NA61/SHINE: Hadron Production In p+p/A And A+A Interactions At The Cern SPS

The physics motivations, status and plans of NA61/SHINE experiment are presented. Also the first, preliminary results on $π^−$ production, from the pilot run in 2007, are shown. These data are needed by the T2K experiment for precise neutrino beam simulation. It is explained why the precise hadron production measurements are crucial for various fields of physics. Moreover, it is argued that the 2D scan in system size and collision energy is essential for the study of the onset of deconfinement and search for the critical point of strongly interacting matter.