Mattione Update 06202011

b1pi Overview

• Generated 10000 X(2000) -> b₁π^-; events following the instructions here.
• Decay chain:

 gamma p -> p X(2000)0
               |
               |-> b1(1235)+ π-
                    |
                    |-> ω π+
                          |
                          |-> ρ0 π0
                               |   |-> γ γ
                               |
                               |-> π+ π-

b1pi Event Count

# Generated events = 10000

# Events with 2+ photons = 9660
# Events with 2+ π+'s = 7642
# Events with 2+ π-'s = 8156
# Events with 2+ protons = 1040 (should only be 1 !!)
# Events with enough tracks for the X (2+ photons, 2+ π+'s, 2+ π-'s) = 6076

b1pi Invariant Masses

Classes

Current Class Structure

                                    DPhysicsEvent
                                         |
                               vector < DParticleSet >
                                  /      |       \
 vector < DVertex::shower_info_t >    DVertex     vector < vector < DVertex::track_info_t > > (one for each charged particle id)
                                    /    |    \
                                   /     |     \
  vector < DVertex::shower_info_t >    Misc.    vector < vector < DVertex::track_info_t > >
              /                \                                /         |           \
         DBCALShower       DFCALShower                tprojected    DTrackTimeBased    FOM

* DVertex::shower_info_t is a class that inherits from DKinematicData
* DVertex::track_info_t is a struct
* vector < vector < DVertex::track_info_t > > : for each DTrackCandidate there are multiple fit hypotheses, corresponding to different particle masses

• Problems:
  • Storing final track information in DVertex subclasses is non-intuitive (especially the 2D track_info_t vector).
  • DVertex::track_info_t does not inherit from JObject: cannot add associated objects (DTOFPoint, etc.)
  • Cannot call JEventLoop->Get(DVertex::track_info_t) (No factories for the particles)
  • All neutral particles are assumed to be photons (could be neutrons, such as from Lambda decay).

Proposed Class Structure

                                             DPhysicsEvent
                                                  |
                                        vector < DParticleSet >
                                           /      |       \
                   vector < DNeutralTrack >    DVertex     vector < DChargedTrack >
                                             /    |    \
                                            /     |     \
                    vector < DNeutralTrack >    Misc.    vector < DChargedTrack >
                              |                                        |
          vector < DNeutralTrackHypothesis >             vector < DChargedTrackHypothesis >
           /             |             \                      /            |             \
 FOM, tprojected, DKinematicData, Particle_t         FOM, tprojected, DTrackTimeBased, Particle_t

* Particle_t is an enum defined in libraries/include/particleType.h that is used to store the particle id (values = Proton, PiPlus, etc.)
  * It uses the GEANT particle ID scheme. 

Notes:
 - In the proposed scheme DPhoton, DBCALPhoton, and DFCALPhoton would no longer be supported.  
 - One DNeutralTrackHypothesis would be generated for each combination of DVertex and mass hypothesis, each with a FOM. 
 - The particle objects (DChargedTrack, DChargedTrackHypothesis, DNeutralTrack, and DNeutralTrackHypothesis) will store 
   the objects they are matched with (DBCALShower, DFCALShower, DTOFPoint, and DVertex) as associated objects.  
 - Simulations of the fractional energy deposited by neutrons in the calorimeters are needed to implement neutron energy
   reconstruction and identification.