However, a naive mixture of electroweak theory and the quark model led to calculations about known decay modes that contradicted observation: in particular, it predicted Z boson-mediated "flavor-changing" decays of a strange quark into a down quark, which were not observed. A 1970 idea of Sheldon Glashow, John Iliopoulos, and Luciano Maiani, known as the GIM mechanism, showed that the flavor-changing decays would be strongly suppressed if there were a fourth quark, "charm", that paired with the strange quark. This work led, by the summer of 1974, to theoretical predictions of what a charm + anticharm meson would be like. These predictions were ignored. The work of Richter and Ting was done for other reasons, mostly to explore new energy regimes. In the Brookhaven group, Glenn Everhart, Terry Rhoades, Min Chen, and Ulrich Becker were the first to discern a peak at 3.1 GeV in plots of production rates. This was the first recognition of the "J". Hadronic decay modes of are strongly suppressed because of the OZI Rule. This effect strongly increases the lifetime of the particle and thereby gives it its very narrow decay width of just . Because of this strong suppression, electromagnetic decays begin to compete with hadronic decays. This is why the has a significant branching fraction to leptons. The primary decay modes are: In a hot QCD medium, when the temperature is raised well beyond the Hagedorn temperature, the and its excitations are expected to melt. This is one of the predicted signals of the formation of the quark–gluon plasma. Heavy-ion experiments at CERN's Super Proton Synchrotron and at BNL's Relativistic Heavy Ion Collider have studied this phenomenon without a conclusive outcome as of 2009. This is due to the requirement that the disappearance of mesons is evaluated with respect to the baseline provided by the total production of all charm quark-containing subatomic particles, and because it is widely expected that some are produced and/or destroyed at time of QGP hadronization. Thus, there is uncertainty in the prevailing conditions at the initial collisions. In fact, instead of suppression, enhanced production of is expected in heavy ion experiments at LHC where the quark-combinant production mechanism should be dominant given the large abundance of charm quarks in the QGP. Aside of , charmed B mesons (), offer a signature that indicates that quarks move freely and bind at-will when combining to form hadrons.