R. Antunes Nobrega

Performance of the LHCb muon system

The performance of the LHCb Muon system and its stability across the full 2010 data taking with LHC running at root s = 7 TeV energy is studied. The optimization of the detector setting and the time calibration performed with the first collisions delivered by LHC is described. Particle rates, measured for the wide range of luminosities and beam operation conditions experienced during the run, are compared with the values expected from simulation. The space and time alignment of the detectors, chamber efficiency, time resolution and cluster size are evaluated. The detector performance is found to be as expected from specifications or better. Notably the overall efficiency is well above the design requirements.

Performance of the LHCb muon system with cosmic rays

The LHCb Muon system performance is presented using cosmic ray events collected in 2009. These events allowed to test and optimize the detector configuration before the LHC start. The space and time alignment and the measurement of chamber efficiency, time resolution and cluster size are described in detail. The results are in agreement with the expected detector performance.

A new method based on noise counting to monitor the frontend electronics of the LHCb muon detector

A new method has been developed to check the correct behaviour of the frontend electronics of the LHCb muon detector. This method is based on the measurement of the electronic noise rate at different thresholds of the front-end discriminator. The method was used to choose the optimal discriminator thresholds. A procedure based on this method was implemented in the detector control system and allowed the detection of a small percentage of front-end channels which had deteriorated. A Monte Carlo simulation has been performed to check the validity of the method.

Performance of the MWPC of the first station of the LHCb Muon System

The LHCb Muon System is composed of five detection stations (M1-M5) equipped with a total of 1368 Multi-Wire Proportional Chambers (MWPC) and 12 triple-GEM based detectors. The first station (M1) is placed upstream of experiment calorimeters and thus is equipped with very “light” MWPC made by only two gas-gaps (instead of four) and with triple-GEM based detectors. The chambers have to provide a high detection efficiency, a fast response and a good space resolution. For the first time the performance of different M1 MWPC completely equipped with the final Front-End Electronics, have been tested with cosmic rays. The detection efficiency, the time resolution and the hit multiplicity were measured. Chambers with anode-wire-readout and with cathode-pad-readout were tested and the results are compared. The results obtained will be used to individuate the optimized working conditions of the apparatus and to make a more realistic detector description in the LHCb Monte Carlo simulation.

Performance of the quadri-gap LHCb Muon Chambers studied with cosmic rays

The LHCb muon system is composed of five detection stations (M1-M5) mainly equipped with a total of 1368 multi-wire proportional chambers (MWPC). In order to allow a fast evaluation of the transverse momentum of muons, the MWPC have to provide a high detection efficiency, a fast response and a good space resolution. We present the results of a detailed study of the performance of different chambers, completely equipped with the final front-end electronics, measured with cosmic rays. A stand able to house 6 MWPCs and to acquire 600 TDC channels a time was used in order to measure the detection efficiency, the time resolution and the hit multiplicity as a function of the gas gain. For the first time, both the chambers with anode-wire-readout and chambers with cathode-pad-readout were tested and the results are compared. The large amount of acquired data results to be very useful to get a better knowledge of the behaviour of the chambers allowing to individuate the optimised working conditions of the apparatus and to make a realistic detector description in the LHCb Monte Carlo simulation.