Deep inelastic electron-nucleon scattering at the LHC

Abstract

The physics, and a design, of a Large Hadron Electron Collider (LHeC) are sketched. With high luminosity, 10 33 cm −2 s −1 , and high energy, √ s = 1.4 TeV, such a collider can be built in which a 70 GeV electron (positron) beam in the LHC tunnel is in collision with one of the LHC hadron beams and which operates simultaneously with the LHC. The LHeC makes possible deep-inelastic lepton-hadron (ep, eD and eA) scattering for momentum transfers Q 2 beyond 10 6 GeV 2 and for Bjorken x down to the 10 −6 . New sensitivity to the existence of new states of matter, primarily in the lepton-quark sector and in dense partonic systems, is achieved. The precision possible with an electron-hadron experiment brings in addition crucial accuracy in the determination of hadron structure, as described in Quantum Chromodynamics, and of parton dynamics at the TeV energy scale. The LHeC thus complements the proton-proton and ion programmes, adds substantial new discovery potential to them, and is important for a full understanding of physics in the LHC energy range.

Deep inelastic scattering at the TeV energy scale and the LHeC project

“…In contrast, with detector components restricted to θ < 170 • , there is little acceptance for Q 2 < 100 GeV 2 or x < 10 −4 . Optimising the luminosity by including beam focusing elements close to the interaction region [ 3,7], similar to those installed for the upgrade from HERA-I to HERA-II, must therefore be evaluated against the implications of the corresponding loss of small angle detector acceptance.…”

“…However, since leptoquarks are almost always pair-produced at the LHC, unravelling their potentially complex spectroscopy [ 12] would be difficult. The more easily controlled single production vertex in ep physics allows fermion number to be determined for example from electron beam charge asymmetries, spins from angular decay distributions and chirality from beam polarisation asymmetries [ 3]. Another exotic scenario to which the initial state lepton at the LHeC gives high sensitivity is the production of excited leptons, as illustrated in figure 3c.…”

“…3 Studying inclusive diffraction at the LHeC may therefore best be done by directly detecting scattered protons. Given that the beam optics for outgoing protons at the LHeC would not be very different from those at the LHC, first considerations [ 43] suggest that that the region around 420 m from the interaction point would be a suitable place to install a beamline proton spectrometer, similar to that under consideration by ATLAS and CMS [ 44].…”

“…It is reasonable to ask whether these proton beams could be exploited as part of a new high performance ep and electron-ion (eA) 'Large Hadron electron Collider' (LHeC) [ 3,4], complementing the LHC pp and AA programme and a possible pure lepton collider at the TeV energy scale.…”

“…Open areas correspond to possible upgrade scenarios. The values shown for the LHeC are for the configuration described in [ 3].…”