A Large Hadron Electron Collider at CERN Report on the Physics and Design Concepts for Machine and Detector

TLDR

The Large Hadron Electron Collider (LHeC) is a proposed collider that will collide a new 60–140 GeV electron beam with the LHC’s hadron beams. Its physics programme aims to explore the energy frontier by complementing the LHC’s discovery potential with high‑precision deep‑inelastic scattering, probing strong and electroweak interactions, and extending electron‑deuteron and electron‑ion scattering to unprecedented kinematic ranges. The LHeC can be realized as either a ring‑ring or linac‑ring collider, with optics, beam‑dynamics, interaction‑region, magnet, detector, and civil‑engineering studies presented for both options. Compared to HERA, the LHeC will extend the kinematic reach by a factor of twenty in Q² and 1/x, achieve a design luminosity of 10³³ cm⁻² s⁻¹, exceed HERA’s integrated luminosity by two orders of magnitude, can be built within a decade, and will operate concurrently with the LHC’s high‑luminosity phase, offering a major opportunity for particle‑physics progress.

Abstract

The physics programme and the design are described of a new collider for particle and nuclear physics, the Large Hadron Electron Collider (LHeC), in which a newly built electron beam of 60 GeV, up to possibly 140 GeV, energy collides with the intense hadron beams of the LHC. Compared to HERA, the kinematic range covered is extended by a factor of twenty in the negative four-momentum squared, $Q^2$, and in the inverse Bjorken $x$, while with the design luminosity of $10^{33}$ cm$^{-2}$s$^{-1}$ the LHeC is projected to exceed the integrated HERA luminosity by two orders of magnitude. The physics programme is devoted to an exploration of the energy frontier, complementing the LHC and its discovery potential for physics beyond the Standard Model with high precision deep inelastic scattering measurements. These are designed to investigate a variety of fundamental questions in strong and electroweak interactions. The physics programme also includes electron-deuteron and electron-ion scattering in a $(Q^2, 1/x)$ range extended by four orders of magnitude as compared to previous lepton-nucleus DIS experiments for novel investigations of neutron's and nuclear structure, the initial conditions of Quark-Gluon Plasma formation and further quantum chromodynamic phenomena. The LHeC may be realised either as a ring-ring or as a linac-ring collider. Optics and beam dynamics studies are presented for both versions, along with technical design considerations on the interaction region, magnets and further components, together with a design study for a high acceptance detector. Civil engineering and installation studies are presented for the accelerator and the detector. The LHeC can be built within a decade and thus be operated while the LHC runs in its high-luminosity phase. It thus represents a major opportunity for progress in particle physics exploiting the investment made in the LHC.