[Halld-offline] DBCALTruthShowers
Justin Stevens
jrsteven at mit.edu
Mon Oct 20 09:05:27 EDT 2014
Hi Richard, All,
Thanks for the fix and reporting it here. I would like to propose two additional changes:
1) When the scheme for keeping track of particle geneology was updated last year, hitCDC.c and hitFDC.c were changed to label the truth hits by their global track ID in the new scheme instead of the internal geant track ID. I suggest we do the same for hitBCAL.cc and hitFCAL.c using something like
showers->in[0].track = gidGetId(track);
This way the truth showers can be matched to DMCThrown objects and their parentage tracked accurately in more complicated events (eg. bggen).
2) In gustep.F there are two places (code pasted at the bottom of this message) where particles are checked to be in the BCAL or FCAL to decide whether to: a) place secondaries on the stack and b) save the vertex and decay particles.
Currently, the checks for the BCAL is if radius < 65 and (cnames(NLEVEL).ne.'BCAL'). To be consistent with the correction for the aluminum plate on the front of the BCAL, I think these should be changed to radius < 64.2485 (?) and (cnames(NLEVEL).ne.'BCAL').and.(cnames(NLEVEL).ne.'BCAM'). Do you agree?
Thanks,
Justin
gustep.F code snippet:
* Place any secondaries generated during this step onto the stack
if (nosecondaries.eq.0) then
do i=1,NGKINE
c make primary except if in calorimeter volume and not hadronic
c interaction, or except if produced in cave upstream of Hall D
iflgk(i) = 1
cint = KCASE
rx = sqrt(VERT(1)**2+VERT(2)**2)
if ((((rx>65.).and.((VERT(3)>-17.).and.(VERT(3)<390.))) !BCAL
> .or.(VERT(3)>625.) !FCAL
> .or.(VERT(3)<-500.)) !CAVE
> .and.(cchar.ne.'HADR')) then
iflgk(i) = 0
endif
call GSKING(i)
enddo
endif
* check if particle did decay in which case save vertex and particles
if (ISTOP .eq. 1) then
mechanism = KCASE
if ((NGKINE>0) .and. (chcase.eq.'DCAY')) then
if ((cnames(NLEVEL).ne.'BCAL').and.
+ (cnames(NLEVEL).ne.'FCAL').and.
+ (sqrt(VERT(1)**2+VERT(2)**2)<65.).and.
+ (VERT(3)<500.).and.(VERT(3)>-500.)) then
call savenewvertex(KCASE,NGKINE,GKIN,VECT,
+ TOFG,iflgk,IPART,ITRA,ISTAK)
endif
endif
endif
On Oct 17, 2014, at 7:12 PM, Richard Jones wrote:
> Hello Justin,
>
> You are right to be surprised by this behavior. It was not there when I first set up this "truth shower" recording mechanism in hdgeant. I looked into it, and was able to reproduce what you are seeing.
>
> The problem is unique to the bcal. It came about primarily (there was another minor issue that I fixed at the same time, that will reduce the fragmentation of the fcalTruthShower info as well) because at some point we added a relatively thick aluminum structure to the front of the bcal, which serves as a primary mechanical support for the module. Because of its thickness, a large fraction of the incident gammas convert and preshower in this aluminum bar, and so what actually reaches the first active layer of the bcal is often a gazillion low-energy shower particles clustered around the incident gamma direction. That is why you were seeing fragmentation in the bcalTruthShower tags.
>
> I added a fix to gustep.F in the HDGeant directory in both the trunk and commissioning branches. Please check out the latest update of whichever you are using and try it. This code catches any particles incident on the bcal and records the TruthShower info before they enter the aluminum support beam. There are still a few conversions that take place in the CDC and the FDC cables around the CDC, but you should see that most of your 2 GeV gammas at 50 degrees now generate just a single bcalTruthShower in hdgeant. For those that shower in the CDC and FDC cable material, I think we should not try to merge them into a single bcalTruthShower because the magnetic field will have a significant dispersive effect on them.
>
> Thank you for reporting this problem. I hope this helps with bcal reconstruction.
>
> -Richard Jones
>
> On Tue, Oct 14, 2014 at 3:30 PM, Justin Stevens <jrsteven at mit.edu> wrote:
> Hi Richard,
>
> I was hoping to follow up on what we talked about briefly at the collaboration meeting regarding BCAL truth showers. I'm looking at some simulation events with single photons generated at theta = 50 degrees and E = 2 GeV. From an earlier thread about hadronic showers on the offline list https://mailman.jlab.org/pipermail/halld-offline/2014-May/001677.html
>
> > Once a primary particle has entered the BCAL and had its TruthShower recorded, it is marked with a spot of red dye (colloquially). Any secondaries that are generated from interactions by that particle inherit its red spot, even if they escape from that module and enter another one.
>
>
> I was expecting there should be only one BCAL truth shower in each event which contain a single photon. This is the case for some events like this one from hd_dump:
>
> DBCALTruthShower:
> ptype: track: primary: phi: r: z: t: p: E:
> -------------------------------------------------------------------
> 1 1 1 -1.419 65.042 119.6 2.832 2.000 2.000
>
> However, for most events there are many DBCALTruthShowers listed, like in the example below:
>
> DBCALTruthShower:
> ptype: track: primary: phi: r: z: t: p: E:
> ------------------------------------------------------------------
> 1 1 1 0.686 65.042 119.6 2.832 2.000 2.000
> 3 3 0 0.686 66.617 120.9 2.901 1.595 1.595
> 3 3 0 0.686 66.979 121.2 2.917 0.001 0.001
> 1 3 0 0.686 66.766 121.0 2.907 0.054 0.054
> 2 2 0 0.686 66.617 120.9 2.901 0.405 0.405
> 1 2 0 0.686 66.894 121.1 2.913 0.018 0.018
> 1 2 0 0.686 66.806 121.1 2.909 0.005 0.005
> 1 2 0 0.686 66.709 121.0 2.905 0.201 0.201
> 3 2 0 0.686 67.005 121.2 2.918 0.158 0.158
> 1 2 0 0.686 67.021 121.2 2.918 0.068 0.068
> 2 2 0 0.686 67.005 121.2 2.918 0.042 0.042
> 1 2 0 0.686 67.060 121.3 2.920 0.016 0.016
> 1 2 0 0.686 67.021 121.2 2.918 0.001 0.001
>
> So first of all, is this the expected behavior? That there are many DBCALTruthShowers where many of them appear to be secondaries of the primary single generated photon in the event?
>
> And if the answer to the questions about is yes, for a general bggen event (where there are many particles incident to the BCAL) how should I best associate reconstructed BCAL showers with these DBCALTruthShowers?
>
> Thanks,
> Justin
>
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