38 lines
1.9 KiB
C++
38 lines
1.9 KiB
C++
inline std::tuple<TVector3,TVector3,double> find_PC_PathLength(const TVector3& x1, const TVector3& x2) {
|
|
/*
|
|
Function that finds the path length between anode and cathode surfaces, both one-sheet hyperboloids of form (x*x+y*y)/(a*a) - (z*z)/(c*c) = 1
|
|
* path length found for a given particle moving along a certain direction from x1 to x2
|
|
* Typical arguments here will be x1=r_rhoMin, x2=qqqevent.pos or sx3event.pos
|
|
*/
|
|
TVector3 dx = x2-x1;// direction vector
|
|
double t2 = 1.0; //The value of 't' at the destination point, by definition: t=(z(t)-z0)/dz
|
|
auto onesheet_hyperboloid_intersect = [&](double a, double c) {
|
|
auto A = pow(dx.Perp(),2)/(a*a) - pow(dx.Z(),2)/(c*c);
|
|
auto B = 2*(dx.X()*x1.X()+dx.Y()*x1.Y())/(a*a) - 2*(dx.Z()*x1.Z())/(c*c);
|
|
auto C = pow(x1.Perp(),2)/(a*a) - pow(x1.Z(),2)/(c*c) - 1.0;
|
|
double disc = B*B - 4*A*C;
|
|
if(disc<0)
|
|
return TVector3(0,0,54321);
|
|
else {
|
|
double tsol1 = (-B + TMath::Sqrt(disc))/(2*A);
|
|
double tsol2 = (-B - TMath::Sqrt(disc))/(2*A);
|
|
if(tsol1 >= 0 && tsol1 <= t2)
|
|
return x1+tsol1*dx;
|
|
else if(tsol2>=0 && tsol2 <= t2)
|
|
return x1+tsol2*dx;
|
|
else
|
|
return TVector3(0,0,54321);
|
|
}
|
|
};
|
|
|
|
//TODO: Magic numbers here describing waist 'a', and flare 'c' will need better treatment.
|
|
//Currently, these are derived by fitting the crossover points to R^2/a^2 - z^2/c^2 = 1 for anodes
|
|
// Cathode a, c values are found by scaling up the anode waist by 43/37, the ratio of the outermost radii
|
|
TVector3 anode_intersect = onesheet_hyperboloid_intersect(32.0429,301.895);
|
|
TVector3 cathode_intersect = onesheet_hyperboloid_intersect(37.239045,301.895);
|
|
if(anode_intersect.Z()!=54321 && cathode_intersect.Z()!=54321)
|
|
return std::tuple(cathode_intersect,anode_intersect,(cathode_intersect-anode_intersect).Mag()*0.1);
|
|
else
|
|
return std::tuple(TVector3(0,0,0), TVector3(0,0,0), 54321);
|
|
}
|