The LHCb experiment (LargeHadronColliderbeauty experiment) is one of the four big experiments (ALICE, ATLAS, CMS, LHCb) at CERN, which are positioned at the new 27 km long LHC accelerator.The entrance to the experiment is in Ferney-Voltaire in france. All in all the LHCb collaboration has 690 staff members from 15 countries.The hole instalation is 100 m beneath the surface. The construction of the 5600 t heavy detector was finished to a large extent in 2007. In the end of 2008 the start up was carried out with cosmic rays and the first beam of the LHC. First proton proton collisions are planned for autumn 2009.


Angular distribution of the events at LHCb. As can be seen most events are int the forward backward region.

The LHCb detector will make precision measurements of the standard modell of particle physics by measuring the properties of B mesons. Allmost all interesting Events happen along the foreward and backward direction. It will only be measured in foreward direction to use the space in the subterranean caverne in an optimal way. That is the reason why the LHCb has been constructed as a foreward spectrometer, which measures events in an area between 15 and 300 mrad.

The detector is about 21 meters long, 10 meters in height and 13 meters in width. Despite its enormous dimensions the LHCb is rather small compared to its collegues. Because of its special design it consists of some compnents, which can not be found at any other LHC experiment. The luminosity for the LHCb can be adjusted at the LHC between 2 and 5 *1032cm-2s-1. The interaction rate is approximatly 10MHz. That means that 105 b events per second are expected. The ratio between the different hadrons is
B0 : B+- : Bs : &Lambdab &asymp 0.8 : 0.8 : 0.2 : 0.2. In a B meson event there will be approxiamtly 30 charged tracks with the highest track density just around the beam axis. To reconstruct those tracks very sensitive instruments are needed. The LHCb reaches a momentum resulution of better than 1% and a resolution in the impact parameter of better than 50μm.

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