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[codex] Fix Guan cosmic muon normalization #151

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Merged
lobis merged 1 commit into from
May 18, 2026
Merged

[codex] Fix Guan cosmic muon normalization #151

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5 changes: 3 additions & 2 deletions src/TRestGeant4PrimaryGeneratorInfo.cxx
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Original file line number Diff line number Diff line change
Expand Up @@ -460,11 +460,12 @@ TF2 TRestGeant4PrimaryGeneratorTypes::EnergyAndAngularDistributionFormulasToRoot
// Guan formula from https://arxiv.org/pdf/1509.06176.pdf
// muon rest mass is 105.7 MeV
// energy in keV
// already integrated in phi (*2pi): formula returns (counts/cm2/s)/keV/rad(theta)
// Original Guan formula is differential in solid angle. The final factor integrates over
// azimuth and converts dOmega to 2*pi*sin(theta)*dtheta, so do not add another 2*pi here.
const char* title = "Cosmic Muons Energy and Angular";
auto f =
TF2(title,
"2*TMath::Pi()*1E-6*0.14*TMath::Power(x*1E-6*(1.+3.64/"
"1E-6*0.14*TMath::Power(x*1E-6*(1.+3.64/"
"(x*1E-6*TMath::Power(TMath::Power((TMath::Power(TMath::Cos(y),2)+0.0105212-0.068287*"
"TMath::Power(TMath::Cos(y),0.958633)+0.0407253*TMath::Power(TMath::Cos(y),0.817285)"
")/(0.982960),0.5),1.29))),-2.7)*(1./"
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