Nick van Eijndhoven wrote: > > Dear friends, > Note that for the pseudo-rapidity (eta) one can write > > eta=-log(tan(theta/2.)) > > where theta is the angle (in rad) w.r.t. the beam direction. > > This makes things a lot easier. > Realize however, that by introducing a GetPseudoRapidity() > memberfunction one imposes the user to define the z-axis > as the beam direction. This may sometimes give limitations. > I would say it's better to provide 3-vector components > and let the user determine the pseudorap. him/her self. no problem, you can write: TVector3 beamdirection; TVector3 v; ... Double_t eta = -log(tan(v.Angle(beamdirection)/2.)); Peter
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