Study of Basic Interactions (July Post, 2014)

 

In the study of the basic interactions which exist in nature, one of the most intriguing is the strong nuclear interaction. An important property of the strong interaction is that quarks and gluons are never seen in isolation, a phenomenon called "confinement". Such behavioural changes happen when the nuclear matter is heated to the extreme conditions. The "deconfined" quarks and gluons hence form a new state of nuclear matter, which has been called the Quark-Gluon Plasma (QGP). Just a few microseconds after the Big Bang, the universe is believed to have crossed the phase boundary, condensing from a QGP to a hadron gas as the temperature decreased. In the experimental front, producing the QGP in the laboratory and studying its properties is the main goal of experiments with heavy-ion collisions at high-energies. Among the probes of the QGP, the heavy quarks have generated interest due to their unique role in the diagnostics of the highly excited medium created in the relativistic heavy-ion collisions. Experimentally and theoretically, over the two decades, the properties of heavy quarkonium states (which are bound states of heavy quark-antiquark pairs, charmonium and bottomonium) in a hot and dense QCD medium have been extensively studied.

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