The Story of Quarksthe first two, then three…eventually 6…quarks or partons

all hadrons made up of quarks to “explain” their quantum numbers

…partons to describe their scattering behavior

bubble chamber recordings

all “strange” particlesmade in association

with each other

…they come in pairs

invent a new “charge,”

strange charge

that is conserved

…see how the Λ got its name

Fig 46-11a, p.1528

Discovery of the Omega-

the octets of the Eightfold Way…

spin = ½ = ↑↑↓ spin = 0 = ↑↓

B=1 baryons, “nucleon-like” B=0, mesons, “generalized pions”

bary = heavy, > 1 GeV meso = medium weight, 0.1 -0.5 GeV

Q = charge, S = strangeness

really nonets and decuplets

the excited nucleon, the Δ++ resonance…width lifetime

the hunt for the omega minus…spin = 3/2 = ↑↑↑ B=1 …the decuplet

family of 4 excited → nucleons

doubly charged ↓

Ω-

some examples:

all conceivable combinations of quark & antiquark found…and nothing else

all conceivable combinations of 3 quark found…and nothing extra

in the end, 6 quarks discovered…the t (top) only a few years ago

we study the point-like electron with point-like neutrinos

W+

-1/3

+2/3

probing the quarks with point-like neutrino

…behave identically as electrons

individual current quarks inside composite particle scatter

remaining mystery…the problem of mass:

if you scatter quarks with electrons or neutrinos, you get mu ~ 5 MeV, md ~ 7 MeV, …the vast majority of the momentum is carried by gluons!

naively dividing the rest mass of the composite particles among quark constituents, you get much different rest energies: