Generalized hydrodynamical models

The assumptions on the initial state in the Landau hydrodynamical model are difficult to accommodate inside the present ideas on the dynamics in hadron-hadron collisions, in particular in connection with the leading particle properties. The model is generalized to permit an interpretation in terms of the notions employed in the valence-quark-gluon models of the van Hove-Pokorski type. The main assumption is that the valence quarks in general will pass by each other leaving the (neutral) remainder of the hadronic matter in a state described by a simple wave mode of an ideal relativistic gas. In such a state there is a precise coupling between the internal state (described by temperature) and the state of motion of the fluid elements. In particular, some parts of the hadronic matter are at rest at high temperature, while other parts are 'carried away' by the valence quarks with a temperature decreasing with increasing velocity. It is assumed that some parts of this hadronic matter which are left in a state with rapidity less than a constant y0 develop into the final state principles populating the centre of phasespace. In this case there is a one-to-one correspondence between the initial state of the hadronic matter and the asymptotic energy and multiplicity distributions of the secondaries in the centre of phase space. Formulas permitting a determination of this initial state from experimental results are derived and some simple examples analyzed. (Auth.)