void TwoBodyDecay(Particle &parent, Particle &daughter1, Particle &daughter2, double thetad, double phid){
double mom = TriangleFunc(parent.m, daughter1.m, daughter2.m);
daughter1.ThreeMomentum(mom*sin(thetad)*cos(phid),mom*sin(thetad)*sin(phid),mom*cos(thetad));
daughter2.ThreeMomentum(-mom*sin(thetad)*cos(phid),-mom*sin(thetad)*sin(phid),-mom*cos(thetad));
daughter1.Lorentz(parent);
daughter2.Lorentz(parent);
Link_Particles(parent,daughter1);
Link_Particles(parent,daughter2);
}
//isotropic decay for parent -> daughter1 + daughter2
void TwoBodyDecay(Particle &parent, Particle &daughter1, Particle &daughter2){
double thetad = acos(Random::Flat(-1,1));
double phid = Random::Flat(0,1)*2*pi;
double mom = TriangleFunc(parent.m, daughter1.m, daughter2.m);
daughter1.ThreeMomentum(mom*sin(thetad)*cos(phid),mom*sin(thetad)*sin(phid),mom*cos(thetad));
daughter2.ThreeMomentum(-mom*sin(thetad)*cos(phid),-mom*sin(thetad)*sin(phid),-mom*cos(thetad));
daughter1.Lorentz(parent);
daughter2.Lorentz(parent);
Link_Particles(parent,daughter1);
Link_Particles(parent,daughter2);
}
// cascade decay for parent -> mediator + X, mediator > daughter1 + daughter 2
//This assumes no meaningful propagation before the decay occurs
void DecayDM(Particle &daughter1, Particle &daughter2, Particle &mediator, Particle &parent){
double pmx, pmy, pmz, Em, pm;
double ym, zm, thetam, phim;
double pdx, pdy, pdz, Ed, pd;
double yd, zd, thetad, phid;
double lam;
//double polarX1, polarX2;
//Particle darkphoton(MV);
ym = Random::Flat(0,1);
zm = Random::Flat(0,1);
thetam = acos(-1+2*ym);
phim = 2.0*pi*zm;
double Md, Mm, Mp;
Md = daughter1.m;
Mm = mediator.m;
Mp = parent.m;
lam = lambda(1,Mm*Mm/Mp/Mp,0);
Em = Mp/2.0*(1.0+Mm*Mm/Mp/Mp);
pm = Mp/2.0*sqrt(lam);
pmx = pm*sin(thetam)*cos(phim);
pmy = pm*sin(thetam)*sin(phim);
pmz = pm*cos(thetam);
mediator.FourMomentum(pmx,pmy,pmz,Em);
// boost darkphoton to lab frame
mediator.Lorentz(parent);
// generate dark matter momentum in dark photon rest frame
yd = Random::Flat(0,1);
zd = Random::Flat(0,1);
thetad = acos(-1+2*yd);
phid = 2.0*pi*zd;
lam = lambda(1,Md*Md/Mm/Mm,Md*Md/Mm/Mm);
Ed = Mm/2.0;
pd = Mm/2.0*sqrt(lam);
pdx = pd*sin(thetad)*cos(phid);
pdy = pd*sin(thetad)*sin(phid);
pdz = pd*cos(thetad);
daughter1.FourMomentum(pdx,pdy,pdz,Ed);
daughter2.FourMomentum(-pdx,-pdy,-pdz,Ed);
// boost dark matter particles to lab frame
daughter1.Lorentz(mediator);
daughter2.Lorentz(mediator);
//cout << parent.name << " " << parent.end_coords[0] << " " << parent.end_coords[1] << " " << parent.end_coords[2] << endl;
Link_Particles(parent,mediator);
Link_Particles_Immediate(mediator,daughter1);
Link_Particles_Immediate(mediator,daughter2);
//cout << daughter1.name << " " << daughter1.end_coords[0] << " " << daughter1.end_coords[1] << " " << daughter1.end_coords[2] << endl;
//cout << daughter2.name << " " << daughter2.end_coords[0] << " " << daughter2.end_coords[1] << " " << daughter2.end_coords[2] << endl;
}
/*I should check that this is handled properly. Not quite sure that it is, though
it probably won't change very much if the angle is handled differently.
*/
void DecayDM_Off_Shell(Particle &daughter1, Particle &daughter2, Particle &mediator, Particle &parent, double theta){
TwoBodyDecay(mediator, daughter1, daughter2, theta);
mediator.ThreeMomentum(0,0,TriangleFunc(parent.m,mediator.m,0));
daughter1.Lorentz(mediator);
daughter2.Lorentz(mediator);
double mtheta=acos(Random::Flat(-1,1));
double mphi = Random::Flat(0,1)*2*pi;
mediator.Rotate_z(mtheta);
mediator.Rotate_y(mphi);
daughter1.Rotate_z(mtheta);
daughter1.Rotate_y(mphi);
daughter2.Rotate_z(mtheta);
daughter2.Rotate_y(mphi);
mediator.Lorentz(parent);
daughter1.Lorentz(parent);
daughter2.Lorentz(parent);
Link_Particles(parent,mediator);
Link_Particles_Immediate(mediator,daughter1);
Link_Particles_Immediate(mediator,daughter2);
}
// two body decay of parent -> daughter + X (e.g. Pi0 -> gamma + V)
// output momentum of daughter particle in the lab frame
void DecayDP(Particle &daughter, Particle &parent){
double pdx, pdy, pdz, Ed, pd;
double thetad, phid;
double lam;
thetad = acos(-1+2*Random::Flat(0,1));
phid = Random::Flat(0,2.0*pi*Random::Flat(0,1));
double Md, Mp;
Md = daughter.m;
Mp = parent.m;
lam = lambda(1,Md*Md/Mp/Mp,0);
Ed = Mp/2.0*(1.0+Md*Md/Mp/Mp);
pd = Mp/2.0*sqrt(lam);
pdx = pd*sin(thetad)*cos(phid);
pdy = pd*sin(thetad)*sin(phid);
pdz = pd*cos(thetad);
daughter.FourMomentum(pdx,pdy,pdz,Ed);
// boost darkphoton to lab frame
daughter.Lorentz(parent);
Link_Particles(parent,daughter);
}
