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The Quarks Inside Baryons. “3 quarks for Mr Mark” James Joyce - Finegan’s Wake. Quark properties. If protons and neutrons are made of quarks what properties must they have? They must conserve baryon number. They must conserve spin. They must conserve charge. Deep inelastic scattering.
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The Quarks Inside Baryons “3 quarks for Mr Mark” James Joyce - Finegan’s Wake
Quark properties • If protons and neutrons are made of quarks what properties must they have? • They must conserve baryon number. • They must conserve spin. • They must conserve charge.
Deep inelastic scattering • In search of the deep structure of the proton
Positively charged proton If an electron is fired at a proton at moderate speed, the electron behaves as expected. It has a negative charge and it is deviated from its path when it comes near the positive charge of the proton.
proton neutron u u d u d d
NEUTRON u d d ⅓+ ⅓+ ⅓ baryon no =1 ⅔+(-⅓)+(-⅓) charge =0
u u d ⅓+ ⅓+ ⅓ baryon no =1 ⅔+(⅔)+(-⅓) charge =1
particles uuu uud udd ddd
particles +2 3/2 3/2 +1 0 3/2 -1 3/2
HADRONS involved in strong interaction Baryons Mesons q q q
Mesons quark antiquark pairs
Strange Baryons • Live much longer than 10-23seconds • Generally around 10-10seconds Λ0Σ+ Σ-Σ0 Ξ0 Ξ-