The elliptic flow for Lambda hyperons was measured by the NA49 experiment in semicentral (σ / σ tot <23.5%) Pb+Pb collisions at 158 A GeV. The standard method of correlating particles with an event plane has been used. Measurements of v2 near mid-rapidity are reported as a function of rapidity, centrality and transverse momentum and compared with CERES results. Studies of the elliptic flow of
K0S mesons are also in progress.
Elliptic flow of Lambda particles increases both with the impact parameter and with the transverse momentum but exhibits no significant dependence on rapidity around mid-rapidity. It is compared with v2 for pions and protons as well as with hydrodynamic and Blast Wave model predictions. Elliptic flow of Lambda hyperons rises linearly with transverse momentum and is smaller than v2 for pions and protons. Both these features are well reproduced by the Blast Wave parametrization and the hydrodynamic model. The increase of v2 with pt is weaker at SPS than at RHIC energy and is significantly overpredicted by hydrodynamical calculations.