Advances in transverse beam halo characterization and implications for HL-LHC

Measurements of the transverse beam halo in the LHC showed that it contains a non-negligible portion of the total stored beam energy, with implications for both collimation system performance and overall machine protection. As the HL-LHC era, with a significant increase in stored beam energy approaches, the understanding and modelling of the beam halo distribution becomes even more important. This applies particularly for the risk quantification in view of new failure scenarios. This contribution summarizes the recent progress in beam halo measurement, new findings from refined analysis methods, an overview of the employment of key measurement techniques, and advancements in experiments aiming to quantify the origin of beam halo. We describe the latest halo models and how they affect the performance of potential active halo control mechanisms in simulations. These developments form a critical input to HL-LHC machine protection strategies.