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Re: Problem with Xi(1820) in EvtGen [message #18622 is a reply to message #18621] Sun, 01 November 2015 17:03 Go to previous messageGo to previous message
Elisabetta Prencipe (2) is currently offline  Elisabetta Prencipe (2)
Messages: 214
Registered: February 2013
first-grade participant
 From: *hsi15.unitymediagroup.de
Hi Stefano,

Jenny and I have been thinking what would go wrong in that decay model. As apparently it looked everything correct, we have contacted the EvtGen developers. Effectively, it looks there is a bug in the model.
Briefly, the problem occur at the level of the class src/EvtGenBase/EvtMassAmp.cpp::amplitude().
A quick fix suggested by the authors is the following: to comment out


if ( _vb->L() != 0 ) {amp=0.;}

for the birth vertex factor (_vb) on line 78 in src/EvtGenBase/EvtMassAmp.cpp::amplitude() for the
case when the sum of the pole masses of the daughters is less than the parent pole mass.
Maybe Jenny can give a more detailed update during the next seevogh meeting. Now it looks working correctly.

cheers, Elisabetta

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