The problems you are having are directly related to the way the
generator fills the HepEvt common block. The parent/daughter
relationships returned by the JAS classes for StdHep events directly
reflect the info returned by the generator. I have dumped the
parent/daughter structure from a typical tt bar event below.
Some observations:
1) The initial state e+e- are listed as having no daughters and no
parents
2) The parent-daughter relationship is non-intuitive, just becase B is
A's daughter doesnt imply that A is B's parent (according to the
generator).
3) Some particles (e.g the type 92 "string") have multiple parents.
The only subtlety the JAS introduces in to the process is that there is
both a getParent() and getParents() method in the Particle class. The
getParent method works only in the case that the particle has a single
parent (currently it returns null if there is either 0 parents, or >1
parent, in future it will throw an exception if there is >1 parent).
getParents works in all cases, although its a little harder to use since
it returns an enumeration which you have to loop over.
In conclusion I think you can probably solve both the "work up" and
"work down" cases by:
1) For work down, loop over the particles until you find the first
non-electron and start from there.
2) For work up, use getParents rather than getParent
I havent actually tested either of these but I think they should work.
Tony
Event 0
id=11 parents=0-0 daughters=0-0
id=-11 parents=0-0 daughters=0-0
id=11 parents=1-0 daughters=0-0
id=-11 parents=2-0 daughters=0-0
id=11 parents=3-0 daughters=0-0
id=-11 parents=4-0 daughters=0-0
id=23 parents=5-6 daughters=0-0
id=6 parents=7-0 daughters=0-0
id=-6 parents=7-0 daughters=0-0
id=24 parents=8-0 daughters=0-0
id=5 parents=8-0 daughters=0-0
id=-24 parents=9-0 daughters=0-0
id=-5 parents=9-0 daughters=0-0
id=-11 parents=10-0 daughters=0-0
id=12 parents=10-0 daughters=0-0
id=3 parents=12-0 daughters=0-0
id=-4 parents=12-0 daughters=0-0
id=23 parents=7-0 daughters=0-0
id=24 parents=10-0 daughters=21-22
id=-24 parents=12-0 daughters=29-40
id=-11 parents=14-0 daughters=0-0
id=12 parents=15-0 daughters=0-0
id=5 parents=11-0 daughters=41-41
id=21 parents=11-0 daughters=41-41
id=21 parents=11-0 daughters=41-41
id=21 parents=13-0 daughters=41-41
id=21 parents=13-0 daughters=41-41
id=-5 parents=13-0 daughters=41-41
id=-4 parents=17-0 daughters=55-55
id=21 parents=17-0 daughters=55-55
id=21 parents=17-0 daughters=55-55
id=21 parents=16-0 daughters=55-55
id=21 parents=16-0 daughters=55-55
id=21 parents=16-0 daughters=55-55
id=21 parents=16-0 daughters=55-55
id=21 parents=16-0 daughters=55-55
id=21 parents=16-0 daughters=55-55
id=21 parents=16-0 daughters=55-55
id=21 parents=16-0 daughters=55-55
id=3 parents=16-0 daughters=55-55
id=92 parents=23-28 daughters=42-54
id=-523 parents=41-0 daughters=74-75
id=211 parents=41-0 daughters=0-0
id=313 parents=41-0 daughters=76-77
id=-321 parents=41-0 daughters=0-0
id=213 parents=41-0 daughters=78-79
id=-213 parents=41-0 daughters=80-81
id=2112 parents=41-0 daughters=0-0
id=-2114 parents=41-0 daughters=82-83
id=321 parents=41-0 daughters=0-0
id=-323 parents=41-0 daughters=84-85
id=213 parents=41-0 daughters=86-87
id=-213 parents=41-0 daughters=88-89
