Physics at HERA

The very high energies offered by HERA permit one to probe deep inside the proton in order to study the structure of its constituents, the quarks and gluons. Following Heisenberg's uncertainty relation a measure for the smallest size D of resolved objects is the transverse momentum kick Q which the electron impacts to the proton, D ~ h/Q (h Plank constant). Q2 values as high as 40000 GeV2 can be reached at HERA corresponding to D = 10E-16 cm which is a factor 1000 smaller than the proton radius. With this resolving power exciting physics topics can be studied, such as substructure of quarks and electrons, neutral and charged current processes, tests of Quantum Chromodynamics, searches for new currents and for new particles.

The success of such studies depends critically on the accuracy with which the energies and angles of the particles and particle bundles (= jets) resulting from the interactions can be measured.

Electron-proton scattering.