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Evidence for Quarks Quark Composition of Hadrons

Evidence for Quarks Quark Composition of Hadrons. [Secs 15.1 - 15.4 Dunlap]. By 1964 Particle classification became:. LEPTONS (E-W). HADRONS (S+E-W). Leptons. Baryons. FERMION. Mesons. BOSON. Gauge Bosons. g i. Not substantiated until 70s and 80s. Young man, if I could

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Evidence for Quarks Quark Composition of Hadrons

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  1. Evidence for Quarks Quark Composition of Hadrons [Secs 15.1 - 15.4 Dunlap]

  2. By 1964 Particle classification became: LEPTONS (E-W) HADRONS (S+E-W) Leptons Baryons FERMION Mesons BOSON Gauge Bosons gi Not substantiated until 70s and 80s

  3. Young man, if I could remember the names of all these particles, I would have been a botanist The 1950s particle Explosion Enrico Fermi In th 1950s the race was on to build larger and larger accelerators. Many physicists such as Fermi were alarmed to say the least. By the end of the 50s we had the: Then in 1964 the cascades were discovered The situation was getting out of hand – some solution had to be found

  4. The quark or “straton” model or hadrons Three Quarks for Muster Mark! James Joyce Finnegans Wake 1964. Murray Gell-Mann and George Zweig tentatively put forth the idea of quarks. They suggested that mesons and baryons are composites of three quarks or antiquarks, called up, down, or strange (u, d, s) with spin 1/2 and fractional electric charge. u d s charges 2/3, -1/3, -1/3 Since the charges had never been observed, the introduction of quarks was treated more as a mathematical explanation. Later theoretical and experimental developments allow us to now regard the quarks as real physical objects, even though they cannot be isolated.

  5. Evidence for quark structure [1] Neutral pi meson production: Such reactions are difficult to explain if it is assumed that the proton is like the electron a fundamental structureless particle. [2] Neutron and proton magnetic moments are not = the nuclear magneton as predicted by the Dirac equation for point fermions.

  6. Other evidences for quark structure Deep Inelastic Scattering of electrons The proton has excited states

  7. Particle classification with 3 quarks LEPTONS (E-W) HADRONS (S+E-W) Quarks Leptons Baryons FERMION Mesons BOSON Gauge Bosons gi Not substantiated until 70s and 80s

  8. Mathematics – SU(2) symmetryspecial unitary group Singlet Triplet Di-Nucleon Deuteron Bound

  9. mathematics – SU(3) symmetry plet singlet octet octet Decuplet The strange quark is seen as being the identical particle to the up and down quark – just in a different quantum state. Rotations in quark space do not change the strong interaction

  10. SU3 found in experiment PROTON FAMILY = OCTET Jπ= 1/2+ HEAVY PROTON FAMILY = dicuplet Jπ=3/2+

  11. In reality the strange quark “s” has a heavier intrinsic mass PROTON OCTET FAMILY HEAVY PROTON – DECUPLET FAMILY

  12. Discovery of the Omega Minus The bubble chamber photograph shown was taken in 1964 – It shows the production of the first observed Omega Minus

  13. A look quick look at all the quarks c t u Q=+2/3 Q= -1/3 d s b 1st Gen 2nd Gen 3rd Gen

  14. SU3 symmetry for q-q system

  15. The Pi- Meson Family (of nine)

  16. The energies of the Pi-meson family The higher mass of the K- mesons and Eta meson results from the larger mass of the strange quark

  17. MESONS

  18. BARYONS

  19. Adding the charmed quark

  20. Particle classification became LEPTONS (E-W) HADRONS (S+E-W) Quarks Leptons Baryons FERMION Mesons BOSON Gauge Bosons gi Not substantiated until 70s and 80s

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