Total Cross Section, Elastic Scattering and Diffraction Dissociation at the LHC

TOTEM is an experiment dedicated to the measurement of total cross section, elastic scattering and diffractive processes at the LHC. The total cross section will be measured using the luminosity independent method which is based on the simultaneous detection of elastic scattering at low momentum transfer and of the inelastic interactions. This method also provides an absolute calibration of the machine luminosity. The experimental apparatus consists of: \begin{itemize} \item Telescopes of "Roman pots" placed symmetrically on both sides of the crossing region. They will detect protons scattered at very small angles in elastic or quasi-elastic reactions. \item A forward inelastic detector covering 4 pseudorapidity units in the forward cones (from $\eta$ = 3 up to $\eta$ = 7) with full azimuthal acceptance. This detector will measure the overall rate of inelastic reactions. \end{itemize} In the present configuration 3 stations of Roman pots are foreseen on each side of the crossing region. Using the machine optics which have been studied until now, elastic scattering will be measured on a large range of momentum transfer, from 0.01 GeV$^2$ up to about 10 GeV$^2$. The experiment will be installed in IP5. The inelastic detector of TOTEM will be integrated with the experiment CMS realizing a tracking system that covers also the forward cones. The basic components are planes of cathode read out chambers used to reconstruct the collision vertex. The trigger is provided by a system of resistive plate chambers (RPC). The inelastic detector of TOTEM will be calibrated during the total cross section runs, thus providing an absolute monitor of the machine luminosity in IP5.