G. Sguazzoni

THE NEW ALEPH SILICON VERTEX DETECTOR

The ALEPH collaboration, in view of the importance of effective vertex detection for the Higgs boson search at LEP 2, decided to upgrade the previous vertex detector. Main changes were an increased length (+/- 20 cm), a higher granularity for r phi view (50 mu m), a new preamplifier (MX7 rad hard chip), a polymide (upilex) fan-out on z side to carry the signals from the strips to the front-end electronics outside the fiducial region reducing consequently the passive material in the central region by a factor of two. The detector, the running experience and its performance will be described

Construction and performance of the new ALEPH Vertex Detector

A new Silicon Vertex Detector was developed for the ALEPH experiment and first installed for the high energy run at 130 GeV at the end of 1995. The detector has an active length of 40 cm and consists of two concentric layers of silicon wafers with double-sided readout. It extends the angular coverage, has only half the passive material as the former detector in the tracking volume and is radiation hard to cope with the higher level of radiation background expected for the LEP2 phase. The construction and the performance of the detector is described.

SUSY Particles Searches at LEP and Interpretations within the MSSM

Abstract Searches for R-parity conserving supersymmetric particles have been performed in e + e − data collected by LEP detectors, at centre-of-mass energies up to 209 GeV, corresponding to an integrated luminosity of ∼3.1 fb −1 . The results and their interpretation in the context of MSSM frameworks are briefly reviewed.

The CMS Si-strip tracker

The Compact Muon Solenoid (CMS) experiment at LHC features the largest Silicon Strip Tracker (SST) ever build. This device is immersed in a 4T magnetic field and, in conjunction with a Pixel system, it allows the momentum of the charged particles to be measured and the heavy-flavour final states to be tagged despite the hostile radiation environment. The impact of operating conditions and physics requirements on the SST layout and design choices is discussed and the expected performances are reviewed. The SST collaboration is now facing the production of the ~15000 modules and their assembly into the SST substructures. A status is given.

Monitoring the Stability of the ALEPH Vertex Detector

Abstract The ALEPH Silicon Vertex Detector features an optical fibre laser system to monitor its mechanical stability. The operating principle and the general performance of the laser system are described. The experience obtained during 1997 and 1998 operations confirms the important role that such a system can have with respect to the detector alignment requirements. In particular, the laser system has been used to monitor short-term temperature-related effects and long-term movements. These results and a description of the laser-based alignment correction applied to the 1998 data are presented.

The construction of the CMS Silicon Strip Tracker

The CMS Silicon strip tracker is a very large scale tracker entirely based on Silicon strip detector technology. It is build up of ∼ 15 k Silicon strip modules for a total of ∼ 9 M analogue readout channels with an overall active silicon area of ∼ 200 m 2 , to be operated at − 10 ° C and able to survive for 10 years to the LHC radiation environment. The integration of modules, electronics, mechanics and services has been completed within the last two years; large standalone sub-structures (shells, disks, rods and petals depending on the tracker subdetector) have been first integrated and verified; then they have been brought together into the final configuration. The CMS silicon tracker design and its construction is reviewed with particular emphasis on the procedures and quality checks deployed to successfully assembly several modules and all ancillary components into these large sub-structures. An overview of the results and the lesson learned from the tracker integration are given, also in terms of failure and damage rates.

Performance of the Aleph upgraded silicon vertex detector

The ALEPH Vertex Detector (VDET) has been upgraded for the second phase of LEP running. The new version still uses double sided silicon strip detectors, fabricated with the same technology as the previous one, but the upgraded one is twice as long and has about half passive material in the tracking volume. Furthermore the readout electronics is now radiation hard (MX7-RH chips). An almost complete version of the upgraded VDET was installed in ALEPH during a three week LEP technical stop and took data in November 1995 during the LEP run at 130 GeV. The new detector worked well showing high signal over noise ratio and good efficiency. The point resolution measured during this run, using high momentum muons, 13 μm in the τ - φ view and 21 μm in the τ - z view, is dominated by the alignment precision, due to the low statistics available for this short LEP run. This result is however acceptable, since for lower momentum charged particle, the multiple scattering gives a significant contribution to the final impact parameter resolution. A better resolution has been achieved in the next run, when an initial period at the Z peak has been foreseen to calibrate and align the whole detector.