| 1 | /*
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| 2 | * ---- Delphes ----
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| 3 | * A Fast Simulator for general purpose LHC detector
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| 4 | * S. Ovyn ~~~~ severine.ovyn@uclouvain.be
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| 5 | *
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| 6 | * Center for Particle Physics and Phenomenology (CP3)
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| 7 | * Universite Catholique de Louvain (UCL)
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| 8 | * Louvain-la-Neuve, Belgium
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| 9 | * */
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| 10 |
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| 11 | #include "interface/BFieldProp.h"
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| 12 | #include "TRandom.h"
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| 13 |
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| 14 | #include <iostream>
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| 15 | #include <sstream>
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| 16 | #include <fstream>
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| 17 | #include <iomanip>
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| 18 |
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| 19 | #include<cmath>
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| 20 |
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| 21 |
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| 22 | using namespace std;
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| 23 |
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| 24 |
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| 25 | //------------------------------------------------------------------------------
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| 26 |
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| 27 | TrackPropagation::TrackPropagation() {
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| 28 |
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| 29 | MAXITERATION = 10000;
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| 30 | MINSEGLENGTH = 70;
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| 31 |
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| 32 | }
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| 33 |
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| 34 | void TrackPropagation::Propagation(const TRootGenParticle *Part,TLorentzVector &genMomentum)
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| 35 | {
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| 36 |
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| 37 | double q = Charge(Part->PID);
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| 38 | if(q==0)return;
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| 39 |
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| 40 | float Xvertex1 = Part->X;
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| 41 | float Yvertex1 = Part->Y;
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| 42 | float Zvertex1 = Part->Z;
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| 43 |
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| 44 | //out of trackibg coverage?
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| 45 | if(sqrt(Xvertex1*Xvertex1+Yvertex1*Yvertex1) > TRACK_radius){return;}
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| 46 | if(fabs(Zvertex1) > TRACK_length){return;}
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| 47 |
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| 48 | float Px = Part->Px;
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| 49 | float Py = Part->Py;
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| 50 | float Pz = Part->Pz;
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| 51 |
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| 52 | double px = Px / 0.003;
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| 53 | double py = Py / 0.003;
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| 54 | double pz = Pz / 0.003;
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| 55 | double pt = sqrt(px*px+py*py);
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| 56 | double p = sqrt(px*px+py*py+pz*pz);
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| 57 |
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| 58 | if(q!=0){
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| 59 | double M = Part->M;
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| 60 | double vx = px/M;
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| 61 | double vy = py/M;
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| 62 | double vz = pz/M;
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| 63 |
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| 64 | double Bx = TRACK_bfield_x;
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| 65 | double By = TRACK_bfield_y;
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| 66 | double Bz = TRACK_bfield_z;
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| 67 |
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| 68 | double ax = (q/M)*(Bz*vy - By*vz);
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| 69 | double ay = (q/M)*(Bx*vz - Bz*vx);
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| 70 | double az = (q/M)*(By*vx - Bx*vy);
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| 71 | double dt = 1/p;
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| 72 | if(pt<266 && vz < 0.0012) dt = fabs(0.001/vz);
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| 73 |
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| 74 | double xold=Xvertex1; double x=xold;
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| 75 | double yold=Yvertex1; double y=yold;
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| 76 | double zold=Zvertex1; double z=zold;
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| 77 |
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| 78 | double VTold = sqrt(vx*vx+vy*vy);
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| 79 |
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| 80 | int k = 0;
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| 81 |
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| 82 | while(k < MAXITERATION){
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| 83 | k++;
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| 84 |
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| 85 | vx += ax*dt;
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| 86 | vy += ay*dt;
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| 87 | vz += az*dt;
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| 88 |
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| 89 | double VTratio = VTold/sqrt(vx*vx+vy*vy);
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| 90 | vx *= VTratio;
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| 91 | vy *= VTratio;
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| 92 |
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| 93 | ax = (q/M)*(Bz*vy - By*vz);
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| 94 | ay = (q/M)*(Bx*vz - Bz*vx);
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| 95 | az = (q/M)*(By*vx - Bx*vy);
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| 96 |
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| 97 | x += vx*dt;
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| 98 | y += vy*dt;
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| 99 | z += vz*dt;
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| 100 |
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| 101 | if( (x*x+y*y) > TRACK_radius*TRACK_radius ){ x /= (x*x+y*y)/(TRACK_radius*TRACK_radius); y /= (x*x+y*y)/(TRACK_radius*TRACK_radius); break;}
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| 102 | if( fabs(z)>TRACK_length)break;
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| 103 |
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| 104 | xold = x;
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| 105 | yold = y;
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| 106 | zold = z;
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| 107 | }
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| 108 |
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| 109 | if(x!=0 && y!=0 && z!=0)
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| 110 | {
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| 111 | double eta;
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| 112 | float Theta = atan2(sqrt(x*x+y*y),z);
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| 113 | eta = -log(tan(Theta/2));
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| 114 | double phi = atan2(y,x);
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| 115 | genMomentum.SetPtEtaPhiE(Part->PT,eta,phi,Part->E);
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| 116 | }
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| 117 | }
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| 118 | }
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