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Quarkonia

Quarkonia. [Secs 16.6, 16.7 Dunlap]. The Discovery of Charm - 1974. Burton Richter (1931) Samuel Ting (1936).

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Quarkonia

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  1. Quarkonia [Secs 16.6, 16.7 Dunlap]

  2. The Discovery of Charm - 1974 Burton Richter (1931) Samuel Ting (1936) Richter and Ting shared the 1976 Nobel Prize for discovering the charmed particle, except it was not really the charmed particle – but a charmed – anticharmed meson - CHARMONIUM

  3. c c The discovery of Charmonium Charmonium is the bound state of a charm and anticharm quark – bound together with gluons. Charmonium was discovered in two laboratories independently and at the same time. Richter and workers at SLAC discovered it in collisions. Richter called it the “ Ψ particle” Ting and workers at BNL (Brookhaven Nat. Lab) discovered it in proton collisions on Beryllium. Ting called it the “J particle” IT BECAME KNOWN AS THE J/Ψ

  4. The e+ e- discovery of Charmonium When the center of mass energy was tuned to exactly 3.097GeV amazing things started happening. The production of hadrons went up went crazy Note the logarithmic scale The production of muons also went crazy.

  5. Charmonium is a long-lived state? Well it does live a long time - we know it because the line width of its production is so small ~ 0.068 MeV. [This is why they missed it at CERN!] Its lifetime from Heisenberg’s uncertainty principle is: This is about 10,000 times slower than a normal strong interaction decaying particle which at this energy would be ~ 10-24s

  6. Why is Charmonium so long lived? Physicist Zweig worked it out – it is now called “Zweig’s rule” If a J/Ψ decays into 3xπ or 2xK it can do so strongly – BUT the mediating boson must be colorless (color charge cannot be exposed!). This required at least 3 gluons – as shown. The chances of having a 3 gluon exchange is very low. But why don’t we see a normal strong decay like. The answer - there is simply not enough energy.

  7. Broad states appear above 3.7GeV The R- value shows the amount of hadronic jets produced at each energy. We see another sharp production at 3686MeV. This is as a result of an excited state in charmonium. The broad excited states at higher energies result from 2D decay.

  8. c c The 4 quarkonia b u s b u s Updownium The Pion Strangeonium Charmonium Bottomium

  9. The decay of Strangeonium On phase space grounds this decay should be fast But this decay is much much faster – Why?

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