The research interests of Professor John Harris are focused on understanding the behavior of nuclear, hadronic and partonic matter at high energy densities. Quantum Chromodynamics calculations on a lattice predict that a transition from normal nuclear or hadronic matter to a deconfined phase of matter consisting of freely interacting quarks and gluons, known as the quark-gluon plasma (QGP), will occur at extremely high energy densities above approximately 2 GeV/fm[superscript 3]. This corresponds to a temperature of 2 x 10 [superscript 12] Kelvin. Such energy densities are predicted to have existed a few microseconds after the Big Bang and are expected in collisions of heavy nuclei at ultrarelativistic energies. Formation and discovery of the QGP is the primary purpose of ultrarelativistic nucleus-nucleus experiments at the new Relativistic Heavy Ion Collider (RHIC) at Brookhaven Laboratory on Long Island in New York and at the future Large Hadron Collider at CERN in Geneva, Switzerland.

John Harris was involved in the original proposal to initiate a nucleus-nucleus experimental program at CERN to search for a possible QGP phase transition, and has been an active member in the planning, conceptual design, construction, data aquisition and physics of ultrarelativistic nucleus-nucleus experiments NA35 and NA49 at CERN, and the STAR (Solenoidal Tracker at RHIC) experiment at Brookhaven. He was the founding spokesperson for STAR from 1991 until 2002. Present research activities focus on identifying the QGP and determining its properties. This currently involves experimental investigation using STAR at RHIC on Long Island (NY), design of a comprehensive new experiment for a higher luminosity RHIC to understand quantitatively properties of the QGP, and possibly utilizing ultrarelativistic collisions of heavy nuclei at the LHC at CERN.