Mark-J was one of the experiments involved in the discovery of the gluon in 1979. Data taking at PETRA, the at that time highest energy e⁺e^– collider in the world at DESY, Hamburg (Germany) started in December '78 and within a year the existence of the intermediary of the strong interaction, the source of fire in sun and stars, was established. The first statistically relevant sample of 3-jet events due to hard gluon radiation were shown by Mark-J [1] in August at the Lepton-Photon Conference held at Fermilab, Chicago, followed by presentations of the other PETRA groups Tasso, Pluto and Jade. The rate and shape of the 3-jet events were in agreement with the predictions of the theory of interacting quarks and gluons, Quantum Chromo-Dynamics [2,3].

This website is organised around several pages. How the Dutch involment in the experiment came about is told in the introduction. The formation of the collaboration in the early years before the start of PETRA can also be found there. Information on the various publications, the Dutch theses and my seminars before and after the discovery of the three jet events complete this part of the website. The main part of the site is formed by the collection of photographs of PETRA and the installation of the experiment with all its people. The still controversial issue of the discovery of the gluon and how to answer the question; "Who really was first and deserves the ultimate credit?", is still not settled. My opinion on this matter can be found in the publication In Search of Gluons.

References

1. Mark-J Collaboration, D.P.Barber et al.;Discovery of Three-Jet Events and a Test of Quantum Chromodynamics at PETRA;Phys.Rev.Lett. 43(1979) 830.
2. H.Fritsch,M.Gell-Mann,H.Leutwyler; Advantages of the Color Octet Gluon Picture; Phys.Lett. 47B(1973) 365 and references therein.
3. J.Ellis,M.K.Gaillard,G.G.Ross; Search for Gluons in e⁺e^- Annihilation; Nucl.Phys. B111(1976) 253.