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LHCb successfully installs its precision silicon detector, the Vertex Locator
:: 13 November, 2007
12 November 2007. One of the most fragile detectors for the Large Hadron Collider beauty (LHCb) experiment has been successfully installed in its final position. LHCb is one of four large experiments at CERN’s Large Hadron Collider (LHC), expected to start up in 2008. For the LHCb collaboration, installing the Vertex Locator (VELO) detector into its final location in the underground experimental cavern at CERN has been a challenging task.
This milestone marks the fruition of the construction phase of the VELO project. “It was a very delicate operation”, said Paula Collins, LHCb-VELO project leader, “With its successful completion, the VELO is now in place and ready for physics.”
The VELO is a precise particle-tracking detector that surrounds the proton-proton collision point inside the LHCb experiment. At its heart are 84 half-moon shaped silicon sensors, each one connected to its electronics via a delicate system of more than 5000 bond wires. These sensors will be located very close to the collision point, where they will play a crucial role in detecting b quarks, to help in understanding tiny but crucial differences in the behaviour of matter and antimatter.
The sensors are grouped in pairs to make a total of 42 modules, arranged in two halves around the beam line in the VELO vacuum tank. An aluminum sheet just 0.3 mm thick provides a shield between the silicon modules and the primary beam vacuum, with no more than 1 mm of leeway to the silicon modules. Custom-made bellows enable the VELO to retract from its normal position of just 5 mm from the beam line, to a distance 35 mm. This flexibility is crucial during the commissioning of the beam as it travels round the 27-km ring of the LHC.
“The installation was very tricky, because we were sliding the VELO blindly in the detector,” said Eddy Jans, VELO installation coordinator. “As these modules are so fragile, we could have damaged them all and not realized it straight away.” However, the verification procedures carried out on the silicon modules after installation indicated that no damage had occurred.
The VELO project has been ongoing for the past 10 years, involving several institutes of the LHCb collaboration, including Nikhef, EPFL Lausanne, Liverpool, Glasgow, CERN, Syracuse and MPI Heidelberg.
About CERN
The European Organization for Nuclear Research is the world's largest particle physics laboratory, situated just northwest of Geneva on the border between France and Switzerland. The convention establishing CERN was signed on 29 September 1954. From the original 12 signatories of the CERN convention, membership has grown to the present 20 member states. Its main function is to provide the particle accelerators and other infrastructure needed for high-energy physics research. Numerous experiments have been constructed at CERN by international collaborations to make use of them.
About LHCb
The LHCb (standing for "Large Hadron Collider beauty where beauty refers to the bottom quark") experiment is one of six particle physics detector experiments being constructed on the Large Hadron Collider accelerator at CERN. LHCb is a specialist b-physics experiment, particularly aimed at measuring the parameters of CP violation in the interactions of b-hadrons (heavy particles containing a bottom quark).
The fact that both B hadrons are predominantly produced in the same forward cone as B meson production is exploited in the layout of the LHCb detector. The LHCb detector is a single arm forward spectrometer with a polar angular coverage from 10 mrad to 300 mrad in the horizontal and 250 mrad in the vertical plane. The asymmetry between the horizontal and vertical plane is determined by a large dipole magnet with the main component in the vertical direction.
Note for vertex detector
The vertex detector (known as the vertex locator or VELO) is built around the proton interaction region. It is used to measure the particle trajectories close to the interaction point in order to precisely separate primary and secondary vertices, e.g. for B-tagging.
Directly after the vertex detector, a RICH-1 (a Ring imaging Cherenkov detector) is located. It is used for particle identification of low-momentum tracks.
The main tracking system is placed before and after the dipole magnet. It is used to reconstruct the trajectories of charged particles and to measure their momenta.
Release link: http://lhcb.web.cern.ch/lhcb/
Tags: Large Hadron Collider beauty (LHCb) , cern , Large Hadron Collider (LHC) , Vertex Locator (VELO) , Paula Collins , physics , silicon , sensors , b quarks , Eddy Jans , collaboration , Nikhef , EPFL Lausanne , Liverpool , Glasgow , Syracuse , MPI Heidelberg. ,
