[Halld-offline] FCAL reconstruction

[Kornicer, Mihajlo]

Hi Beni and David,

I have checked in a quick fix for the vertex problem in the 
DFCALPhoton_factory. I agree that DFCALPhoton is kind of obsolete, but 
you cannot ignore it for now, because cluster energy and position in 
the calorimeter are determined by this factory.

My proposal is to migrate DFCALPhoton into DFCALShower, and use it in 
Vertex and ParticleSet factories, instead of FCALCluster, which is not 
calibrated.
In that way both BCAL and FCAL will have the same objects: clusters for 
initial reconstruction and showers with energy and position info.
If this sound reasonable, I can do this.
Later, one can use true vertex to recalibrate photon position if 
needed, but I assume this will be a second order effect on photon 
momenta in the forward.

Regards,
Mihajlo

Quoting Beni Zihlmann <zihlmann at jlab.org>:

> Hi Mihajlo,
> I just talked also with David because I noticed that he put that
> piece of code in.
> He is looking into it. However he also said that DFCALPhoton is kind
> of obsolete
> and one should use DParticleSet when analyzing and event. This lead to more
> discussion between Simon, Elton, David and me realizing that there is some
> ambiguity in the code regarding photons, calorimeter clusters and tracks from
> tracking because they are interlinked with each other. To resolve this the
> DParticleSet has been introduced. I will go ahead and try to use this to see
> what comes out.
>
> thanks for the fast response,
> Beni
>
>
>>
>> Hi Beni,
>>
>> I have also discovered that feature recently. I guess the idea was
>> to not have photon momenta without the vertex, which is fine, but it
>> cripples the library if you want to look at energy and position in
>> the calorimeter. I'll soon let you know when I submit a fix that
>> uses internal vertex parameter, so you can check it out. More
>> comprehensive solution would be to replace DFCALPhoton with
>> DFCALShower in the future.
>>
>> Regards,
>> Mihajlo
>>
>> Quoting Beni Zihlmann <zihlmann at jlab.org>:
>>
>>> Hi Mihajlo,
>>> I have a problem with the photon reconstruction in the FCAL.
>>> I use a particle gun to shoot photons at the FCAL but I never
>>> get a reconstructed photon. The reason seems that in the
>>> DFCALPhoton_factory there is an if statement checking if
>>> a vertex is available if not the code returns without doing
>>> anything.
>>>         const DVertex *vertex=NULL;
>>>         //loop->GetSingle(vertex);
>>>         vector<const DVertex *>vertices;
>>>         eventLoop->Get(vertices);
>>>         if (vertices.size()) vertex=vertices[0];
>>>
>>>         // If no DVertex object exists, then we cannot calculate the
>>>         // momentum vectors of the photons. We punt here and refuse
>>>         // to make any DFCALPhotons.
>>>         if(vertex==NULL)return NOERROR;
>>>
>>>
>>> do you have an idea how to get around this problem.
>>>
>>> thanks,
>>> Beni
>>>
>>
>>
>
>