GROUP_GEO_TRACKS

Short description

This group contains information about all (charged and neutral) particles observed in the event.

Summary

• Include file: tracking.h
• Data structure:

  typedef struct
  {
    int32      index;         /* 
                               * for TRK_F_MPSTRACK tracks   - index into the tracks_t array
                               * for TRK_F_LGDCLUSTER tracks - index into the array of LGD clusters.
                               * for TRK_F_TCYLTRACK tracks  - index into the array of TCYL tracks
                              */
    int32      vertex;        /* number of the vertex (counting from 0) */
    vector3_t  p;             /* momentum 3-vector in GeV/c  */
    int32      charge;        /* charge (usually -1, 0 or 1) */
    float32    p_cov[3*3];    /* covariance matrix (usually TRK_F_COV2_xxx or TRK_F_COV3_xxx, as set of flags) */
    Particle_t particleType;
    float32    xi2pdf;        /* This xi2pdf is for the fit with the vertex */
    uint32     flags;         /* see TRK_F_xxx flags above */
  } geo_track_t;
  
  typedef struct
  {
    int32       ntracks;
    geo_track_t track[1];
  } geo_tracks_rec_t;
  
  

• Related functions:
  • tracks_event()
• Related data groups:
  • GROUP_GEO_VERTICES
  • GROUP_TRACKS
  • GROUP_LGD_CLUSTERS
  • GROUP_TCYL_TRACKS
• Related Hist histograms:
  • TRKFIT-xxx
  • VTXFIT-xxx
• Related Map Manager items:
  • none
• Source code: Tracking/trackXXX.c

Discussion

xxx

Data structure fields

• ntracks: number of tracks in the data group.
• index: index into the group where the track originated from.
• vertex: index into the GEO_VERTICES group, number of the vertex this track comes from
• p: momentum three-vector for this particle,
• charge: charge of this particle
• p_cov: 3x3 covariance matrix for the momentum. It's meaning is defined by the flags field.
• particleType: particle type.
• xi2pdf: Chi Squared for the track fit. Can also be 0 or +Inf for non-charged tracks.
• flags: Various bitmapped flags:
  • TRK_F_MPSTRACK - this track comes from GROUP_TRACKS. Index points into GROUP_TRACKS, particleType is usually 'Unknown'
  • TRK_F_LGDCLUSTER - this track comes from an LGD cluster. Index point into GROUP_LGD_CLUSTERS, particleType is 'photon'
  • TRK_F_TCYLTRACK - this track comes from GROUP_TCYL_TRACKS. Charge is always zero, momentum magnitude is always 1.0.
  • TRK_F_BEAM - this is the beam track. Particle type is 'pi-'.
  • TRK_F_RECOIL - this is the recoil track, charge and momentum are calculated assuming assuming a charge=+1 target with zero momentum.
  • TRK_F_COV2_PxPy - the p_cov matrix contains the covariance of p.x and p.y. (magnet-off data only!)
  • TRK_F_COV3_pPxPy - the p_cov matrix contains the covariance of 1/pmag, p.x and p.y. (magnet-on data only)

Bugs

• xxx.
• xxx.

//CO 27-DEC-1994