S. Menary

The design, construction and performance of the ALEPH silicon vertex detector

Abstract The ALEPH silicon vertex detector is the first detector operating in a colliding beam environment that uses silicon strip detectors which provide readout on both sides and hence a three-dimensional point measurement for the trajectory of charged particles. The detector system was commissioned successfully at the e+e− collider LEP at the research centre CERN, Switzerland, during the year 1991 while taking data at the Z0 resonance. The achieved spatial resolution of the complete 73 728 channel device (intrinsic plus alignment) is 12 μm in the r-f view and 12 μm in the z view. The design and construction of the entire detector system are discussed in detail and the experience gained in running the detector will be described with special emphasis on the uses of this novel tracking device for the physics of short-lived heavy particles produced in the decays of the Z0 resonance.

Recent results and running experience of the new ALEPH Vertex Detector

A description of the new ALEPH Vertex Detectors (VEDET 91), including the new mechanical structure and the improved data acquisition system, is given. The apparatus consists of two complete layers of silicon detectors with double-sided readout which provide full x,y,z information on the impact points of charge particles. The authors present results on signal-to-noise ratio for minimum ionizing particles and efficiency in hit/track matching. Results on position, impact parameter, and momentum resolution are also shown as measured using high-momentum muons. Preliminary results on single hit and impact parameter resolution show that the detectors and VLSI read-out electronics work as expected, and the performance compares well with previous test beam results and Monte Carlo simulations. Preliminary results on precision vertex reconstruction show a significant improvement in the data analysis which will be fully exploited in studying tau , b and c physics when all statistics are available.<<ETX>>

Operational experience with a large detector system using silicon strip detectors with double sided readout

Abstract A large system of silicon strip detectors with double sided readout has been successfully commissioned over the course of the last year at the e + e − collider LEP. The readout of this 73 728 channel system is performed with custom designed VLSI charge sensitive amplifier chips (CAMEX64A). An overall point resolution of 12 μm on both sides has been acheived for the complete system. The most important difficulties during the run were beam losses into the detector, and a chemical agent deposited onto the electronics; however, the damage from these sources was understood and brought under control. This and other results of the 1991 data-taking run are described with special emphasis on the operational experience.

The Aleph silicon vertex detector

Abstract The Aleph silicon vertex detector at the LEP e+e− collider at CERN is described. A detailed information on the various components of the detector is given. Preliminary results obtained during 1990 LEP running are presented.

Study of the B0 semileptonic decay spectrum at the Y(4S) resonance

We have made a first measurement of the lepton momentum spectrum in a sample of events enriched in neutral Bs through a partial reconstruction of B{sup 0} {yields} D*{sup -}{ell}{sup +}{nu}. This spectrum, measured with 2.38 fb{sup -1} of data collected at the {Upsilon}(4S) resonance by the CLEO II detector, is compared directly to the inclusive lepton spectrum from all {Upsilon}(4S) events in the same data set. These two spectra are consistent with having the same shape above 1.5 GeV/c. From the two spectra and two other CLEO measurements, we obtain the B{sup 0} and B{sup +} semileptonic branching fractions, b{sub 0} and b{sub +}, their ratio, and the production ratio f{sub +-}/f{sub 00} of B{sup +} and B{sup 0} pairs at the {Upsilon}(4S). We report b{sub +}/b{sub 0} = 0.950{sub -0.080}{sup +0.117} {+-} 0.091, b{sub 0} = (10.78 {+-} 0.60 {+-} 0.69)%, and b{sub +} = (10.25 {+-} 0.57 {+-} 0.65)%. b{sub +}/b{sub 0} is equivalent to the ratio of charged to neutral B lifetimes, {tau}{sub +}/{tau}{sub 0}.