LHC fixed target experiments : Report from the LHC Fixed Target Working Groupof the CERN Physics Beyond Colliders Forum

Several fixed-target experiments at the LHC are being proposed and activelystudied. Splitting of beam halo from the core by means of a bent crystal com-bined with a second bent crystal after the target has been suggested in order tostudy magnetic and electric dipole moments of short-lived particles. A similarscheme without the second crystal or other schemes with more conventionalsolid or gas targets have been proposed to study hadronic matter and the quark-gluon plasma, as well as to provide inputs to cosmic ray physics. Most notably,an upgrade of the existing and already productive LHCb gas target (SMOG),which would make use of a storage cell, has been proposed, designed, andextensively reviewed. The implementation in LHCb of a polarised gas tar-get, based on the storage cell technique, was also discussed, motivated by thenucleon-spin study. The status of these proposals, their technical feasibilityand impacts on the LHC machine have been studied in the LHC Fixed TargetWorking Group of the Physics Beyond Collider forum at CERN. The statusand outcome of these studies are presented here.