[Halld-offline] Truth info from BCAL hadronic showers

[Will Levine]

Hi offline,
Following up on the issue of "late" energy deposition in hadronic
showers in the BCAL.

There are two different ways that BCAL truth information from hdgeant
is stored: these can be accessed in JANA from the DBCALTruthShower and
the DBCALTruthCell objects. The code that stores this information is
in hitBarrelEMcal() in
sim-recon/src/programs/Simulation/HDGeant/hitBCal.cc

As I understand the code, DBCALTruthShower records every particle that
geant tracks thru the BCAL (with energy greater than 1 MeV). One
DBCALTruthShower for each unique particle in the BCAL. This includes
all secondary shower particles. The particle type, initial energy, and
initial position in the BCAL is recorded for each particle.

DBCALTruthCell just records the energy deposited in a given BCAL cell
without recording which particle was responsible for the energy.
(Again this is "truth" information, before any detector resolution or
readout effects are incorporated).

These two sources of information are not always tremendously helpful.
For example in one single-pion event that has some characteristic
"late hits", we see the following DBCALTruthShower's:

DBCALTruthShower:
 ptype: track: primary:    phi:      r:     z:     t:     p:     E:
-------------------------------------------------------------------
     8      1        1  -1.863  65.042  185.3  4.780  0.571  0.588

Only the primary pion is recorded. There is no record of any secondary
tracks. But when we look at the TruthCell's in the same event:

DBCALTruthCell [truncated]:
 module: layer: sector:     E:       t: zLocal:
-----------------------------------------------
     34      1       1  0.006    71.31    -6.0
     34      1       3  0.027     4.87   -24.4
     34      1       4  0.002     4.79   -26.5
     34      2       1  0.006    33.59   -16.9
     34      2       2  0.018     5.07   -19.6
     34      2       3  0.013     4.98   -21.7
     34      3       1  0.020    28.91   -15.4
     34      3       1  0.005  4301.28   -19.1
     34      3       2  0.023     5.19   -16.6
     34      4       1  0.029     6.45   -13.1
     34      4       1  0.019    73.07   -13.0
     34      4       1  0.004  2219.77   -13.3
     34      4       1  0.039  4301.12   -15.0
     34      5       1  0.017     8.24    -9.6
     34      5       1  0.001  4301.19   -17.1
     34      7       1  0.011    10.44   -21.4

The time is in the second-to-last column. The "on-time" hits have t ~
5 ns. Where are all the late hits coming from? It is not clear. There
must be some tracks that are not recorded in the TruthShower info.

Even in events with a more extensive record of secondary tracks it's
not clear what is responsible for a late hit:

DBCALTruthShower:
 ptype: track: primary:    phi:      r:     z:     t:     p:     E:
-------------------------------------------------------------------
     8      1        1  -2.072  65.042  186.4  4.812  0.572  0.589
    13     22        0  -2.083  65.969  188.5  5.185  0.284  0.982
    14     21        0  -2.083  65.969  188.5  5.185  0.040  0.939
    13     20        0  -2.083  65.969  188.5  5.185  0.173  0.955
     3     19        0  -2.081  65.814  188.1  4.879  0.005  0.005
     3     19        0  -2.083  65.851  188.2  4.884  0.002  0.002
     1     19        0  -2.083  65.852  188.2  4.884  0.001  0.001

Any ideas?

Will