  In proton-proton collisions at LHC energies, Z and low mass Higgs bosons
would be produced with high and predominantly longitudinal boost with respect
to the beam axis. This note describes a new analysis tool devised to handle
this situation in cases when such bosons decay to a pair of tau-leptons. The
tool reconstructs the rest frame of the tau+tau- pair by finding the boost that
minimises the acollinearity between the visible tau decay products. In most
cases this gives a reasonable approximation to the rest frame of the decaying
boson. It is shown how the reconstructed rest frame allows for a new method of
mass estimation. Also a considerable gain in sensitivity to helicity
correlations is obtained by analysing the tau-jets in the reconstructed frame
instead of using the laboratory momenta and energies, particularly when both
tau-leptons decay hadronically.
