Photon pointing

Added photon pointing w.r.t. the hardest vertex by default in the PhotonSelectorAlg, as it appears both yybb PHYS and PHYSLITE files compute photon kinematics w.r.t. (0,0,0). Adding this leads to much better agreements in myy when comparing to the legacy analysis ntuples (MxAODs).

Relevant check on PHYSLITE: https://atishelm.web.cern.ch/atishelm/Research_Updates/yybb/24_October_2023_Investigating_PHYSLITE_for_yybb_updatedStatsAndPlots.pdf

Note: This has been made the default behavior in PHYSLITE as of 24.2.28:

JIRA: https://its.cern.ch/jira/browse/ATLASG-2621
Athena MR: atlas/athena!66871 (merged)

Files edited:

• EasyjetHub/src/PhotonSelectorAlg.cxx:

  • Added vertex container and egammaUtils containing the new tool.
  • Search for primary vertex (nominally defined as vertex with highest sum pT squared), then correct each photon if m_recomputePhotons set to true (be default, it is set to true, as one should only do something different if they know they need photon kinematics reconstructed w.r.t. another vertex).

• EasyjetHub/src/PhotonSelectorAlg.h:

  • Added vertex container key for use in EasyjetHub/src/PhotonSelectorAlg.cxx
  • Defined new variable m_recomputePhotons, configurable when PhotonSelectorAlg is called.

• EasyjetHub/CMakeLists.txt:

  • Added egammaUtils to use new correction tool.

HHframework contacts: @tstreble @lderamo

It would be great to have at least one person from the yybb team look at this to make sure it makes sense from the yybb point of view, e.g. @losanti or @smeriano