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Comment: 15 pages, 1 postscript figures, contributed to Proceedings of the ICHEP2000 Conference
This document is the final report of the LHC Computing Grid (LCG) Project's Requirements and Technical Assessment Group (RTAG 12) on Collaborative Tools. It presents a summary of the requirements of the LHC collaborations for Collaborative Tools, assesses the current status of those tools in common use, discusses likely relevant future development, and provides recommendations for action by the LCG, the collaborations, and CERN for the immediate and long-term future. The requirements and assessments were assembled from formal and informal interactions between members of the RTAG, representatives of the LHC collaborations, CERN IT, and experts in the field of Collaborative Tools.
A study of neutral-current four-fermion processes is performed, using data collected by the L3 detector at LEP during high-energy runs at centre-of-mass energies 130 - 136, 161 and 170 - 172 GeV, with integrated luminosities of 4.9, 10.7 and 10.1 pb$^{-1}$, respectively. The total cross sections for the final states $ \ell\ell \ell^\prime \ell^\prime $ and $\rm \ell\ell qq $ ($\ell$,~$\ell^\prime $ = e, $\mu$ or $\tau$) are measured and found to be in agreement with the Standard Model prediction.
We present a study of the inclusive $\omega$ and $\eta^{\prime}$ production based on 3.1 million hadronic Z decays recorded with the L3 detector at LEP during 1991--1994. The production rates per hadronic Z decay have been measured to be $1.17 \pm 0.17 $ $\omega$ mesons and $0.25 \pm 0.04 $ $\eta^{\prime}$ mesons. The production rates and the differential cross sections have been compared with predictions of the JETSET and the HERWIG Monte Carlo models. We have observed that the differential cross sections can be described by an analytical quantum chromodynamics calculation. \end{document}
We present a measurement of the average b-hadron lifetime ${\rm \tau_b}$ at the $\mathrm{e^+e^-} \, $ collider LEP. Using hadronic Z decays collected in the period from 1991 to 1994, two independent analyses have been performed. In the first one, the b-decay position is reconstructed as a secondary vertex of hadronic b-decay particles. The second analysis is an updated measurement of ${\rm \tau_b}$ using the impact parameter of leptons with high momentum and high transverse momentum. The combined result is \begin{center} ${\rm \tau_b= [ 1549 \pm 9 \, (stat) \, \pm 15 \, (syst) ] \; fs \,}$ . \end{center} In addition, we measure the average charged b-decay multiplicity ${\rm \langle n_{\rm b}} \rangle$ and the normalized average b-energy ${\rm \langle x_E \rangle_{\rm b}}$ at LEP to be \begin{center} ${\rm \langle n_{\rm b} \rangle = 4....
The measurements of hadron and lepton--pair production cross sections and lepton--pair forward--backward asymmetries performed with the L3 detector at centre--of--mass energies between 130 GeV and 172 GeV are used to search for new physics phenomena. New physics effects involving four fermion vertices -- contact interactions -- are looked for in all channels. For hadron production the exchange of virtual leptoquarks and scalar quarks is studied. No evidence for deviations from the Standard Model expectations is found. Lower limits on the scale $\Lambda$ of contact interactions in the range 1.2 -- 7.1 TeV are obtained at the 95\% confidence level for various models. Upper limits on the coupling strengths of leptoquarks and scalar quarks are derived.
The reaction $\mathrm{e}^{+} \mathrm{e}^{-} \rightarrow \mathrm{e}^{+} \mathrm{e}^{-} \gamma ^{*} \gamma ^{*} \rightarrow \mathrm{e}^{+} \mathrm{e}^{-} $ {\sl hadrons} is analysed using data collected by the L3 detector during the LEP runs at $\sqrt {s}$ = 130-140 GeV and $\sqrt {s}$ = 161 GeV. The cross sections $\sigma(\mathrm{e}^{+} \mathrm{e}^{-} \rightarrow \mathrm{e}^{+} \mathrm{e}^{-} $ {\sl hadrons}) and $\sigma (\gamma\gamma \rightarrow $ {\sl hadrons}) are measured in the interval 5 $\leq W_{\gamma\gamma} \leq$ 75 GeV. The energy dependence of the $\sigma (\gamma\gamma \rightarrow $ {\sl hadrons}) cross section is consistent with the universal Regge behaviour of total hadronic cross sections. %\end{abstract}
We report on the observation of single W boson production in a data sample collected by the L3 detector at LEP2. The signal consists of large missing energy final states with a single energetic lepton or two hadronic jets. The cross-section is measured to be $0.61^{+0.43}_{-0.33} \pm 0.05 \; \rm{pb}$ at the centre of mass energy $\sqrt{s}=172 \GeV{}$, consistent with the Standard Model expectation. From this measurement the following limits on the anomalous $\gamma$WW gauge couplings are derived at 95\% CL: $\rm -3.6 \Delta \kappa_\gamma 1.5$ and $\rm -3.6 \lambda_\gamma 3.6$.
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