106 research outputs found
VUV absorbing vapours in n-perfluorocarbons
No full textAlbrecht E, Baum G, Bellunato T, et al. VUV absorbing vapours in n-perfluorocarbons. Nucl.Instrum.Meth. A. 2003;510(3):262-272.The optical transparency, of perfluorocarbons used as Cherenkov media is of prime importance to many Ring Imaging Cherenkov detectors. We will in this paper show that the main photon absorbers in these fluids are hydrocarbons with double or triple bonds. We will moreover discuss a process which can eliminate these pollutants and restore the intrinsic excellent optical transparency of these fluids in the VUV range. (C) 2003 Elsevier B.V. All rights reserved
The radiator gas and the gas system of COMPASS RICH-1
No full textAlbrecht E, Baum G, Bellunato T, et al. The radiator gas and the gas system of COMPASS RICH-1. In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. Nucl.Instrum.Meth. A. Vol 502. Elsevier Science BV; 2003: 266-269.The design of the COMPASS RICH-1 gas system, its operational modes, the cleaning setups for the preparation of the radiator gas and transmission measurement installations are described. The gas system in presently fully operational and satisfactory transmission of VUV light through the radiator gas has been reached. (C) 2003 Elsevier Science B.V. All rights reserved
First performances of COMPASS RICH-1
No full textAlbrecht E, Baum G, Bellunato T, et al. First performances of COMPASS RICH-1. In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. Nucl.Instrum.Meth. A. Vol 518. Elsevier Science BV; 2004: 586-589.COMPASS RICH-1, designed in 1996 for hadron identification at high momenta in the COMPASS large angle spectrometer, is based on the use of MWPCs with large size CsI photon detectors. This choice, dictated by technical and economical considerations, has imposed VUV requirements for mirror reflectance and radiator transparency. The detector is now fully operative and its preliminary performances are presented. (C) 2003 Elsevier B.V. All rights reserved
Development of Ring Imaging Cherenkov Detectors for LHCb
No full textThe work described in this thesis has been carried out in the framework of the development program of the Ring Imaging Cherenkov (RICH) detectors of the LHCb experiment. LHCb will operate at the Large Hadron Collider at CERN, and it will perform a wide range of measurements in the b-hadrons realm. The extensive study of CP violation and rare decays in the b-hadron system are the main goals of the experiment. An introduction to CP violation in hadronic interactions is given in chapter 1. The high b-b bar production cross section at the LHC energy will provide an unprecedented amount of data which will give LHCb a unique opportunity for precision tests on a large set of physics channels as well as a promising discovery potential for sources of CP violation arising from physics beyond the Standard Model. The experiment is designed in such a way to optimally match the kinematic structure of events where a pair of b quarks is produced in the collision between to 7 GeV protons. Chapter 2 is devoted to an overview of the LHCb experiment. On of the key needs of LHCb is the ability of identifying the particles emitted in the decay of b-hadrons. The wide momentum range over which positive particle identification is essential for the physics program of the experiment has led to the design of two RICH detectors, whose main features are described in chapter 3. Chapter 4 is dedicated to a set of tests performed on samples of silica aerogel, which will be one of the Cherenkov radiator of the upstream RICH detector. These tests include studies of the evolution of the optical properties of the material under irradiation as well as ageing tests of hygroscopic aerogel degradation due to exposure to humidity. The performance of silica aerogel as Cherenkov radiator has been studied in several testbeam experiments. Spherical mirrors are used in order to focus the Cherenkov photons onto the photodetectors. The mirrors are placed within the acceptance of the LHCb spectrometer and interact with particles with a probability directly proportional to their mass for a given material. Multiple scattering, bremstrahlung, pair production and showering inside the mirrors constitute a loss of information on the particles which has to be kept to the lowest possible level. Several light-weight mirror options are discussed in chapter 5, together with studies on the reflective coating choice. Before and after being reflected by the mirrors, Cherenkov photons have to traverse the gas radiator volume on their way toward the photodetectors. The transmittance of the gas must be as high as possible to maximise the number of detected photons. The last chapter is devoted to techniques of Cherenkov fluids purification and monitoring originally developed for the DELPHI RICH, and adapted on a large scale for COMPASS experiment. These previous experiences have played a substantial role in the desig n of the LHCb gas radiator systems
Measurement of sigma (pp -> bbX) at √s=7 TeV in the forward region
No full textDecays of b hadrons into final states containing a D-0 meson and a muon are used to measure the bb; production cross-section in proton-proton collisions at a centre-of-mass energy of 7 TeV at the LHC. In the pseudorapidity interval 2 < eta < 6 and integrated over all transverse momenta we find that the average cross-section to produce b-flavoured or b-flavoured hadrons is (75.3 +/- 5.4 +/- 13.0) mu b
Performance of the LHCb RICH photodetectors in a charged particle beam
No full textThe Ring Imaging Cherenkov detectors of LHCb will use pixel Hybrid Photon Detectors to measure the spatial position of Cherenkov photons. The first six pre-production photon detectors have been tested in a beam, together with prototypes of the on-detector electronics. The tests were performed at CERN using 10 GeV / c pions together with an N2 gas radiator as a source of Cherenkov light. With 1.1 m of radiator, around 10 photoelectrons were detected per track. The single-photon Cherenkov angle resolution was measured to be 1.66 ± 0.03 mrad, which is dominated by the pixelisation of the photon detector in the test-beam set-up. Both numbers agree with expectations. © 2007 Elsevier B.V. All rights reserved
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