Requirements of Beam Dynamics on the Alignment of the Low-beta Insertions

In the collision configuration, the low-beta section concentrates most of the LHC complexity: largest non-linear perturbations, the long-range (LR) interactions between beams passing the lenses off-axis and the mechanical aperture limit of the machine. A misalignment of the quadrupoles in the low-beta section may therefore have more serious consequences than simple geometrical effects at the collision points. In addition to a loss of luminosity and an enhancement of the background, the LR interactions and the balance between parasitic multipoles and their non-linear correctors could be altered. The approach in this note is to identify the important beam dynamicsvariables that may be perturbed by misalignments and specify tolerances which should guarantee that the nominal performance can be reached.