Soft QCD path to the mass hierarchy
  The study of the quantization of the QCD string with the helix structure is put into the context of a decades-long discussion opposing the probabilistic and the deterministic interpretations of the quantum theory. The recent evolution of the string fragmentation model (to a large extent driven and confirmed by the empirical evidence), towards the deterministic point of view is recounted: the notion of causality not only paves a way to the study of mass spectrum, it also resolves a long-standing ambiguity about the nature of the so-called Bose-Einstein correlations. Two directions for the further development of the model are outlined: 1/ the elimination of soft collinear divergencies, 2/ the relation between the topological properties of the QCD string and the emergence of new particle types (quantum numbers). 
Sarka Todorova-Nova
hep-ph