// Consider two normal vectors, i.e. along the x and y axes in the local coordinate system
    TVector3 normVec(cos(euler_phi), sin(euler_phi), 0);
    TVector3 normVecPerp(cos(euler_phi + M_PI_2), sin(euler_phi + M_PI_2), 0);

It is not important bur more simple
// Consider two normal vectors, i.e. along the x and y axes in the local coordinate system
    TVector3 normVec       ( cos(euler_phi), sin(euler_phi), 0);
    TVector3 normVecPerp(- sin(euler_phi), cos(euler_phi), 0);
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