Problem 496

Summary:	pi- production spectrum from proton (10GeV/c) interaction does not fit the experimental data
Product:	Geant4	Reporter:	tumakov
Component:	processes/hadronic	Assignee:	Hans-Peter.Wellisch
Status:	RESOLVED FIXED
Severity:	normal
Priority:	P2
Version:	5.0
Hardware:	Other
OS:	Linux
URL:	http://meco.ps.uci.edu/~tumakov/geant4_probems.html

Description tumakov 2003-05-29 13:58:20 CEST

pi-  production spectrum from proton (10GeV/c) interaction does not fit the
experimental data:
 Simulated pi- spectra in different Geant4 hadron codes (MARS,QGSC,PRECO) have
peaks in forward and backward directions and almost zero production into
intermediate angles. Hadron code from DMX example gives a little bit more pions
into 0<theta<180deg region but insufficient with acomparison to experimental
spectrum.
  FLUKA from GEant3 simulation gives correct pion spectrum
(with probably factor 2 lower multiplicity which is minor problem).
It will be good to implement similar code in Geant4.

pi- spectrum parametrization is available in C++ code, if it is possible some
how use it in proton beam simulation with tracing of proton secondary
interactions, it will be usefull too...

The shape of experimental spectrum, simulated spectra from all available codes,
and C++ parametrization of pi- spectrum you can find on my web page:
http://meco.ps.uci.edu/~tumakov/geant4_probems.html

	Regards, Vladimir Tumakov

Comment 1 Hans-Peter.Wellisch 2003-06-26 02:32:59 CEST

Hi Vladimir,

  thank you for the information. I'll try and come with a physics list to give
you a better description.

Many greetings,

Hans-Peter.

Comment 2 Hans-Peter.Wellisch 2003-07-31 08:20:59 CEST

Hi,

  I have looked into this now rather deeply, and find that there is no current
physics list for your case. Still we likely can do better than what you found
with geant3. The best I can offer currently is our quark gluon string model
implementation. To get it, you can pick the QGSP physics list for WWW.

You then will have to edit one of the builders from the Packaging package:
HadronPhysicsQGSP.cc

Please replace
  thePro.RegisterMe(&theQGSPPro);
  thePro.RegisterMe(&theLEPPro);
  theLEPPro.SetMaxEnergy(25*GeV);
with
  thePro.RegisterMe(&theQGSPPro);
  theQGSPPro.SetMinEnergy(5*GeV);
  thePro.RegisterMe(&theLEPPro);
  theLEPPro.SetMaxEnergy(5.1*GeV);

I have put a few plots into
/afs/cern.ch/user/h/hpw/public/ForTumakov
reproducing some of the distributions you show.
They seem reasonable, or at least better than your
geant3 plots.

Many greetings,

Hans-Peter.