[Halld-offline] retrieving information on generated particles

[Mark M. Ito]

Kei,

Thanks for that note.

On the agenda it goes....

   -- Mark

On 09/10/2013 08:25 AM, Kei Moriya wrote:
>
> Hi Mark and offliners,
>
> Regarding the talk I gave yesterday at the physics meeting,
> I think obtaining the generated particle information
> is a relatively high-priority issue since this affects
> every analysis where we want to know the main
> background channels.
>
> I therefore propose that this be put on the agenda
> for offline issues, and make a collaborative effort
> to solve it, or at least have a plan of what to do
> in the coming weeks.
>
> I think there are many inter-related issues:
> 1. We need to maintain a consistent output throughout
> the processing flow from pythia/hdgeant/REST/Paul's trees,
> which probably all have different experts.
> 2. The upgrade to GEANT4 in the coming weeks. We don't want
> to duplicate the same efforts for different code.
> 3. There needs to be agreement on which information needs
> to be saved and decide which PID scheme to use.
>
> I think part of the confusion comes from the PID scheme,
> since pythia uses the PDG PID scheme internally, while
> the GlueX PID scheme depends on the GEANT particle scheme,
> but has been modified for numbers higher than 45. Sometimes
> the conversion between different schemes seems to work,
> sometimes they don't.
>
> I think we should try to:
> 1. see which problems can be fixed rather easily for GEANT3
> 2. be aware that the problem currently exists while updating to GEANT4
>
> I can try to iron out some of the specific issues with Paul
> and others by the next offline meeting next week, but if anybody has any
> other input or suggestions, I think it would benefit the discussion.
>
> Below is part of an email I got from Paul, and I agree with
> what he has here. One more thing I would like is a mechanism
> that tells me what created the particle. As Curtis
> mentioned during the meeting, retaining wide states such as
> rho mesons would be controversial, but I think we should aim
> for something that works for the majority of analyses at this stage,
> even if it means sweeping generalizations.
>
> ---
>
> It seems like, beyond bug fixes, the best long-term solution for 
> getting the thrown topology in ROOT is function(s) that will return 
> you either:
>
> 1) A string of the particles
> 2) A vector of the particle IDs
> 3) A map of particle_id to #-of-particles
>
> These functions would have options like:
>
> 1) Include final-state particles only.
> 2) Include long-lived-decaying (LLD) (e.g. Lambda) particles and 
> final-state particles, excluding final-state particles that decayed 
> from LLD particles.
> 3) Include all "known" decaying particles (e.g. rho resonances, 
> exclude diquarks), excluding final-state particles that decayed from 
> known-decaying particles.
>
> ---
>
> Thanks,
>     Kei

-- 
Mark M. Ito, Jefferson Lab, (757)269-5295, marki at jlab.org