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

Abstract

The physics programme and the design are describedof a new collider for particle and nuclear physics,the Large Hadron Electron Collider (LHeC),in which a newly built electron beam of 60 GeV, to possibly 140 GeV, energy collides with the intense hadron beams of the LHC. Compared to the first ep collider, HERA,the kinematic range covered is extended by a factor of twenty in thenegative four-momentum squared, Q2, and in the inverse Bjorken x,while with the design luminosity of1033 cm-2 s-1 the LHeCis projected to exceed theintegrated HERA luminosity by two orders of magnitude. The physics programme is devoted to an explorationof the energy frontier, complementing the LHC andits discovery potential for physics beyond the Standard Modelwith high precision deep inelastic scatteringmeasurements. These are designed toinvestigate a variety of fundamental questions in strongand electroweak interactions. The LHeC thus continues the path of deep inelasticscattering (DIS) into unknown areas of physicsand kinematics. The physics programme also includes electron-deuteron and electron-ionscattering in a (Q21/x)range extended by four orders of magnitudeas compared to previous lepton-nucleus DIS experimentsfor novel investigations of neutron's and nuclear structure, the initial conditions of Quark-Gluon Plasma formationand further quantum chromodynamic phenomena.The LHeC may be realised either as a ring-ring or as a linac-ringcollider. Optics and beam dynamicsstudies are presented for both versions, along with technical designconsiderations on the interaction region, magnets includingnew dipole prototypes,cryogenics, RF, and further components.A design study is also presented of a detector suitableto perform high precision DIS measurements in a widerange of acceptance using state-of-the art detectortechnology, which is modular and of limited size enablingits fast installation. The detector includestagging devices for electron, photon, protonand neutron detection near to the beam pipe.Civil engineering and installation studies arepresented for the accelerator and the detector.The LHeC can be built within a decade and thusbe operated while the LHC runs in its high-luminosity phase.It so represents a major opportunity for progress in particle physicsexploiting the investment made in the LHC.