TRT HT correction constants for Ar straws
This MR adds corrections to the number of HT hits in TRT Ar straws when using overlay instead of full digitisation. Supporting slides with plots are available at https://cernbox.cern.ch/s/OkKBRXTjeaRiSCj.
This MR is needed to fix the modelling of TRT PID observables when using overlay (for example photon conversion reconstruction).
Tagging @beddall.