[Halld-offline] [Fwd: Re: bggen thrown particle type]

[David Lawrence]

Hi Eugene and Blake,

    Yes, Eugene is correct. Setting the geantid to zero flags hdgeant to 
ignore the particle. That allows intermediate particles to be stored 
along with final state ones.

Regards,
-David

Blake Leverington wrote:
>
>
> ------------------------------------------------------------------------
>
> Subject:
> Re: bggen thrown particle type
> From:
> Blake Leverington <leverinb at uregina.ca>
> Date:
> Mon, 27 Jul 2009 19:54:34 -0600
> To:
> Eugene Chudakov <gen at jlab.org>
>
> To:
> Eugene Chudakov <gen at jlab.org>
> CC:
> Alexander Somov <somov at jlab.org>
>
>
> Ok, I was unsure how HDGeant handled the events that weren't final 
> state. I was trying to figure out what my background was and all these 
> extra events were confusing me.
>
> -Blake
>
> Eugene Chudakov wrote:
>> The bggen writes out everything, since it might be
>> useful to be able to check the event structure later. The reading
>> routine in HDGeant should be smart and store into GEANT only the entries
>> with a non-zero code. I thought it had been done this way, but
>> I am not sure. Alex Somov or David may know. Alex used the bggen
>> output with HDGeant.
>>
>> Eugene
>>
>>
>> On Mon, 27 Jul 2009, Blake Leverington wrote:
>>
>>> Hi Eugene,
>>>
>>> I think I've discovered the problem. When writing out the bggen process
>>> to the hddm file, it was writing out ALL the events in the process tree
>>> instead of only the final state events.
>>>
>>> line 126 of bg_hddm.c should have a piece of code :
>>> if (keve[i].mech != 1 || keve[i].geantid == 0) continue;
>>>
>>> "keve[i].mech != 1" requires that the particle must be a final state
>>> particle and "keve[i].geantid == 0" requires that is also not be a 
>>> process.
>>>
>>> Let me know if this isn't right or you think it should be different.
>>> -Blake
>>>
>>>
>>> Blake Leverington wrote:
>>>> Hi Eugene,
>>>>
>>>> When I look at the particle type for particle thrown particle from 
>>>> bggen, I notice a lot of TYPE 0, which in GEANT doesn't mean 
>>>> anything. In PYTHIA, this means a process. I also noticed something 
>>>> funny in the multiplicity. Looking at the number of particles, the 
>>>> mean number is in the 20s, where when I look at the output of 
>>>> displayed events from bggen, it looks more like 6-9 final state 
>>>> particles, and 20 or so particles in the Whole Process Tree.
>>>>
>>>> Is there a flag or something I'm not calling to only output final 
>>>> state particles?
>>>>
>>>> -Blake
>>>>
>>>
>>>
>>
>
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 David Lawrence Ph.D.
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