The TOTEM (Total Cross Section, Elastic Scattering and Diffraction Dissociation) experiment measures the total pp cross-section and study elastic and diffractive scattering at the LHC.

Modest in size, TOTEM is installed near the point where protons collide in the center of the CMS detector. It uses silicon sensors installed in the LHC tunnel approximately 200 meters away from CMS.

The experiment measures particles scattering at very small angles from the LHC's proton-proton collisions, allowing scientists to study physical processes that can’t be studied by the other LHC experiments, such as how the shape and size of a proton varies with energy.

TOTEM scientists will study inelastic proton-proton collisions in which one proton survives and the other disintegrates and produces "debris" that continues traveling forward. They will also measure elastic collisions in which both protons survive and only slightly deflect each other.

The TOTEM experiment uses three detector types: Roman Pots with microstrip silicon detectors used to detect protons; and Cathode Strip Chambers and GEM Detectors that will measure the jets of forward-going particles that emerge from collisions when the protons break apart.

The TOTEM collaboration comprises some 80 physicists from 11 universities and laboratories in eight countries.