147 lines
3.4 KiB
C++
147 lines
3.4 KiB
C++
#ifndef decay_h
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#define decay_h
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#include "TVector3.h"
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#include "../Cleopatra/ClassIsotope.h"
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//=======================================================
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//#######################################################
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// Class for Particle Decay
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// B --> d + D
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// input : TLorentzVector, emitting particle
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// output : scattered TLorentzVector
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//=======================================================
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class Decay{
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public:
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Decay();
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~Decay();
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double GetQValue() { return Q;}
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double GetAngleChange(){
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TVector3 vD = PD.Vect();
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TVector3 vB = PB.Vect();
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vD.SetMag(1);
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vB.SetMag(1);
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double dot = vD.Dot(vB);
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return TMath::ACos(dot)*TMath::RadToDeg() ;
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}
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double GetThetaCM() { return theta * TMath::RadToDeg();}
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double GetCMMomentum(){ return k;}
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TLorentzVector GetDaugther_d() {return Pd;}
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TLorentzVector GetDaugther_D() {return PD;}
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void SetMotherDaugther(int AB, int zB, int AD, int zD){
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Isotope Mother(AB, zB);
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Isotope Daugther_D(AD, zD);
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Isotope Daugther_d(AB-AD, zB-zD);
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mB = Mother.Mass;
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mD = Daugther_D.Mass;
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md = Daugther_d.Mass;
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double Q = mB - mD - md;
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printf("====== decay mode : %s --> %s + %s, Q = %.3f MeV \n", Mother.Name.c_str(), Daugther_d.Name.c_str(), Daugther_D.Name.c_str(), Q);
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isMotherSet = true;
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}
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int CalDecay(TLorentzVector P_mother, double ExB, double ExD, double normOfReactionPlane = 0){
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if( !isMotherSet ) {
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return -1;
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}
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this->PB = P_mother;
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double MB = mB + ExB; ///mother
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double MD = mD + ExD; ///Big_Daugther
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Q = MB - MD - md;
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if( Q < 0 ) {
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this->PD = this->PB;
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dTheta = TMath::QuietNaN();
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k = TMath::QuietNaN();
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return -2;
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}
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//clear
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TLorentzVector temp(0,0,0,0);
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PD = temp;
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Pd = temp;
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k = TMath::Sqrt((MB+MD+md)*(MB+MD-md)*(MB-MD+md)*(MB-MD-md))/2./MB;
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//in mother's frame, assume isotropic decay
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theta = TMath::ACos(2 * gRandom->Rndm() - 1) ;
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//for non isotropic decay, edit f1.
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//theta = TMath::ACos(f1->GetRandom());
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double phi = TMath::TwoPi() * gRandom->Rndm();
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PD.SetE(TMath::Sqrt(mD * mD + k * k ));
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PD.SetPz(k);
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PD.SetTheta(theta);
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PD.SetPhi(phi);
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Pd.SetE(TMath::Sqrt(md * md + k * k ));
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Pd.SetPz(k);
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Pd.SetTheta(theta + TMath::Pi());
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Pd.SetPhi(phi + TMath::Pi());
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PD.RotateY(TMath::Pi()/2.);
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PD.RotateZ(normOfReactionPlane);
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Pd.RotateY(TMath::Pi()/2.);
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Pd.RotateZ(normOfReactionPlane);
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//Transform to Lab frame;
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TVector3 boost = PB.BoostVector();
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PD.Boost(boost);
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Pd.Boost(boost);
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return 1;
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}
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private:
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TLorentzVector PB, Pd, PD;
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double mB, mD, md;
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double theta;
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TF1 * f1;
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bool isMotherSet;
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double Q;
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double k; // momentum in B-frame
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double dTheta; // change of angle
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};
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Decay::Decay(){
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TLorentzVector temp(0,0,0,0);
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PB = temp;
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Pd = temp;
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PD = temp;
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mB = TMath::QuietNaN();
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mD = TMath::QuietNaN();
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md = TMath::QuietNaN();
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theta = TMath::QuietNaN();
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k = TMath::QuietNaN();
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Q = TMath::QuietNaN();
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dTheta = TMath::QuietNaN();
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isMotherSet = false;
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f1 = new TF1("f1", "(1+ROOT::Math::legendre(2,x))/2.", -1, 1);
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}
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Decay::~Decay(){
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delete f1;
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}
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#endif |