If I remember well, a good class TLorentzVector was previously in ROOT. Using it one could easily do boosts to some other frames like:
TLorentzVector v; v.Boost(bx, by, bz);
Now instead of this user-friendly class the Reference Guide suggest to use two independent classes ROOT::Math::PxPyPzEVector and ROOT::Math::Boost with zero information on how to use them together. Moreover, the ROOT::Math::Boost class seems to be broken.
ROOT::Math::Boost b(bx, by, bz); $ undefined reference to `ROOT::Math::Boost::SetComponents(double, double, double)'
So, what is now the procedure of boosts to another frame? If there is a working method or it’s better to still use the old TLorentzVector class?