[Halld-offline] Particle Class Structure

[Matthew Shepherd]

Hi Paul,

It would be interesting to take a sample event say:

gamma p -> K+ Ks pi^0 n, where Ks -> pi+ pi-

an event with 3 tracks, two photons, and one neutron, and then illustrate what the DPhysicsEvent would look like and the algorithm for populating it.  To simplify things you can assume the detector is perfect and there are no extra tracks or photons.  The tracking software has given you 3 tracks each with a kaon and pion fit.  The calorimetry code has provided three showers.  What is is done next?

Some comments/questions:

This is a case where you can imagine having two "Particle Sets" one primary set:  K+ pi^0 n:  that's three neutral "tracks" one one charged track.  And a second set that is two charged pions.  However, won't every neutral track be listed in every DVertex (with presumably different FOM) since it is impossible to distinguish which vertex the neutral came from?

Also, how will multiple DParticleSets in an event be determined?  What decision algorithm will be used to separate the pi+ pi- from the other K+ in the event?

Since you are aiming to collect information and not do analysis tasks I wonder if it would be simpler just to have the physics event be a list of charged tracks and neutral tracks.  (What is envisioned by the vector of particle sets?)  In the case that multiple particle sets (vertices) are useful and or necessary, is it helpful to replicate the DNeutralTrack objects at every vertex?  Note that calculation of tprojected or FOM is almost instantaneous for neutrals.

Finally, at the bottom of your page, the PseudoCode.cc file requires a Hall B password that I don't know.

Overall, I think this is an excellent step in the right direction.  We want this high level information to be easily accessible in some uniform format.  I think the goal is to come up with the simplest possible structure that still maintains all the functionality that is needed.

-Matt




On Jun 20, 2011, at 3:37 PM, Paul Mattione wrote:

> I think that the current class structure has become a little  
> fragmented at the top level, and I'd like to suggest a few changes to  
> make things simpler and more intuitive.  In addition to DChargedTrack  
> and DPhoton no longer being used to create the DPhysicsEvent class,  
> the reconstruction algorithm assumes that every calorimeter shower  
> comes from either a charged particle or a photon, excluding neutrons  
> (such as from Lambda decay).
> 
> Here's a link to an overview of the current top-level class structure,  
> and a proposal for a new (slightly different) class structure that I'm  
> working on:
> 
> http://www.jlab.org/Hall-D/software/wiki/index.php/Mattione_Particle_Classes
> 
> The next offline meeting is over a week away, but in the meantime I  
> would appreciate it if you guys could let me know what you think.   
> Thanks!
> 
>  - Paul Mattione
> 
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