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icon4.gif  New pbarpSystem and pbardSystem implementations [message #13193] Tue, 13 March 2012 16:10 Go to next message
StefanoSpataro is currently offline  StefanoSpataro
Messages: 2736
Registered: June 2005
Location: Torino
first-grade participant

From: *to.infn.it
Dear all,
few new implementations were done in EvtGen.

First all now, now you can set the spin of the initial pbar-p system, by using:
pbarpSystem0
pbarpSystem1
pbarpSystem2

The old pbarpSystem remains at the usual place, but please remember that it has spin 1 so you cannot use it with other models (i.e. the SVV used for eta_c).

Another note: if you use as initial state a particle, i.e. eta_c, in generation you will have an invariant mass resolution due to the particle width, and not to the beam momentum spread. For this reason we suggest to use pbarpSystem as initial state.


Morevoer, thanks to Albrecht we have a new model to simulate collisions antiproton-deuteron. In this case you have to use "pbardSystem" as initial state, and write a DEC file such as:

noPhotos
#
Decay pbardSystem
  1.0   p+  pbarnSystem		DeuteronSpectator 1.0 1.16;
Enddecay
#
Decay pbarnSystem
  1.0   pi- phi			PHSP;
Enddecay 
#
Decay phi
  1.0   K+ K-			VSS;
Enddecay
#
End


Maybe Albrecht could comment about the parameters to provide to the DeuteronSpectator model.
Re: New pbarpSystem and pbardSystem implementations [message #13196 is a reply to message #13193] Tue, 13 March 2012 17:16 Go to previous messageGo to next message
Albrecht Gillitzer is currently offline  Albrecht Gillitzer
Messages: 49
Registered: March 2004
continuous participant
From: *ikp.kfa-juelich.de
Hi,

Let me add some remarks concerning the pbar+d decay model:
It is based on one on-shell nucleon in the deuteron target not participating in the reaction (= the "spectator") while the other nucleon is off-shell to respect 4-momentum balance. The momentum distribution is parametrized with a Hulthen function.
Usually the struck (off-shell) nucleon is the neutron while the proton is the spectator (otherwise one would prefer a free proton target). However the decay model should also work for the latter case if the decay file is written accordingly.

As Stefano mentioned, there are two parameters in usage of the decay model:
Decay pbardSystem
1.0 p+ pbarnSystem DeuteronSpectator 1.0 1.16;
Enddecay
1st parameter: maximum internal momentum in the deuteron in GeV/c
2nd parameter: minimum mass of the residual pbar+n system for the specified decay (in this case M_phi+M_Pi-).

I plan to give a more detailed explanation in the next CM.

Albrecht
Re: New pbarpSystem and pbardSystem implementations [message #14195 is a reply to message #13193] Thu, 08 November 2012 11:28 Go to previous messageGo to next message
donghee is currently offline  donghee
Messages: 385
Registered: January 2009
Location: Germnay
first-grade participant
From: *kph.uni-mainz.de
Dear all,

I want to use pbarpSystem1 producing a vector particle.
My decay file "MyDecay.dec" introduce

Quote:


noPhotos
#
Decay pbarpSystem1
1.0 D+ D- VSS;
Enddecay
#
Decay D-
1.0 K+ pi- pi- D_DALITZ;
Enddecay
#
Decay D+
1.0 K- pi+ pi+ D_DALITZ;
Enddecay
#
End



And simulation macro
Quote:


PndEvtGenDirect *evtGen = new PndEvtGenDirect("pbarpSystem1", "MyDecay.dec");



But it is not recognized at EvtGen...here is error message of PANDAroot.
Quote:


EvtGen:Unknown particle name:pbarpSystem1 on line 4




How can I use pbarpSystem1 in simulation?

Thanks.
Re: New pbarpSystem and pbardSystem implementations [message #14196 is a reply to message #14195] Thu, 08 November 2012 11:37 Go to previous messageGo to next message
StefanoSpataro is currently offline  StefanoSpataro
Messages: 2736
Registered: June 2005
Location: Torino
first-grade participant

From: *to.infn.it
Do you have the correct evt.pdl? Check there if your pbarpSystem1 is defined.
Re: New pbarpSystem and pbardSystem implementations [message #14197 is a reply to message #13193] Thu, 08 November 2012 14:56 Go to previous message
donghee is currently offline  donghee
Messages: 385
Registered: January 2009
Location: Germnay
first-grade participant
From: *kph.uni-mainz.de
Dear Stefano,

I used my own evt.pdl, after copy pbarpSystem0,1,2 into evt.pdl, works fine.

Thank you!
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