id=523 parents=41-0 daughters=90-91
id=92 parents=29-40 daughters=56-73
id=-413 parents=55-0 daughters=92-93
id=111 parents=55-0 daughters=94-95
id=211 parents=55-0 daughters=0-0
id=-323 parents=55-0 daughters=96-97
id=313 parents=55-0 daughters=98-99
id=113 parents=55-0 daughters=100-101
id=113 parents=55-0 daughters=102-103
id=211 parents=55-0 daughters=0-0
id=111 parents=55-0 daughters=104-105
id=-211 parents=55-0 daughters=0-0
id=221 parents=55-0 daughters=106-107
id=211 parents=55-0 daughters=0-0
id=223 parents=55-0 daughters=108-110
id=-211 parents=55-0 daughters=0-0
id=223 parents=55-0 daughters=111-113
id=213 parents=55-0 daughters=114-115
id=-213 parents=55-0 daughters=116-117
id=-311 parents=55-0 daughters=118-118
id=-521 parents=42-0 daughters=119-121
id=22 parents=42-0 daughters=0-0
id=311 parents=44-0 daughters=122-122
id=111 parents=44-0 daughters=123-124
id=211 parents=46-0 daughters=0-0
id=111 parents=46-0 daughters=125-126
id=-211 parents=47-0 daughters=0-0
id=111 parents=47-0 daughters=127-128
id=-2112 parents=49-0 daughters=0-0
id=111 parents=49-0 daughters=129-130
id=-311 parents=51-0 daughters=131-131
id=-211 parents=51-0 daughters=0-0
id=211 parents=52-0 daughters=0-0
id=111 parents=52-0 daughters=132-133
id=-211 parents=53-0 daughters=0-0
id=111 parents=53-0 daughters=134-135
id=521 parents=54-0 daughters=136-138
id=22 parents=54-0 daughters=0-0
id=-411 parents=56-0 daughters=139-140
id=111 parents=56-0 daughters=141-142
id=22 parents=57-0 daughters=0-0
id=22 parents=57-0 daughters=0-0
id=-311 parents=59-0 daughters=143-143
id=-211 parents=59-0 daughters=0-0
id=321 parents=60-0 daughters=0-0
id=-211 parents=60-0 daughters=0-0
id=-211 parents=61-0 daughters=0-0
id=211 parents=61-0 daughters=0-0
id=211 parents=62-0 daughters=0-0
id=-211 parents=62-0 daughters=0-0
id=22 parents=64-0 daughters=0-0
id=22 parents=64-0 daughters=0-0
id=22 parents=66-0 daughters=0-0
id=22 parents=66-0 daughters=0-0
id=-211 parents=68-0 daughters=0-0
id=211 parents=68-0 daughters=0-0
id=111 parents=68-0 daughters=144-145
id=-211 parents=70-0 daughters=0-0
id=211 parents=70-0 daughters=0-0
id=111 parents=70-0 daughters=146-147
id=211 parents=71-0 daughters=0-0
id=111 parents=71-0 daughters=148-149
id=-211 parents=72-0 daughters=0-0
id=111 parents=72-0 daughters=150-151
id=310 parents=73-0 daughters=152-153
id=423 parents=74-0 daughters=154-155
id=-211 parents=74-0 daughters=0-0
id=221 parents=74-0 daughters=156-158
id=310 parents=76-0 daughters=159-160
id=22 parents=77-0 daughters=0-0
id=22 parents=77-0 daughters=0-0
id=22 parents=79-0 daughters=0-0
id=22 parents=79-0 daughters=0-0
id=22 parents=81-0 daughters=0-0
id=22 parents=81-0 daughters=0-0
id=22 parents=83-0 daughters=0-0
id=22 parents=83-0 daughters=0-0
id=310 parents=84-0 daughters=161-162
id=22 parents=87-0 daughters=0-0
id=22 parents=87-0 daughters=0-0
id=22 parents=89-0 daughters=0-0
id=22 parents=89-0 daughters=0-0
id=-423 parents=90-0 daughters=163-164
id=211 parents=90-0 daughters=0-0
id=111 parents=90-0 daughters=165-166
id=311 parents=92-0 daughters=167-167
id=-20213 parents=92-0 daughters=168-169
id=22 parents=93-0 daughters=0-0
id=22 parents=93-0 daughters=0-0
id=310 parents=96-0 daughters=170-171
id=22 parents=110-0 daughters=0-0
id=22 parents=110-0 daughters=0-0
