G. Landi

The L3 silicon microvertex detector

Abstract The design and construction of the silicon strip microvertex detector (SMD) of the L3 experiment at LEP are described. We present the sensors, readout electronics, data acquisition system, mechanical assembly and support, displacement monitoring systems and radiation monitoring system of the recently installed double-sided, double-layered SMD. This detector utilizes novel and sophisticated techniques for its readout.

The Electron Spectrum From B-meson Decays

The Crystal Ball Collaboration has measured the energy spectrum of electrons from semileptonicB meson decays at thee+e− storage ring DORIS II. Branching ratios and weak mixing angles of the Kobayashi-Maskawa matrix are determined using several models for the hadronic matrix elements. We obtain the branching ratio for semileptonic.B decays to charmed states BR(B→evXc)=(11.7±0.4±1.0)%. Our result for the corresponding Kobayashi-Maskawa matrix element is |Vcb|=0.052±0.006. The model dependence of both results is included in the error. We have not observed semileptonicB decays to non-charmed mesons. Analyzing the measured electron spectrum above 2.4 GeV, where nob→c decays contribute, we find BR(B→evXu)/BR(B→evXc)<6.5% at the 90% confidence level. This corresponds to an upper limit |Vub/Vcb|<0.21.

Properties of the center of gravity as an algorithm for position measurements

The center of gravity (xg ¼ P i Eixi= P i Ei) as an algorithm for position measurements is carefully analyzed. Many mathematical consequences of discretization are extracted. The origin of the systematic error of the algorithm is shown to be connected to the absence of band limits in the Fourier Transform of the signal distributions, which, owing to the intrinsic properties of the measuring devices, must have a finite supports. However, special signal distributions exist among the finite support functions which are free from the discretized error. In the presence of crosstalk, it is proved that some crosstalk spreads are able to eliminate the discretization error for any shape. For all other cases, analytical expressions and prescriptions are given to correct the error and to efficiently simulate various experimental situations. r 2001 Elsevier Science B.V. All rights reserved.

Determination ofГ ee of the Υ(1S) and Υ(2S) resonances, and measurement ofR atW=9.39 GeV

AbstractUsing the Crystal Ball detector operating at the DORIS II storage ring we have measured the leptonic partial widthsГee of the Υ(1S) and Υ(2S) resonances. We find

The L3 Silicon Microvertex Detector: installation and results on 1993 performance

\Gamma _{ee} (\Upsilon (1S)) = 1.34 \pm 0.03 \pm 0.06keV

Properties of the center of gravity as an algorithm for position measurements: two-dimensional geometry

and

\gamma (e e

\Gamma _{ee} (\Upsilon (2S)) = 0.56 \pm 0.04 \pm 0.02keV.