The Vertex Locator (VELO) of the LHCb experiment consists of two halves each equipped with 23 silicon modules along the beam direction. The detector is mounted in a setup similar to Roman pots. The ...VELO will offer a powerful tool for primary and secondary vertex reconstruction. In order to achieve this, the detector went through a complete and thorough commissioning phase. This process spans a range of activities: individual module characterization in testbeams, detector integration, system tests and offline alignment procedures. After this extensive commissioning period the LHCb experiment entered a new exciting phase during the year 2008. The experiment saw the first beam! Moreover with data taken in the VELO detector the first LHC induced tracks could be reconstructed.
The Ring Imaging Cherenkov detectors of the LHCb experiment will offer a powerful tool for particle identification in the momentum range from 1 to
∼
100
GeV
/
c
. In order to achieve this, a thorough ...commissioning phase has now started spanning photon detector integration to offline alignment procedures.
This paper will focus on alignment, detector monitoring and control issues, as well as data quality tests. The operation of the photon detectors, readout chain and data acquisition in the experimental environment will be covered.
Performance of the light monitoring system for CMS-ECAL Van Lysebetten, A.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2004, Letnik:
518, Številka:
1
Journal Article
Recenzirano
The electromagnetic calorimeter (ECAL) of CMS is constituted of nearly 80
000 PbWO
4 crystals. Small variations in the light transmission of these crystals are expected in the harsh high-luminosity ...conditions at LHC. This feature requires frequent transmission measurements over the full ECAL in order to obtain short-term corrections of the measured energies of physics events. Therefore, an optical monitoring system was developed consisting of a laser source and an optical fibre distribution system. The validation of the light injection system with its final laser and read out electronics and the feasibility determining the short-term correction were the main goals of a dedicated test beam during summer 2002. Data were collected with a 400 crystal final production module, partially equipped with electronics (100 channels) for these tests. The monitoring system, its performance and the results obtained during this period are presented.
A first alignment of the LHCb Vertex Locator has been obtained from beam induced tracks at the LHC. A 450
GeV/
c protons were collided on a beam absorber during the LHC synchronisation tests of the ...anti-clockwise beam in August and September 2008. The resulting particle tracks have been reconstructed by the Vertex Locator. This was the first full reconstruction of tracks induced by the LHC beam. The quality of the data obtained is discussed. A total of 2200 tracks were reconstructed from the full data sample, and a first spatial alignment was obtained. The detector is aligned to an accuracy of
5
μ
m
in the sensor plane. The results confirm that all detector modules have not been displaced from their surveyed positions by more than
10
μ
m
.
First LHC beam induced tracks reconstructed in the LHCb VELO Parkes, C.; Borghi, S.; Bates, A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
06/2009, Letnik:
604, Številka:
1
Journal Article
Recenzirano
The Vertex Locator of the LHCb experiment has been used to fully reconstruct beam induced tracks at the LHC. A beam of protons was collided with a beam absorber during the LHC synchronisation test of ...the anti-clockwise beam on the weekend 22nd–24th August 2008. The resulting particles have been observed by the Vertex Locator. The LHCb Vertex Locator is a silicon micro-strip detector containing 21 planes of modules. Tracks were observed passing through up to 19 modules (38 silicon sensors). A total of over 700 tracks were reconstructed, and are being used to study the calibration and alignment of the detector.
The LHCb experiment at LHC, optimised for the study of CP violation, has two RICH detectors to provide particle identification in the momentum range
∼
2
–
100
GeV
/
c
. The stringent requirements on ...the photon detectors are met by the custom-made pixel Hybrid Photon Detector.
The photon detectors need to operate in the fringe field of the LHCb dipole magnet which will produce distortions of the image detected on the pixel chip which is encapsulated inside the HPD. This paper reports on the experimental characterisation of the image distortions caused by an external magnetic flux density. These measurements allow for the development of a parameterisation of the effects and a compensation algorithm, which are also presented.
DNA sequences of both 5′ and 3′ regions of the plastid ndhF gene were generated in order to study the position of Patrinia and Nardostachys, to check the potential paraphyletic nature of Patrinieae, ...and to evaluate the possible link between the tribe and Linnaeaceae. Parsimony analysis showed very strong support for Patrinia as sister to all members of Valerianaceae (including Nardostachys) and indicated the paraphyletic nature of the tribe Patrinieae. Additionally, trees were constructed from available rbcL data separately and supplemented with ndhF sequences. Topologies of these combined cladograms are in agreement with the ndhF phylogeny, suggesting that the traditionally circumscribed Patrinieae can no longer be recognized but must be considered as part of a basal grade in Valerianaceae. Parsimony analysis based on a morphological data set supported a monophyletic Patrinieae; combination with the molecular data showed a paraphyletic Patrinieae. Furthermore, the possible link between Patrinieae and Linnaeaceae is evaluated.
The LHCb experiment requires positive kaon identification in the momentum range 2-100 GeV/c. This is provided by two ring imaging Cherenkov detectors. The stringent requirements on the photon ...detectors are fully satisfied by the novel pixel hybrid photon detector, HPD. The HPD is a vacuum tube with a quartz window, S20 photo-cathode, cross-focusing electron optics and a silicon anode encapsulated within the tube. The anode is a 32/spl times/256 pixels hybrid detector, with a silicon sensor bump-bonded onto a readout chip containing 8192 channels with analogue front-end and digital read-out circuitry. An external magnetic field influences the trajectory of the photoelectrons and could thereby degrade the inherent excellent space resolution of the HPD. The HPDs must be operational in the fringe magnetic field of the LHCb magnet. This paper reports on an extensive experimental characterization of the distortion effects. The characterization has allowed the development of parameterisations and of a compensation algorithm. A calibration procedure based on the imaging of pre-defined test patterns that has been developed for the RICH detectors is also proposed.
LHCb is the dedicated heavy flavour experiment at the Large Hadron Collider at CERN. The partially assembled silicon vertex locator (VELO) of the LHCb experiment has been tested in a beam test. The ...data from this beam test have been used to determine the performance of the VELO alignment algorithm. The relative alignment of the two silicon sensors in a module and the relative alignment of the modules has been extracted. This alignment is shown to be accurate at a level of approximately
2
μ
m
and
0.1
mrad
for translations and rotations, respectively, in the plane of the sensors. A single hit precision at normal track incidence of about
10
μ
m
is obtained for the sensors. The alignment of the system is shown to be stable at better than the
10
μ
m
level under air to vacuum pressure changes and mechanical movements of the assembled system.
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