Status of ATLAS and CMS upgrades on calorimetry and timing

The High Luminosity LHC (HL-LHC) will integrate $10$ times more luminosity than the LHC, posing significant challenges for radiation tolerance and event pileup on detectors, especially for forward calorimetry, and hallmarks the issue for future colliders. As part of their HL-LHC upgrade program, the ATLAS and CMS collaborations are replacing the electronics of their calorimeters that provide higher granularity for the level-1 trigger and better measurements of the time of arrival of particles. The CMS collaboration is also designing a High Granularity Calorimeter to replace the existing endcap calorimeters. It features unprecedented transverse and longitudinal segmentation for both electromagnetic and hadronic compartments. This will facilitate particle-flow calorimetry, where the fine structure of showers can be measured and used to enhance pileup rejection and particle identification. In addition, a new dimension in the event reconstruction will be provided by thin timing detectors built between the inner trackers and the calorimeters of both ATLAS and CMS. They will measure the time of arrival of charged tracks with a resolution of $30$ to $40\, \textrm{ps}$ and help reducing the pileup density in space-time down to the level of the Phase 1.