| eta_c generation with EvtGen [message #12839] |
Thu, 01 December 2011 12:44  |
Dima Melnychuk
Messages: 213
Registered: April 2004
Location: National Centre for Nucle...
|
first-grade participant |
From: *fuw.edu.pl
|
|
Dear all,
I found one conceptual problem with eta_c event generation which was due to my misunderstanding of EvtGen event generator.
Namely in eta_c produced in p+pbar in formation experiment scan will be performed at several energies around resonance and what it does make sense to study for tracking TDR is one momentum point corresponding to resonance maximum. And here a shape of eta_c resonance should not be considered at all. At least it is my understanding and in this way the studies were done for example for physics book.
But producing eta_c with
PndEvtGenDirect *EvtGen = new PndEvtGenDirect("etac","EtaCInclusive_2phi.dec");
eta_c was taken on different positions of resonance.
Here PndEvtGenDirect behave a little bit strange, namely for one run or one seed of random number generator it takes one fixed mass. And when I generated 1000 eta_c locally with one seed I had as a result for efficiency which was different from efficiency obtained on grid, and as Stefano observed last time eta_c width for 1000 events was 2 times smaller than on grid because it was for one fixed point, whereas on the grid it was averaged over resonance shape.
So I updated run_sim_stt_evt.C for
PndEvtGenDirect *EvtGen = new PndEvtGenDirect("pbarpSystem","EtaCInclusive_2phi.dec",3.6772);
and in decay file EtaCInclusive_2phi.dec
I replaced etac for pbarpSystem
So at least it's my understanding how it should be done.
So event generation how it was done y now was not incorrect but it was not I supposed its was.
Particularly applying 4C-fit makes sense for fixed pbar momentum for each point of resonance scan.
So, any opinion?
And if there are no objections I would like to ask Stefano to generate once again data on grid.
It will require update of run_sim_stt_evt.C and EtaCInclusive_2phi.dec and in principle do not require update of pandaroot on grid (but will require modification of script for data production).
Situation is the same for psi(3770) but this problem is NOT related to multipion channel.
Best regards,
Dima
|
|
|
|
|
|
|
|
| Re: eta_c generation with EvtGen [message #12843 is a reply to message #12842] |
Fri, 02 December 2011 20:52  |
StefanoSpataro
Messages: 2736
Registered: June 2005
Location: Torino
|
first-grade participant |
From: *10-79-r.retail.telecomitalia.it
|
|
Hi,
I have tried to apply the same change for the psi channel, with the following dec:
spataro@briareos:~/trunk/pandaroot/macro/run/tdrct/psi3770$ cat psi3770_fix.dec
noPhotos
#
Decay pbarpSystem
1.0 D+ D- VSS;
Enddecay
#
Decay D-
1.0 K+ pi- pi- PHSP;
Enddecay
#
Decay D+
1.0 K- pi+ pi+ PHSP;
Enddecay
#
End
The problem is that in this case pbarpSystem is not a vector, then I have the following error:
EvtGen:In readDecayFile, reading:psi3770_fix.dec
EvtGen:As requested, PHOTOS will be turned off.
EvtGen:VSS did not get the correct parent spin
pbarpSystem -> D+ D- (VSS):
EvtGen:Will terminate execution!
I am not sure on what this VSS model is doing, now the question if it we should put phase space as model, or set the initial spin pf pbarpSystem to 1 in the evt.pdl... but there is no reason that a pbar p collision would have only a spin 1!
I could put phase space, but before starting I would like to know what we should use exactly...
Ok, I will run with Phase Space to save some time, wating for some comment on this side.
[Updated on: Fri, 02 December 2011 21:11] Report message to a moderator |
|
|
|
|
|
|
|
|
|
GSI Forum
Search
Help
Members
Login
Home
