Modelling and Measurements of Bunch Profiles at the LHC

At the LHC, the interplay between a series of effects (e.g. intrabeam scattering, longitudinal beam manipulations, machine non-linearities) can lead to a tails population change, that may result in non-Gaussian beam distributions. Since the calculated beam size depends on the tail formation, it is important to follow the bunch profile evolution. In this paper, the benchmarking of a Monte-Carlo simulation code able to track 3D particle distributions, with the analytical IBS formulas is discussed. Novel distribution functions are employed to describe the beam profiles, and are used as a guideline for generalizing emittance estimations due to IBS and radiation effects. The impact of the distribution shape on the evolution of the bunch characteristics is studied. Bunch profile observations from the LHC Run 2 are compared to simulations and analytical results.