The Large Hadron Collider
The Large Hadron Collider (LHC) Evans and Bryant, J Instrum 3:S08001, 2008, [1 ] at the European Laboratory for Particle Physics (CERN (See footnote 1)) near Geneva, Switzerland, is a hadron accelerator, designed to provide unprecedented centre-of-mass-en
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The Large Hadron Collider
The Large Hadron Collider (LHC) [1] at the European Laboratory for Particle Physics (CERN1 ) near Geneva, Switzerland, is a hadron accelerator, designed to provide unprecedented centre-of-mass-energies and luminosities for the discovery of new physics. Furthermore, it allows for measurements of parameters of the Standard Model in hitherto inaccessible regions of phase space. A large fraction of the physics programme is based on proton-proton collisions, for which energies of up to 14 TeV and luminosities of more than 1034 cm−2 s−1 are foreseen. In addition, the accelerator provides the possibility of colliding lead (Pb) ions at energies of up to 2.8 TeV per nucleon and luminosities of 1027 cm−2 s−1 . These collisions are used to study the formation of a quark-gluon-plasma under conditions similar to those in the early universe. Section 6.1 gives an overview of the accelerator complex, while Sect. 6.3 gives the definition of the luminosity in terms of collider parameters. The filling scheme of the LHC, which is subject to certain constraints from the pre-accelerator chain, is described in Sect. 6.2. A short overview of the four large LHC experiments is given in Sect. 6.4, and the run-I performance as well as the expectations for run-II are presented in Sect. 6.5.
6.1 The Accelerator Complex Before being filled into the LHC, the protons have to be accelerated. This preacceleration proceeds in several steps, the complete injection chain is shown in Fig. 6.1. The protons are extracted by ionising hydrogen and are first fed into a linear accelerator, Linac2. Subsequently, they pass through the Booster, the proton 1 Conseil
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6 The Large Hadron Collider
Fig. 6.1 The CERN accelerator complex. For a description of the proton acceleration chain see text [2]
synchrotron (PS) and the super proton synchrotron (SPS), and are finally filled into the LHC ring via two transfer lines. Their energy is increased in each step, from 50 MeV after Linac2 to 1.4, 25 and 450 GeV of injection energy into the LHC, where they are to be accelerated to up to 7 TeV per beam. The collider is situated in the 27 km long tunnel that formerly hosted CERN’s Large Electron-Positron Collider (LEP), approximately 100 m underground. The magnetic fields needed to steer the particles around the ring are provided by 1232 superconducting NbTi dipole magnets. They are cooled to a temperature of 1.9 K by superfluid helium and generate fields stronger than 8 T. In addition to the dipole magnets for steering, there are 392 quadrupole magnets for focussing the beams. At the interaction points the two beams are brought into collision with a certain angle, since head-on collisions would result in a large number of parasitic interactions.
6.2 The LHC Bunch Structure The LHC can be operated with different filling schemes. In this section, a bas
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