Estimation of the Performance of a HERMES-type Gas Target Internal to the LHC

A storage cell target is capable of producing a high areal density at minimum gas flow into a vacuum system. At the LHC, such a target with polarized hydrogen atoms might be employed for the study of single-spin asymmetries in ultra-relativistic fixed-target pp collisions, or similar light-ion reactions with spin. Another application could be to inject heavy noble gases like Xe (M ≈ 131) in conjunction with a Pb beam to investigate Heavy Ion collisions. A storage cell target with polarized hydrogen or deuterium atoms has been operated successfully in the HERA 27.6 GeV electron beam by the HERMES collaboration. In a recent study by C. Barschel et al, the performance of a HERMES-type storage cell target combined with the full LHC beams has been estimated. In the present talk, the estimates and underlying assumptions are presented in detail. The luminosities obtained are for pp collisions of the order 10 33 /cm 2 s, and for HI collisions of the order of or above the Pb-Pb collider design value of 10 27 /cm 2 s. An alternative scheme to extract the LHC beam halo by Bent Crystals and to direct it onto a solid polarized target is discussed and the figure of merit (FoM) for both methods is presented. It appears that the polarized storage cell target offers a much higher FoM as compared with the bent-crystal scheme.