PRELIMINARY SIMULATIONS OF EMITTANCE GROWTH DUE TO AN EXTERNAL NOISE IN COLLIDING BEAMS IN THE LHC

The upgrade of the LHC from the current set-up to high luminosity performances will provide new challenges from the point of view of beam-beam as well as other collective effects and luminosity levelling. We present the current possibilities for doing luminosity levelling for HL-LHC. We explore the merits and drawbacks of each option and briefly discuss the operational implications. The simplest option being levelling with an offset between the two beams. In particular, we look at the possibility of using flat beams in the IPs for all the available options and investigate their benefits and drawbacks, using the code COMBI. Flat beams would allow an additional degree of freedom, with the levelling only required in one of the planes at any given IP. To this end, various scenarios are looked at, both with and without crab cavities.