Dave Gerdes wrote: "I am a bit confused by the difference between a
Particle and a MCParticle and the fact that they have different status
codes".
The Particle class is part of the hep.physics package and is designed to
represent a generator level particle as read in from a StdHEP file.
The MCParticle class is part of the hep.lcd.event package extends
Particle to provide a place to store additional information generated by
Gismo as particles are swum through the detector. Specifically it
provides the point where the particle enters the Calorimeter and the
Gismo Status (returned by getStatus(), not to be confused with the
StdHEP status returned by getStatusCode()).
Things are not quite as neat as the should be for several reasons.
1) The Gismo Status returned by getStatus() is somewhat bizarre and
hard to understand.
2) The original StdHEP status code is lost as the particles are fed
through Gismo, and has to be "guessed" based on the Gismo Status code.
This is done by mapping the each Gismo Status into one of INTERMEDIATE
or FINALSTATE.
3) The same particle may appear multiple times in the Gismo output,
and may have the same gismoStatus code each time, making the mapping in
2 impossible to perform accurately
4) Gismo arbitrarily truncates the MC particle list at a depth of 10
particles, so unstable particles may appear with no daughters.
5) The MC generators themselves often produce extra initial state and
intermediate state "bookkeeping" particles that can further confuse
people trying to understand the MC particle heirarchy.
Hopefully some of these problems can be fixed in a future release of the
LCD Gismo code.
Tony
-----Original Message-----
From: David Gerdes [mailto:[log in to unmask]]
Sent: Wednesday, April 07, 1999 4:39 PM
To: [log in to unmask]; [log in to unmask]
Cc: David Gerdes
Subject: Hits to partons
Hi,
I am writing some code to associate final state objects (calorimeter or
tracking hits, e.g.) with partons from the underlying process (i.e. one
of the 6 final-state partons from a ttbar decay). I'd appreciate your
suggestions for the best way to proceed. I have working code that
returns
an Enumeration of the 6 ttbar partons. Is it a legit approach to trace
the contributing MCParticles back by successive getParent() calls until
I either reach one of the top partons or run out of parents? I am a bit
confused by the difference between a Particle and a MCParticle and the
fact that they have different status codes.
Regards,
Dave
--------------------------------------
David Gerdes, University of Michigan
(734) 647-3807 / (734) 936-1817 FAX
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http://umaxp1.physics.lsa.umich.edu/~gerdes/
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