//-------------------------------------------------------------------------
#include "AliVParticle.h"
+#include "TMath.h"
ClassImp(AliVParticle)
return *this;
}
+
+Bool_t AliVParticle::Local2GlobalMomentum(Double_t p[3], Double_t alpha) const {
+ //----------------------------------------------------------------
+ // This function performs local->global transformation of the
+ // track momentum.
+ // When called, the arguments are:
+ // p[0] = 1/pt * charge of the track;
+ // p[1] = sine of local azim. angle of the track momentum;
+ // p[2] = tangent of the track momentum dip angle;
+ // alpha - rotation angle.
+ // The result is returned as:
+ // p[0] = px
+ // p[1] = py
+ // p[2] = pz
+ // Results for (nearly) straight tracks are meaningless !
+ //----------------------------------------------------------------
+ if (TMath::Abs(p[0])<=kAlmost0) return kFALSE;
+ if (TMath::Abs(p[1])> kAlmost1) return kFALSE;
+
+ Double_t pt=1./TMath::Abs(p[0]);
+ Double_t cs=TMath::Cos(alpha), sn=TMath::Sin(alpha);
+ Double_t r=TMath::Sqrt(1 - p[1]*p[1]);
+ p[0]=pt*(r*cs - p[1]*sn); p[1]=pt*(p[1]*cs + r*sn); p[2]=pt*p[2];
+
+ return kTRUE;
+}
+
+Bool_t AliVParticle::Local2GlobalPosition(Double_t r[3], Double_t alpha) const {
+ //----------------------------------------------------------------
+ // This function performs local->global transformation of the
+ // track position.
+ // When called, the arguments are:
+ // r[0] = local x
+ // r[1] = local y
+ // r[2] = local z
+ // alpha - rotation angle.
+ // The result is returned as:
+ // r[0] = global x
+ // r[1] = global y
+ // r[2] = global z
+ //----------------------------------------------------------------
+ Double_t cs=TMath::Cos(alpha), sn=TMath::Sin(alpha), x=r[0];
+ r[0]=x*cs - r[1]*sn; r[1]=x*sn + r[1]*cs;
+
+ return kTRUE;
+}
+
+Bool_t AliVParticle::Global2LocalMomentum(Double_t p[3], Short_t charge, Double_t &alpha) const {
+ //----------------------------------------------------------------
+ // This function performs global->local transformation of the
+ // track momentum.
+ // When called, the arguments are:
+ // p[0] = px
+ // p[1] = py
+ // p[2] = pz
+ // charge - of the track
+ // alpha - rotation angle.
+ // The result is returned as:
+ // p[0] = 1/pt * charge of the track;
+ // p[1] = sine of local azim. angle of the track momentum;
+ // p[2] = tangent of the track momentum dip angle;
+ // Results for (nearly) straight tracks are meaningless !
+ //----------------------------------------------------------------
+ double pt = TMath::Sqrt(p[0]*p[0]+p[1]*p[1]);
+ if (pt == 0.) return kFALSE;
+ alpha = TMath::Pi() + TMath::ATan2(-p[1], -p[0]);
+
+ p[0] = 1./pt * (float)charge;
+ p[1] = 0.;
+ p[2] = p[2]/pt;
+
+ return kTRUE;
+}
+
+Bool_t AliVParticle::Global2LocalPosition(Double_t r[3], Double_t alpha) const {
+ return Local2GlobalPosition(r, -alpha);
+}
+