Track association to MC particles

• Definition, Track Þ MC particles
• Definition, cluster Þ MC particles
• Definition, hit Þ  MC
• Implementation
   

UNDER CONSTRUCTION !

Definition, Track Þ MC particles:

• VELO part:
  If  ³70% of the clusters are associated to the same MC particle, then the VELO part is associated to a MC particle (id_velo).
• TT part:
  If  all clusters except one are associated to the same MC particle, then the TT part is associated to a MC particle (id_TT).
• T part:
  If  ³70% of clusters are associated to the same MC particle, then the T part is associated to a MC particle (id_T).
   
• Long tracks:             id_velo == id_T, no check on id_TT
  Exception:                If the MC particle in T(id_T) is a daughter of the MC particle in the VELO(id_VELO), then the track is associated to both MC particles.
• Upstream tracks:      id_T     == id_TT
• Downstream tracks: id_velo == id_TT
• Else,  track is defined as a ghost.

Definition, cluster Þ MC particles:

• Sum of associations of the hits to MC particles inside a cluster.

Definition, hit Þ MC:

• VELO: A MC particle is related to a MCVeloFE if it contributes > 10% of  VeloSimParams::threshold.
  The VeloSimParams::threshold value is by default 4500 electrons.
• ST     : A MC particle is related to a digit if it contributes more than 10% to the total deposited charge.
• OT    : Any MC particle having a MCHit in OT is associated to an OTDigit. (Can there be more than one MC particle associated to the same OTDigit ?).
• TO BE KEPT IN MIND: Hits from spillover events have by default no link to the MC truth, therefore any track reconstructed from a spillover MC particle is a ghost.

Implementation:

• NEW: linkers, see Olivier Callot presentation during software week: Usage of Linker for relations
• Associators, LHCb-2004-022

TR 27/02/2006