Diffraction Phenomena and High Energy Physics

Usually High Energy Physics is considered as the synonym of "physics of particles". New phenomena in this area are related to discoveries of new particles or to the typical "particle-like" effects, such as "Bjorken scaling" in Deep Inelastic Scattering (DIS) or jets with high transverse momenta and so on. In the space-time language these kinematical regimes correspond to small distances.

However there is an area in High Energy Physics, which is related to rather large distances, even at high energies. These phenomena are similar to the scattering of hadrons to small angles. The wellknown feature of such processes is that the angle distribution gives the typical diffractive pattern with zero-angle maximum and one or, sometimes, two dips. Here wave properties of hadrons play the main role. From this distribution we can make the conclusion about size and shape of the scatterer, or the "interaction region".

Experiments at the Large Hadron Collider (LHC) which aim to study regimes with low (TOTEM,) and high (CMS,) transverse momenta, related to typical undulatory (diffractive) and corpuscular (point-like) behavior of the corresponding cross-sections, may offer a very exciting possibility to observe an interplay of both regimes. In theory the "hard part" can be (hopefully) treated with perturbative methods while the "soft" part is definitely nonperturbative.

Several examples of such an interplay have been analyzed: exclusive Standard model Higgs boson production by diffractively scattered protons, exclusive double diffractive events (EDDE) with production of two gluon jets, graviscalar (Radion) and Higgs boson (Randall-Sundrum model), light mesons and gravitons.

Last updated on 27.09.2009. Send your comments and suggestions on this page to Roman Ryutin