Title: History of Quantum Chromodynamics 
Speaker: Prof. Harald Fritzsch （LMU Physics Department） 
Moderator: Prof. Xing Zhizhong
Time: 15:00, Oct.17
Place: Room C305, IHEP Main Building 
Abstract: 
In 1971 Harald Fritzsch and Gell-Mann introduced the color quantum number of the quarks, which explained the bound state structure of the baryons and the decay rate of the neutral pion. One year later they discussed a gauge theory, based on the gauge group of the color transformations SU(3).This theory is similar to quantum electrodynamics, but the gauge bosons of QCD,the gluons, interact not only with the quarks, but also with themselves.This leads to the phenomenon of asymptotic freedom - the coupling constant decreases at high energies. This has been measured at SLAC, DESY, Fermilab and CERN. 
At very high energies there should exist a new state of matter, the quark-gluon-plasma, e.g. inside massive neutron stars or in nucleus collisions at high energy. Today the theory of quantum chromodynamics is considered to be the exact theory of the strong interactions and of the nuclear forces. 

About the speaker: 
After completing his education in Zwickau 1961, he became Soldier of the Nationale Volksarmee of the GDR. He studied Physics in Leipzig from 1963 to 1968. After fleeing to West Germany, he continued his studies in Munich where he finished his Ph.D. under the supervision of Heinrich Mitter.In 1970 Fritzsch visited the Aspen Center of Physics, where he met Murray Gell-Mann. They started a collaboration, first in Aspen, later at the California Institute of Technology. In 1971 they introduced the concept of the colour charge quantum number which allowed them in collaboration with William A. Bardeen to explain the decay rate of pions. In the fall of 1971 Fritzsch and Gell-Mann moved to Geneva in Switzerland, where they worked together at CERN. They proposed a gauge theory for the strong interaction,which now is called Quantumchromodynamics. In September 1972 they moved back to Caltech. In 1975 Fritzsch published a paper together with Peter Minkowski in which they proposed the symmetry group SO(10) as the symmetry of the grand unified theory which has become a standard theory.In 1976 Fritzsch moved to CERN. After working for one year at the University of Wuppertal and the University of Bern, Fritzsch became professor at the Ludwig Maximilian University of Munich in 1980.Fritzsch worked also on "composite models" of leptons and quarks, mass matrices of quarks and leptons, weak decays of heavy quarks, cosmology and the fundamental constants of physics. He retired in 2008.