id=22 parents=113-0 daughters=0-0
id=22 parents=113-0 daughters=0-0
id=22 parents=115-0 daughters=0-0
id=22 parents=115-0 daughters=0-0
id=22 parents=117-0 daughters=0-0
id=22 parents=117-0 daughters=0-0
id=-211 parents=118-0 daughters=0-0
id=211 parents=118-0 daughters=0-0
id=421 parents=119-0 daughters=172-173
id=22 parents=119-0 daughters=0-0
id=111 parents=121-0 daughters=174-176
id=111 parents=121-0 daughters=177-178
id=111 parents=121-0 daughters=179-180
id=211 parents=122-0 daughters=0-0
id=-211 parents=122-0 daughters=0-0
id=111 parents=131-0 daughters=181-182
id=111 parents=131-0 daughters=183-184
id=-421 parents=136-0 daughters=185-189
id=111 parents=136-0 daughters=190-191
id=22 parents=138-0 daughters=0-0
id=22 parents=138-0 daughters=0-0
id=310 parents=139-0 daughters=192-193
id=113 parents=140-0 daughters=194-195
id=-211 parents=140-0 daughters=0-0
id=-211 parents=143-0 daughters=0-0
id=211 parents=143-0 daughters=0-0
id=-323 parents=154-0 daughters=196-197
id=211 parents=154-0 daughters=0-0
id=22 parents=156-0 daughters=0-0
id=-11 parents=156-0 daughters=0-0
id=11 parents=156-0 daughters=0-0
id=22 parents=157-0 daughters=0-0
id=22 parents=157-0 daughters=0-0
id=22 parents=158-0 daughters=0-0
id=22 parents=158-0 daughters=0-0
id=22 parents=161-0 daughters=0-0
id=22 parents=161-0 daughters=0-0
id=22 parents=162-0 daughters=0-0
id=22 parents=162-0 daughters=0-0
id=321 parents=163-0 daughters=0-0
id=-211 parents=163-0 daughters=0-0
id=-211 parents=163-0 daughters=0-0
id=211 parents=163-0 daughters=0-0
id=111 parents=163-0 daughters=198-199
id=22 parents=164-0 daughters=0-0
id=22 parents=164-0 daughters=0-0
id=211 parents=167-0 daughters=0-0
id=-211 parents=167-0 daughters=0-0
id=-211 parents=168-0 daughters=0-0
id=211 parents=168-0 daughters=0-0
id=-321 parents=172-0 daughters=0-0
id=111 parents=172-0 daughters=200-201
id=22 parents=189-0 daughters=0-0
id=22 parents=189-0 daughters=0-0
id=22 parents=197-0 daughters=0-0
id=22 parents=197-0 daughters=0-0
id=22 parents=0-0 daughters=0-0
id=22 parents=0-0 daughters=0-0
> -----Original Message-----
> From: Mahalaxmi Krishnamurthy [mailto:[log in to unmask]]
> Sent: Thursday, April 22, 1999 11:47 AM
> To: [log in to unmask]
> Cc: Robert Wilson
> Subject: Getting complete hierarchy
>
>
>
> HI ,
>
> Our goal is to associate final state particles with
> initial partons. To do
> this with highest statistics we want to use StdHEP event
> generator datasets
> (generated by Gray at SLAC?). We are using JAS to read them.
>
> Problem: The Particle.getParent() chain going up
> terminates at "unknown" (
> id=92, probably the fragmentation string?) .
> Particle.getDaughters() on the
> initial partons is empty, so one cannot go in the other direction.
>
> Oddly enough, in the lcd-sim files one can follow the
> daughters chain down
> through the "Idontknowino" e.g. t->Wb->, W->ud->
> Idontknowino->physical
> particles; and the tbar down through to its own
> Idontknowino. This allows us
> to associate final state particles with initial partons.
>
> Does anyone know how to get the information we need
> (i.e. the complete
> production/decay hierarchy) from stdhep files using JAS.
>
>
>
> Maha, Bob.
>
>
>
>
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