Studies of QCD matter from E178 and E451 at NAL to CMS

at LHC

Wit Busza

MIT

In the early 70’s we were interested in the question “what is the nature of the matter that exists in the short interval between the initial collision of two high energy protons and the production of the asymptotic state of the outgoing hadrons?”. 40 years later we still do not have a clear answer to this question. Our focus has shifted to a seemingly more difficult question “what is the nature of the matter produced shortly after the collision of two ultra relativistic nuclei?”. With the advent of the RHC and LHC heavy ion colliders a new field, full of exciting and unexpected results, has emerged. I will briefly review, from a personal perspective, the evolution of this physics and discuss what we have learnt to date about the “condensed matter of QCD”.