The idea that hadrons might be combinations of simpler more fundamental particles occurred to a number of physicists.In 1964 Gell-Mann and Zweig suggested that the meson nonet and baryon octet and decuplet could all be derived by combining three distinct spin – 1/2 particles, and their associated antiparticles. These new fundamental particles were called quarks. In 1967 Feynman suggested an intuitive model of what hapens when protons conteining quarks collide with other particles. He was able to derive certain characteristics of scattering that could be related back to the quark/parton model. In 1968 Freidman, Kendall and Taylor directed high-energy electrons at protons at SLAC(Stanford Linear Accelerator Center).One thing stood out, the pattern of scattering was the same at all collision energies. They discovered that they could account for the scattering by identifying the partons with quarks and introducing some additional particles moving between the quarks.1
Deep inelastic scattering – when high-energy electron beams were fired at fixed targets some of electrons suffered large angle scatterings rather like those of the alfa particles in original Rutherford scattering experiment.
The electrons must be interacting with highly concentrated charged particles inside the protons.The scattering takes place via the exchange ofhigh-energy photon.3
The 1990 Nobel Prize for Physics was shared by Friedman, kenall and Taylor for their pioneering investigations concerning deep inelastic scattering of electrons on protons and bound neutrons, which have been of essential importance for the development of quark model in particle physics….
Quark is hypothetical particle that carries a fractional charge. There are four different kinds of quarks, each having antiparticle called Antiquark. These quarks are called:
The Up Quark (u)
The Down Quark (d)
The Strange Quark (s)
The Charm Quark (c)
The charges on the four quarks u, d, s, c are +2/3, -1/3, -1/3, +2/3 that of the electron charge. Antiquarks have opposite charges. All quarks and antiquarks have equal spins which is ½. These quarks combine to form different elementary particles. For example: Protonsare composed of three quarks (uud) and neutrons (udd). Each meson can be conceived as the union of a quark and an antiquark.



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