ANNIE MRD simulation output

WChSandBox currently outputs two files; FullEvent.root and MRDEvents.root. Both have a very similar structure. The FullEvent.root file stores one event tree, containing all start and ending information of particles and photons generated during the simulation, along with some additional run information. The MRDEvents.root file is populated with information obtained from Geant4 'hits' in the sensitive detectors within the MRD (and FACC, once implemented).



  • evt : the event number
  • nphot : the total number of photons generated this event
  • npart : the total number of particles generated this event
  • ncapturecount : the number of neutron capture events identified this event
  • neutroncount : the total number of neutrons generated this event
    There are then nearly identical arrays for particles and photons. The properties are generall self-explanatory:
  • phot_xStart, phot_yStart, phot_zStart, phot_tStart, part_xStart, part_yStart, part_zStart, part_tStart : photon or particle generation position & time.
  • phot_xEnd, phot_yEnd, phot_zEnd, phot_tEnd, part_xEnd, part_yEnd, part_zEnd, part_tEnd : photon or particle position & time at end of tracking.
  • phot_wavelength : self-explanatory
  • phot_isScat : tags whether a photon scatters at least once. This is determined by comparing the momentum direction of the starting and ending points.
  • phot_parentid and part_parentid : parent track ID
  • phot_trackid and part_trackid : track ID
  • phot_hit : Legacy detection of photon hits. Depreciated
    Previously the tank was the world volume, and hit detection was done by recording when a photon 'left' the world volume. This is no longer a suitable hit criteria. The reason all photons read '0' for this (indicating no photons leave the world) is that the world is filled with Air, which is given the optical absorption properties of blacksheet...
  • phot_capnum : If a photon emission (start) time is within 10ns of a capture event, the photon is associated with that capture event.
  • phot_mrdhit : tags whether a photon passed through the MRD.
  • phot_mrdxxx : various template variables, not used. will be stripped in code cleanup
  • part_pxStart : particle initial x momentum. Similar for y,z and End branches.
  • part_KEstart , part_KEend : particle initial and final kinetic energy.
  • part_processStart : numeric indicating the generation process for the particle.
    A complete list of process IDs and their corresponding process, as well as particle IDs and their corresponding particle, can be found at the bottom of the file in the /src/ folder.
  • part_pid : Particle ID. See above.
  • capt_x : x position of a capture. Similar for capt_y, capt_z, capt_t0.
  • capt_E : Energy emitted in gammas from this capture. This is calculated by scanning all gamma particles with a start process of neutron capture, and adding their energy to the corresponding capture record.
  • capt_num : ID of a capture event.
  • capt_pid : appears to be unused.
  • capt_nucleus : particle ID of the non-gamma daughter of the capture event (daughter nucleus)
  • capt_nphot : number of photons associated with (emitted within 10ns of) a capture event
  • capt_ngamma : number of gammas associated with a capture event



  • evt : event number
  • hitnum : number of hits this event apologies for unintuitive naming
  • mrdhit_x, mrdhit_y, mrdhit_z, mrdhit_t : position and time of hit.
  • mrdhit_process : ID of interaction process within the MRD. Same ID convention as above.
  • mrdhit_particleID : ID of interacting particle.
  • mrdhit_trackID : track ID of interacting particle.
  • mrdhit_edep : energy deposition in hit.
  • mrdhit_objnum : depreciated
  • mrdhit_copynum : Geant4 copynumber of physical volume. depreciated


  • evt : event number
  • pmt_hitnum : number of hits on the PMT sensitive detector all PMTs are part of the same sensitive detector
  • pmthit_x, pmthit_y, pmthit_z, pmthit_t : position and time of hit.
  • pmthit_process : ID of the process that created the photon. Same ID convention as above.
  • pmthit_trackID : track ID of hit photon.
  • pmthit_parentID : track ID of parent particle.
  • pmthit_wavelength : self-explanatory
  • pmthit_copynum : identifies which PMT was hit.