[en] The Lhc experiment intends to perform highly accurate measurements on C P-violating processes and rare decays of B-mesons at the Large Hadron Collider. The ratio between the expected p-p inelastic cross-section (about 100 mb) and the b-b cross-section (0.5 mb) demands for a very robust and efficient trigger system. In this paper the two trigger levels (Level-0 and High Level Trigger) foreseen for the experiment are described and their main performance analyzed. The expected annual yields of some of the most interesting B-decay channels are also summarized.

[en] The dual-readout approach, which allows an event-by-event measurement of the electromagnetic shower fraction, was originally demonstrated with the DREAM sampling calorimeter. This approach can be extended to homogeneous detectors like crystals if Cherenkov and scintillation light can be separated. In this paper we present several methods we developed for distinguishing the two components in PWO and BGO based calorimeters and the results obtained.

[en] We report the results of a systematic study of the time performance of triple-GEM detectors operated with several gas mixtures which are new for this kind of detectors. We show that a considerable improvement, with respect to the traditional gas mixture Ar/CO₂ (70/30), is obtained with the fast and high yield based CF₄ and iso-C₄H₁₀ gas mixtures; time resolutions better than 5 ns. Discharge studies have been performed with high intensity π/proton beams at the Paul Sherrer Institute (PSI). The results show that the operation of the detector is very stable, if a small fraction of iso-C₄H₁₀ or a large amount of CF₄, is use

[en] The LHCb Muon System is composed of five detection stations maninly equipped with a total of 1368 Multi-Wire Proportional Chambers. In order to allow a fast evaluation of the transverse momentum of the muon, the detectors have to provide a fast response and a high efficiency. We present a novel precise study of the performance of different chambers, completely equipped with the final Front-End Electronics, measured with cosmic rays. Measurements of the time and space resolution have been carried out as a function of the gas gain and discriminator threshold along with detailed studies of the time and space structure of the cross-talk hits. The studies perfomed are usefuls to get a better knowledge of the behavior of the chambers and to optimize the working conditions on the apparatus during the LHCb data taking

[en] The performance of different types of multi-wire proportional chambers belonging to the LHCb Muon System was tested in laboratory with cosmic rays. The detection efficiency, the time and spatial resolution were measured and the high-voltage working region of these chambers was determined. These tests provide information which is complementary to those obtained in the final LHCb apparatus.

[en] We report the results of a study of triple-GEM detectors for high rate charged particle triggering. This study was performed in the framework of an R and D activity on detectors for the Level-0 LHCb muon trigger and, in particular, for the inner regions (R1 and R2) of the first station (Ml), where particle rates up to 460 kHz/cmz are expected. A crucial requirement in this application is an efficiency higher than 99% per station (two detectors logically OR-ed) in a 25 ns time window. Results of the time performance are compared with the discharge probability per incident particle as results from a study performed with a high intensity hadron beam. We show here the considerable improvement obtained with the addition of CF₄ and/or iso-C₄H₁₀ to the widely used Ar/CO₂ mixture. Which allows to satisfy the experiment requirements

[en] We report the results of a systematic study of the performance of 10x10 cm² triple-GEM detectors operated with several gas mixtures. In a previous paper, we pointed out that adding CF₄ to the standard Ar/CO₂ gas mixture allows to improve the time resolution of the detector from ∼10 ns down to ∼6 ns (r.m.s.). In this paper, we discuss the results obtained with CF₄ and iso-C₄H₁₀-based gas mixtures, during a beam test at the πM1 beam facility of the Paul Scherrer Institute (PSI). Preliminary results concerning the discharge probability of triple-GEM detector, when exposed to both high intensity pion/proton beam and α-particles from a radioactive source are presented. Gain measurements and aging tests, using a high intensity 5.9 keV X-ray tube, are eventually discussed

[en] The Gas Electron Multiplier (GEM) (Nucl. Instr. and Meth. A 386 (1991) 531) based detectors have been widely developed in last years and proposed for many different applications. In order to reach a better understanding of such kind of detector the computer simulation is an important and powerful tool. In this paper the method for a GEM-based detector simulation and the results obtained are discussed and compared with experimental data. A good agreement has been found making this method a promising tool for detector study and optimization

[en] In this paper, results of a time performance study of triple gas electron multiplier (GEM) detectors are discussed. This study was driven by an R and D activity on detectors for the Level 0 LHCb muon trigger. However, the results presented in this paper are of more general interest, i.e. for experiments with high rate charged particle triggering. Little interest was given so far to time performance of GEM detectors. Only one group measured double GEM detector time resolution with the Ar/CO₂ (70/30) gas mixture. Our study aimed at triple GEM detector optimisation for good time performance through a detailed investigation of the role played by detector geometry, electric fields and gas mixture. The results reported here, in particular when using the gas mixture Ar/CO₂/CF₄ (60/20/20), considerably improve the time performance discussed in the above-mentioned paper and make the triple GEM detector a promising option for high rate charged particle triggering

[en] Triple-GEM chambers, so far used in the inner region of the first muon station at LHCb, are the ideal candidates to replace the MWPCs in the regions where, after the upgrade in 2018, the particle rate will be as high as 2MHz/cm"2. In this work, the results of a study on the GEM efficiency and time performances are shown.