Speaker
Description
The extreme pileup conditions expected at the High-Luminosity LHC (HL-LHC) requires new technologies to cope with the higher occupancy. One of the strategies adopted to address this challenge is the usage of precise timing information in event reconstruction. The CMS experiment will introduce two new sub detectors with timing capabilities: the MIP Timing Detector (MTD) covering both barrel and endcap regions and the High-Granularity Calorimeter (HGCAL) in the endcaps only. Together they will provide a resolution in the order of tens of picoseconds, enabling the reconstruction of events in 5 dimensions (x, y, z, E, t).
Time information is being integrated into TICL, the framework developed for the HGCAL reconstruction and integrated in the CMS software. In HGCAL, each sensor with an energy deposit above a certain threshold will have a time information, that is used to compute the time of the 2D and 3D clisters. MTD instead assigns a time information to the tracks for charged candidates. During the linking between energy deposits in the calorimeters and tracks for the tracker, times from HGCAL and MTD are required to be compatible within a threshold to allow the linking. In the end, the time of the final charged candidates is obtained by combining the HGCAL and MTD times, improving the candidate time resolution.
Time information is also being exploited at future colliders, where detectors will features trackers with timing capabilities at each layer and HGCAL-like detetors with a time information for calorimeter hits as well. This opens the path towards 4D clustering, where spatial and temporal hits information are jointly used for pattern recognition, and toward particle-flow algorithms that are time-aware.
This contribution will present the current usage of timing in high energy physics event reconstruction, highlighting the algorithmic strategies enabled by HGCAL and MTD, and outline the evolution toward 4D event reconstruction at CMS and at future colliders.