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Re: DPM theta cut off [message #13905 is a reply to message #13904] Wed, 29 August 2012 11:28 Go to previous messageGo to previous message
Simone Bianco is currently offline  Simone Bianco
Messages: 29
Registered: January 2009
continuous participant
From: *
Dear Donghee,

the work of Thomas and the results of some discussions of one year ago about the theta_min parameter were included in the PndDpmDirect class.
Johan introduced the parametrization of theta_min in the implementation of the ctor PndDpmDirect::PndDpmDirect(Double_t Mom, Int_t Mode, Long_t Seed):

PndDpmDirect::PndDpmDirect(Double_t Mom, Int_t Mode, Long_t Seed) {
// Calculate ThtMin first. For this we make a cut-off on the value of -t of 1e-2 GeV^2 (~100 MeV/c momentum)
// This estimated from a parametrization found in thesis of Thomas Wuerschig (figure 6.4, page 121): 
// Roughly: 0.4 deg at 15 GeV/c and 4 deg at 1.5 GeV/c, lineair interpolation in double log-scale.
Double_t logangle = TMath::Log(0.4)+(TMath::Log(15.)-TMath::Log(Mom))*(TMath::Log(4)-TMath::Log(0.4))/(TMath::Log(15)-TMath::Log(1.5));
Double_t ThtMin = TMath::Exp(logangle);

 PndDpmDirect(Mom, Mode, Seed, ThtMin) ;

so if you use this ctor you don't need to calculate by hands a value for theta_min, since this is automatically obtained as a function of the beam momentum.

I hope this helps.


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