| pbarpSystem [message #15094] |
Mon, 05 August 2013 12:47  |
Simon Reiter
Messages: 44
Registered: May 2013
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continuous participant |
From: *zeu.uni-giessen.de
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Hi all,
I was wondering why the mass of the pbarpSystem in evt.pdl is set to 2.98 GeV. How is this calculated and is this used in the simulation macro?
And why does it has a width of 0.1 GeV?
Additionally, please change the description in evt.pdl for the spin. It's J (total angular momentum quantum number) not S (spin)! It is just confusing..
Best regards,
Simon
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| Re: pbarpSystem [message #15106 is a reply to message #15100] |
Mon, 05 August 2013 16:48  |
Jens Sören Lange
Messages: 193
Registered: June 2005
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first-grade participant |
From: *wlan.uni-giessen.de
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Hi Stefano, I disagree.
I think the user should actually not be discouraged to change evt.pdl.
1.) Our evt.pdl is hopelessly out of date, many masses and widths are wrong (it means different from PDG).
2.) The default width of the pbarsystem 0.1 GeV is definitely wrong (should be zero) and if we are not mistaken, it is probably not initialized by EvtGen with a "reasonable value". At least I see different results if you keep the default or you put in zero width "by hand" in the evt.pdl.
The default pbarpsystem mass of 2.98 GeV is maybe the eta_c mass. As Klaus says, it is overwritten when EvtGen starts, but you see what happened here: somebody put in whatever value into evt.pdl and then checked it into svn.
3.) modifying evt.pdl is still the best way to introduce a new particle.
So, I think, if you want to show any PandaRoot result on a conference (we want to show on the CHARM'13 in 3 weeks from now), we have to check and maybe modify the evt.pdl.
cheers, Soeren
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| Re: pbarpSystem [message #15107 is a reply to message #15106] |
Mon, 05 August 2013 19:09 |
StefanoSpataro
Messages: 2736
Registered: June 2005
Location: Torino
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first-grade participant |
From: 2.235.190*
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Hi Soeren,
I was not clear, ok, I admit it.
I think it makes no sense to change from our side "spin" into "J", this is just semantics. The evt.pdl style, definition and header" come from EvtGen, maybe one could raise the question to the developers (I mean the Warwick team).
With the new EvtGen we have an updated evt.pdl (check EvtGenNew/EvtGen/Private). If we start to modify the definitions of the particles "randomly", this could be risky. Of course one can use the evt.pdl that he wants.
The basic idea should be that particle properties are modified inside the dec file, and not in the common evt.pdl, which is the standard for all the users and analyses.
About pbarpSystem definition, this is what was used for the physics book. I believe it was hardly checked, but it would be good if somebody could check again if the results are changed by modifying its properties.
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| Re: pbarpSystem [message #15114 is a reply to message #15109] |
Wed, 07 August 2013 00:21 |
Elisabetta Prencipe (2)
Messages: 214
Registered: February 2013
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first-grade participant |
From: *web.vodafone.de
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Hi Simon,
to simulate a new particle with EvtGen you can use the particles listed as 'dummiesXX' in the file evt.pdl. For instance, let's assume that you want to simulate a particle called Y, with mass = A, width = B, spin and charge set up to 0 (remember to pass the values of mass a width in [GeV]). Then you need to do the following in your file.dec:
###########################
Particle dummy00_1 A B
ChangeMassMin dummy00_1 [min-mass-value]
ChangeMassMax dummy00_1 [max-mass-value]
#
Alias MyY dummy00_1
Decay MyY
1.0 [daughter-one] [daughter-two] [daughte-whatever] [model]
Enddecay
Indeed, if you need to simulate a new particle of spin 1 and charge =0, then you need to use 'dummy01_1' in your file.dec; you can find the list of all dummy particles available in the file evt.pdl. By default, the dummy00_1 gives you a LundID = 51.
I hope it helps, Elisabetta
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| Re: pbarpSystem [message #15127 is a reply to message #15126] |
Wed, 07 August 2013 16:48 |
Elisabetta Prencipe (2)
Messages: 214
Registered: February 2013
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first-grade participant |
From: *ikp.kfa-juelich.de
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Hi Simon,
to set up both value to 0 is not correct, as EvtGen is written in a way that a mass interval should be passed somewhere. Now, you can choose those limits your own, or you can accept the default value of Delta Mass of the dummyXX in evt.pdl; but it must be written somewhere. So, if you comment those 2 lines you accept the default setting in evt.pdl, and this should be fine.
When I generated my new particle, I set up the value depending on the limit of the PHSP distribution of the daughters of my new particle, and it worked out. I never tried without any Delta mass value.
Just one comment: you can decide in this way to set up the particle properties (not only the ones related to the dummy particles, but also for instance for the D0, Ks, Lambda..) from your file.dec, without modifying evt.pdl. You can redefine for the particle of the evt.pdl list the mass, width, Lund-ID,....this is still fine.
Dummy00_1, for instance, by default is just a particle with mass = 1 GeV/c^2, width = 0.1, LundID= 51, spin =0 and charge =0. No additional properties. From your file.dec you are able to redefine the mass and the width, as from the example I had sent you, and you accept by default the other properties of this dummy00_1 particle (spin, charge). Make sure in the simulation macro to set up properly the momentum value, depending on the mass of your new particle, and the name of the Resonant state, wherever it is called in the macro. You are now using a particle calle "dummyXX_Y", whatever it is in your case.
Elisabetta
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