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I’ve never seen Santa Claus… I don’t believe in Santa Claus. I’ve never seen the Easter Bunny… I don’t believe in the Easter Bunny. Why????. I’ve never seen a quark But I believe in quarks. Don Lincoln The University of Michigan. Nucleon Constituents: The study of quarks, past and modern.
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I’ve never seen Santa Claus…I don’t believe in Santa Claus. I’ve never seen the Easter Bunny…I don’t believe in the Easter Bunny. Why???? I’ve never seen a quark But I believe in quarks. Don Lincoln The University of Michigan
Nucleon Constituents: The study of quarks, past and modern Don Lincoln The University of Michigan Or…... Yes Virginia, there are quarks…..
e’, k’ e, k ‘Simple’ electron-proton inelastic scattering ep e + stuff g, q }pn p { Uncomplicating the Complicated { { { { final state information strength + kinematics electron spin information proton initial state
e’, k’ e, k g, q }pn p { Complications Reduced Treat proton as composed of three non-interacting quarks, then let photon from electron knock one of them out of the proton.
Simplest electron-proton Scattering Before electron p e photon After e quark p debris q
Simplest electron-proton Scattering Before electron p e photon After e quark p debris q proton
Simplest electron-proton Scattering Before electron p e photon After e quark jet p debris proton q jet
Complicated electron-proton Scattering Before electron p e photon After e quark jet p debris proton q jet
Simplifying electron-proton Scattering Before electron p e photon After e quark jet p debris proton q jet cone
Lessons from Quark Scattering • The truth is hard. • Simplifying assumptions make the calculations easier. • Simplifying assumptions lie. • Choosing the right measurements makes the lies minor. • Many simple measurements have been made. Many complex measurements remain.