Diagram of High Energy Nuclear Collisions

Many new particles, mostly hadrons, are produced in high energy collisions between atomic nuclei. The most popular models describing the hadron production process are based on the creation, evolution and decay of resonances, strings or quark-gluon plasma. The validity of these models is under vivid discussion, and it seems that a common framework for this discussion is missing. Here we introduce the diagram of high energy nuclear collisions, where domains of the dominance of different hadron-production processes in the space of laboratory-controlled parameters, the collision energy and nuclear-mass number of colliding nuclei, are indicated. We argue, the recent experimental results locate boundaries between the domains, allowing for the first time to sketch an example diagram. Finally, we discuss the immediate implications for experimental measurements and model development following the sketch.