The Role of Noise on Beam Stability and Performance in HL-LHC

The beam response to an external excitation may result in a growth of the emittance, or more generally a modification of its particle distribution. The former reduces the luminosity, and the latter might lead to a loss of Landau damping of coherent instabilities. The corresponding beam dynamics model, experimental studies at the LHC as well as extrapolations to the HL-LHC are discussed in this chapter.