Evtgen - prob>probmax [message #12371] |
Wed, 27 July 2011 15:45 ![Go to next message Go to next message](/theme/gsi/images/down.png) |
Tobias Weber
Messages: 9 Registered: November 2010
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occasional visitor |
From: *kph.uni-mainz.de
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Hi,
For my ppbar->X(3872)->J/Psi pi+pi- I want to use some decay models from EvtGen. In order to do this I added the following line to evt.pdl
add p Meson X3872 59 3.872 0.0001 1.0 0 2 0 0
and made some changes to my decay file. When I now run a simulation I get lines like these from the monte carlo.
EvtGen:prob > probmax:(0.11882>0.08)(VVPIPI) X3872 -> J/psi pi+ pi-
But all events seem to be propageted by Geant.
Could someone tell me what this warning means and what I am doing wrong.
Cheers,
Tobias
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Re: Evtgen - prob>probmax [message #13562 is a reply to message #13560] |
Sat, 02 June 2012 11:32 ![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) |
StefanoSpataro
Messages: 2736 Registered: June 2005 Location: Torino
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first-grade participant |
![theavatar_ss](/theme/gsi/images/skype.png) From: *30-79-r.retail.telecomitalia.it
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Hi,
inside Panda we don't have such knowledge about EvtGen, the question should be asked directly to EvtGen developers.
Meanwhile, I can give you my personal idea about. There are some models where the cross section has some divergence, i.e. rutherford cross section. In order to avoid such divergence, you put in EvtGen model a a cut on maximum probability. If the random prob value is higher, then the event is discarded... more or less the same things which happens to dpm when you set the minimum theta angle. In phase space this message never appears because you don't set this probmax value. Then, if i were in you, I should not be worried about if they are not very frequent, it is only a warning from the model itself and you did nothing wrong.
A more detailed answer can be found only reading EvtGen documentation/code or asking to the authors.
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Re: Evtgen - prob>probmax [message #13581 is a reply to message #13579] |
Thu, 07 June 2012 14:24 ![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) |
MartinJGaluska
Messages: 203 Registered: March 2010 Location: Germany
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first-grade participant |
From: *physik.uni-giessen.de
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I have simulated 10 000 events each of \psi(2S) -> J/\psi \pi^+ \pi^- with PndEvtGenDirect and here are the counts of the "prob > probmax" warnings I get:
mass of psi(2S) & VVPiPi ProbMax & # of "prob > probmax" messages
3.872 GeV & new code & 0
3.872 GeV & old code & 6111
3.68596 GeV & new code & 0
3.68596 GeV & old code & 0
(Sorry, I don't know how to properly format this.)
To sum up:
With the old code (hard-coded value of 0.08 for ProbMax in VVPiPi) I get no warnings for the psi(2S) having its regular mass of 3.68596 GeV. I also do not get any warnings with the code that I have written.
When I change the psi(2S) mass to 3.872 GeV, I get warnings in 6111 out of 10 000 events with the old code. All warnings disappear with the new code.
As an aside: I also tried to just hard-code a higher value for ProbMax (I chose 0.8) and when I ran the simulations, all warnings disappeared as well. However, I am not sure of the effect this value might have on the output of EvtGen. I am still waiting for my email to be answered by the Warwick group.
[Updated on: Thu, 07 June 2012 14:24] Report message to a moderator
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Re: Evtgen - prob>probmax [message #13590 is a reply to message #13581] |
Mon, 11 June 2012 12:25 ![Go to previous message Go to previous message](/theme/gsi/images/up.png) |
MartinJGaluska
Messages: 203 Registered: March 2010 Location: Germany
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first-grade participant |
From: *physik.uni-giessen.de
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I have just received an answer to my Email that I sent to the Warwick team. They believe that the VVPiPi decay model should work fine with the changes. However, they will evaluate if they find a method for setting the ProbMax value which is general enough to apply to other decay models as well.
Quote: |
Dear Martin.
Thanks for this information, we will cross-check and see whether this is best option to proceed or whether we find better way. One of the issues is that proper setting of maximum probability is not bound to VVPIPI model, but it appears on many other places, so we want to look for solution which is general and and solid for all models.
What you did for now should be fine for your purposes (as long as you do not get error message again).
Regards,
Michal
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