The Constituent Quark Models. Outline. The Quark Model Original Quark Model Additions to the Original Quark Model Color Harmonic Potential Model Isgur-Karl Model M.I.T. Bag Model Assumptions Predictions. Constituent Quark Model (Non-relativistic).
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1964 The model was proposed independently by Gell-Mann and Zweig
Three fundamental building blocks 1960’s (p,n,l) Þ 1970’s (u,d,s)
mesons are bound states of a of quark and anti-quark:
Can make up "wave functions" by combining quarks:
baryons are bound state of 3 quarks:
proton = (uud), neutron = (udd), L= (uds)
anti-baryons are bound states of 3 anti-quarks:
The three parameters
ms,d , αs|ψ(0)|2, ω0
are obtained by fitting to
ms,d = 360MeV , ω0 =500MeV
(mu,d is not equal to ms).
(similar to electrodynamics of two slow moving fermions)
R - radius of the Bag
Nq = # of quarks inside the bag
B – bag constant that reflects the bag pressure
Fixing the only parameter of the model B, by fitting the mass of the nucleon to 938MeV we have first order predictions
αs – the strong coupling constant
Mq depends on the quantum no. of the coupled quarks
The masses of N, Δ, Ω, ω were used to fit the parameters.
Simple models can give us a very good picture!