message: Avoid usage of acos in calculation of Armenteros variables
diff: @@ -710,12 +710,15 @@ void AliESDv0KineCuts::Armenteros(AliESDv0* const v0, Float_t val[2]) const
  TVector3 vecP(mp[0],mp[1],mp[2]);
  TVector3 vecM(mm[0],mm[1],mm[2]);
  - Double_t thetaP = acos((vecP * vecM)/(vecP.Mag() * vecM.Mag()));
  - Double_t thetaN = acos((vecN * vecM)/(vecN.Mag() * vecM.Mag()));
  -
  - Double_t alfa = ((vecP.Mag())*cos(thetaP)-(vecN.Mag())*cos(thetaN))/
  - ((vecP.Mag())*cos(thetaP)+(vecN.Mag())*cos(thetaN)) ;
  - Double_t qt = vecP.Mag()*sin(thetaP);
  + Double_t costhetaP = (vecP * vecM)/(vecP.Mag() * vecM.Mag());
  + Double_t costhetaN = (vecN * vecM)/(vecN.Mag() * vecM.Mag());
  + Double_t sin2thetaP = 1 - costhetaP*costhetaP;
  + Double_t sinthetaP = 0;
  + if(sin2thetaP>0) sinthetaP=TMath::Sqrt(sin2thetaP);
  +
  + Double_t alfa = ((vecP.Mag())*costhetaP-(vecN.Mag())*costhetaN)/
  + ((vecP.Mag())*costhetaP+(vecN.Mag())*costhetaN) ;
  + Double_t qt = vecP.Mag()*sinthetaP;
  val[0] = alfa;
  val[1] = qt;
  