  Directed and elliptic flow measurements for charged pions and protons are
reported as a function of transverse momentum, rapidity, and centrality for 40
and 158A GeV Pb + Pb collisions as recorded by the NA49 detector. Both the
standard method of correlating particles with an event plane, and the cumulant
method of studying multiparticle correlations are used. In the standard method
the directed flow is corrected for conservation of momentum. In the cumulant
method elliptic flow is reconstructed from genuine 4, 6, and 8-particle
correlations, showing the first unequivocal evidence for collective motion in
A+A collisions at SPS energies.
