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0370-2693r98r$ -see front matter q 1998 Elsevier Science B.V. All rights reserved.Ž . PII: S 0 3 7 0 -2 6 9 3 9 8 0 0 7 3 6 -9 ( ) M. Acciarri et al.r Physics Letters B 434 1998 169- AbstractWe analyse e q e y ™ ttg events using 100 pb y1 of data collected by the L3 experiment during the 1991-1995 LEP runs at the Z pole. From the energy of the photons and their isolation from the tau decay products, we determine the anomalous magnetic and electric dipole moments of the tau to be, respectively: a s 0.004 " 0.027 " 0.023; t d s 0.0 " 1.5 " 1.3 = 10 y16 e P cm. Ž .t This is a direct measurement of these t form factors at q 2 s 0. q 1998 Elsevier Science B.V. All rights reserved.

A search for heavy neutrinos that are isosinglets under the standard SU(2)L gauge group is made at center-of-mass energies 130 -'s -189 GeV with the L3 detector at LEP. Such heavy neutrinos are expected in many extensions of the Standard Model. The search is performed for the first generation heavy singlet neutrino, Ne, through the decay modeNe ™ e + W. We set upper limits on the mixing parameter between the heavy and light neutrino for the heavy neutrino mass range from 80 GeV to 185 GeV.

We present a measurement of the average b-hadron lifetime b at the e

New measurements at a centre-of-mass energy √ s 183 GeV of the hadronic photon structure function F γ 2 (x) in the Q 2 interval, 9 GeV 2 ≤ Q 2 ≤ 30 GeV 2 , are presented. The data, collected in 1997 with the L3 detector, correspond to an integrated luminosity of 51.9 pb −1. Combining with the data taken at a centreof-mass energy of 91 GeV, the evolution of F γ 2 with Q 2 is measured in the Q 2 range from 1.2 GeV 2 to 30 GeV 2. F γ 2 shows a linear growth with ln Q 2 ; the value of the slope α −1 dF γ 2 (Q 2)/d ln Q 2 is measured in two x bins from 0.01 to 0.2 and is somewhat higher than predicted.

The three different helicity states of W bosons produced in the reaction e+e-→lvqq at LEP are studied using leptonic and hadronic W decays. Data at centre-of-mass energies √s=183–209 GeV are used to measure the polarisation of W bosons, and its dependence on the W boson production angle. The fraction of longitudinally polarised W bosons is measured to be 0.218±0.027±0.016 where the first uncertainty is statistical and the second systematic, in agreement with the Standard Model expectation

A search for the lightest neutral scalar and neutral pseudoscalar Higgs bosons in the Minimal Supersymmetric Standard Model is performed on data collected at LEP by the L3 detector at center-of-mass energies 130 GeV ≤ p s ≤ 183 GeV. No significant excess of events is observed. Limits on the masses of the lightest neutral and pseudoscalar Higgs bosons are given as a function of tan β. Lower mass limits at the 95% confidence level are set at m h > 70.7 GeV and m A > 71.0 GeV.

Most of the work related to water production in oil wells found in literature deals with the problem of determining the critical flow rate for water coning, but very few has been done to determine the water production above the critical rate. Moreover, the available correlations use to differ considerably.The aim of the present study was to determine the performance of water production in a single well for a range of operational conditions and petrophysical parameters characterizing a petroleum reservoir. A well simulation model in radial geometry was constructed, considering undersaturated oil and including a water contact. The model was simple enough to allow for the simulation of the thousands of cases required to perform the sensitivity analysis at reasonably low computer cost. Variation intervals were taken for selected parameters; for the rest of them reasonable average values were considered. This technique applied to a numerical simulation model constitutes a powerful tool for generating enough statistical data to analyse the behaviour of water production.A database consisting of almost 20,000 cases was built, comprising both cases in which the production is carried out with a flow rate smaller than the critical one, and cases in which the cone instability is reached and the flow rate is higher than the critical one.Existing correlations for breakthrough time and water production were checked for validity against the database. It was found that, although in some cases they provide a reasonable approximation, there are many cases in which this is not true, despite the relative simplicity of the cases Based on this evidence, it is clear that better, more general correlations are needed. A correlation for breakthrough time was developed, for a wider range of validity than existing ones with respect to the reservoir parameters. As future work we plan to analyse the large amount of useful information generated and stored in our database to seek for functional relationships between water production and operational and petrophysical parameters.