Dynamic Aperture Studies of the Long-Range Beam-Beam Interaction at the LHC

Long-range beam-beam interactions dictate the choice of operational parameters for the LHC, such as the crossing angle and β∗, and therefore the luminosity reach for the collider. The long-range beam-beam interaction can lead to particle losses, closed orbit effects and emittance growth. Defining how these effects depend on the beam-beam separation will determine the minimum crossing angle and the β∗ the LHC can operate. In this article, analysis from a dedicated machine study is presented in which the crossing angle was reduced in steps and the impact on beam intensity and luminosity lifetimes were observed. Based on the observations during the machine study, the intensity decays are compared to expectations from models. Estimates of the luminosity reach in the LHC are also computed.