HERA (particle accelerator)

[1][2] At HERA, electrons or positrons were brought to collision with protons at a center-of-mass energy of 320 GeV.

[3] HERA was used mainly to study the structure of protons and the properties of quarks, laying the foundation for much of the science done at the Large Hadron Collider (LHC) at the CERN particle physics laboratory today.

HERA is the only lepton–proton collider in the world to date and was on the energy frontier in certain regions of the kinematic range.

To collide protons with either electrons or positrons, HERA used mainly superconducting magnets, which was also a world first.

These groups developed, constructed and ran the multi-storey, complex measurement devices in many years of cooperative work and evaluated enormous amounts of data.

Leptons (electrons or positrons) were pre-accelerated to 450 MeV in the linear accelerator LINAC II.

Protons were obtained from originally negatively charged hydrogen ions and pre-accelerated to 50 MeV in a linear accelerator.

The transverse polarimeter was upgraded in 2001 to provide a fast measurement for every positron bunch, and position-sensitive silicon strip and scintillating-fibre detectors were added to investigate systematic effects.

Today, a section of the HERA tunnel and 24 former superconducting dipole magnets are being used for the new ALPS experiment, which looks for axion-like particles.

Due to the enormous scope of the HERA project, many international institutions agreed to participate already in the construction.

It was designed for probing the inner structure of the proton, the exploration of the strong interaction as well as the search for new kinds of matter and unexpected phenomena in particle physics.

A small segment of the HERA tunnel. The proton beam is travelling in the large vacuum tube in the middle to the right, the electron beam tube is below that.
The EW interaction is mediated to first order therefore when the momentum transfer-squared becomes bigger than the mass of the charged W and the neutral Z boson squared (< 10 4 ) the magnitude of their differential cross sections become comparable so the charged and neutral currents (CC (red) & NC (blue)) appear indistinguishable but it also becomes lower so they look hard to distinguish from the massless photon too, that is EW unification starts to set in. [ 4 ] [ 5 ] [ 6 ]