Lambda Lambdabar simulations [message #16309] |
Tue, 15 April 2014 12:10 ![Go to next message Go to next message](/theme/gsi/images/down.png) |
Karin Schönning
Messages: 65 Registered: August 2012 Location: Uppsala University
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continuous participant |
From: *physics.uu.se
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Yesterday's meeting (which I regret I could not follow to the end) triggered some discussion on the Lambda Lambdabar channel and in particular the acceptance in the forward direction. Donghee has suggested it may be improved if the requirement of all four final state particles being reconstructed in the final state. This is probably true but I don't think this is the reason for the discrepancy with the physics book results (or the thesis of Sohie Grape where the details are given). Sophie required all final state particles (but no paricle ID), vertex fit of both Lambda and Lambdabar, mass cuts of the same and also a tree fit for pbar p -> Lambdabar Lambda. On the other hand, pandaroot was not used for these results but only the old, BABAR based framework. It is of course much less realistic but I would be surprised if it causes something as significant as the forward acceptance. I am also looking into the Lambdabar Lambda channel now and will check if I reproduce Donghee's findings.
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Re: Lambda Lambdabar simulations [message #16320 is a reply to message #16319] |
Tue, 15 April 2014 15:27 ![Go to previous message Go to previous message](/theme/gsi/images/up.png) ![Go to next message Go to next message](/theme/gsi/images/down.png) |
Karin Schönning
Messages: 65 Registered: August 2012 Location: Uppsala University
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continuous participant |
From: *physics.uu.se
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The distance between production and decay vertex for Lambda look about the same in the fast and the full simulations, so I think it is properly treated also in the former.
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Re: Lambda Lambdabar simulations [message #16334 is a reply to message #16319] |
Wed, 16 April 2014 11:00 ![Go to previous message Go to previous message](/theme/gsi/images/up.png) ![Go to next message Go to next message](/theme/gsi/images/down.png) |
donghee
Messages: 385 Registered: January 2009 Location: Germnay
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first-grade participant |
From: *kph.uni-mainz.de
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Hi Bertram,
Quote:
How are such long living particles treated in the fast simulation?
In full simulation, we could not handle correctly V0 decay, because of no V0 track reconstruction at this moment as it is well known.
Therefore acceptance for lambda and lambdabar is quite poor and roughly below 20% without any PID application.
In the fast simulation, the situation seems to be same. If lambda and lambdabar has a long distance life time, then we do not chance to reconstruct those track in the fast simulation, too.
Quote:
For the Physics Book studies we therefore defined the lambda as a stable particle in the event generator. The decay has been considered afterwards in the GEANT simulation.
Your comment about stable mode in EvtGen is very interesting for me, You mean that we can also use stable mode in EvtGen generator.
I know the stable mode for lambda or K_s in DPM, but I have never heard such handling in EvtGen.
Presently in my EvtGen generator frame, lambda-lambdabar has been produced and allow directly charged decay mode(to proton and pion).
Then all final state particles are transfered to the GEANT.
Could you tell me about difference between you and my approach?
Best wishes,
Donghee
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