LHCb - measuring beauty
When is a VELO not a bike? When it's something a bit more complex, like the vertex detector of the LHCb experiment. VELO stands for VErtex LOcator, and its Technical Design Report was presented, along with that for the experiment's muon detector, in July.
In this prototype of LHCb's vertex locator, VELO, three stations have been equipped with silicon detector elements which are clearly visible in the centre.
The main job of LHCb's VELO will be to look for beauty mesons produced in LHC proton-proton collisions. It is a key element in allowing LHCb to make the definitive measurement of CP-violation, a phenomenon linked to the apparent imbalance between matter and antimatter in the Universe.
When protons collide in the LHC, lots of particles will be created and beauty mesons will be among the hardest to find because their short life will be entirely spent close to the beam axis. That means that to measure them, LHCb has to put detectors to within about eight millimetres of the beam - almost grazing the beam trajectory itself.
Two vacuum chambers will contain the VELO and hold its sensitive silicon detector elements out of the way of the circulating beams while they are being injected and stabilised. That's important to protect them from damage, since the LHC beams will carry the energy of a Boeing 747 travelling at about 400 kilometres per hour. Once stable colliding beams have been established, the silicon elements will move in towards the beam to begin their beauty meson hunt. Radiation resistant electronics will also be included inside the vacuum chambers to process the data from the VELO's 200 thousand readout channels and pass on interesting information for further processing off-line.
