dimethylindene