Quarks, the dreams that stuff is made of Micro-world Macro-world Lect 19

Hadron “zoo” ~1963 mesons baryons

The elementary particle chart revisited Economy is lost!! 4 leptons: e e ;   (+ 4 anti-leptons) Categoryparticlesymbol Leptons electron e-e- neutrino Hadrons proton p neutron n hundreds of hadrons + anti-hadrons

1963: All hadrons known at that time are composites of 3 types of “quarks” and “anti-quarks” (their antiparticles) (& 3 antiquarks) u -2/3 d +1/3 s +1/3 u +2/3 d -1/3 s -1/3 Marray Gell-Mann 3 quarks George Zweig “up” “down” “strange”

Simple Rules: Mesons: qq n: u +2/3 +:+: d -1/3 u -2/3 d +1//3 u +2/3 -:-: d -1/3 Baryons: qqq s 1/3 K0:K0: d -1/3 p: u +2/3 d -1/3 u +2/3 :: d -1/3 s -1/3

Simple Rules (cont’d): p: u -2/3 d +1/3 u -2/3 anti-baryons: qqq n: u -2/3 d +1/3 d 1/3 :: u -2/3 d +1/3 s 1/3

Prediction s -1/3 In the Baryon Tables at that time there was no entry that matched the s -1/3 s -1/3 s -1/3 combination Gell-Mann called the s -1/3 s -1/3 s -1/3 combination the   and predicted its Mass & other properties 1965: the   awas discovered at the Brookhaven Lab in NY. It’s mass & other properties agreed with predictions

Hadron “zoo” ~1965 mesons baryons !!!

Looking for sub-structure in 1905 Scattering of a few  -particles at wide angles was evidence for the atomic nucleus It was necessary that the a-particles had a deBroglie wave-length  size of nucleus = h/p large p The Rutherford experiment

Looking for substructure in 1970 = h/p Need larger p

Stanford 2-mile-long accelerator = m World’s most powerful micrcope ~3km

Scatter electrons from protons q q q Occasionally an electron scatters at a very large angle, Verifying expectations for quarks

1970 version of Rutherford’s expt

Quark theory: pros & cons Pros –Explains zoo of hadrons economically –Verified by high energy electron scattering experiments Cons –Isolated quarks have never been seen –No explanation for qqq=baryon & qq = meson rule –Problems with Pauli exclusion principle

 s -1/3 three s-quarks in the same quantum state This violates my exclusion principle Wolfgang Pauli

The strong interaction “charge” of each quark comes in 3 different varieties Y. Nambu M.-Y. Han s -1/3 the 3 s -1/3 quarks in the  - have different strong charges & evade Pauli -

“color” charges Important: The quarks do not really have different visual colors. It is convenient to name the different types of quark charges after colors because of similarities in the rules for combining them

Attractive configurations 3 primary colors color + complement same as the rules for combining colors to get white antiquarks:  anticolor charges Hence theory’s name = Quantum Chromodynamics quarks: qqq  color charges qqq explains the qqq=baryon & qq = meson rules

In QCD: force between quarks due to exchange of “gluons”

Why are isolated quarks never seen? Pulling quarks apart is like trying to separate the 2 ends of a rubber band. 2 new mesons!!!

“snapping” between quarks and hadrons D+D+ D-D-

1974: “charmed quark” discovered Annihilation of 2 billion eV e - & 2 billion eV e + e  e +  D + D  or D 0 D 0 Particles containing a +2/3 “charmed” quark c +2/3

Charmed quark is +2/3rds partner of the strange quark (& 4 antiquarks) u -2/3 d +1/3 s +1/3 u +2/3 d -1/3 s -1/3 4 quarks “up” “down” “charmed” “strange” c +2/3 c -2/3 1975

Hadron “zoo” ~1975 mesons baryons charmed baryons charmed mesons

Add bottom (1978) and top (1995) This little bump was 1 st evidence for the existence of charge -1/3 rd “bottom” quark The “top” quark) (charge = +2/3 rds ) was produced in very high energy proton- antiproton collisions.

UH & the top quark

Total = six quarks (& 6 antiquarks) u -2/3 d +1/3 s +1/3 u +2/3 d -1/3 s -1/3 6 quarks “up” “down” “charmed” “strange” c +2/3 c -2/3 Today b -1/3 “top” “bottom” t +2/3 b +1/3 t -2/3

Six quarks more graphically

Hadron “zoo” 2005 mesons baryons bottom baryons bottom mesons

The elementary particle chart revisited Categoryparticlesymbol Leptons electron e-e- neutrino Hadrons proton p neutron n Economy is recovered 1935 NOW Leptons quarks (more-or-less)

Four basic forces Name Propagat’d by Strong gluons Electro- magnetic photons Weak W  & Z 0 Gravity gravitons Strongest Weakest

Elementary Particles 2005 Gravity Graviton Mass=0

Is that all there is? Sun planet v F = G MsMpr2MsMpr2 F = M p a = M p v2rv2r G MsMpr2MsMpr2 = M p v2rv2r G MsrMsr v 2 = V =  GM s r

Solar system rotation curve V =  GM s r

Milky Way Galaxy Flat!!

Galaxies must be surrounded by a huge amount of unseen “dark matter” What we see What we don’t see

What is “dark matter” No one knows –It’s not neutrinos or unseen stars or planets –Maybe some as-yet undiscovered particle What we do know is that there is lots of it –Much more than ordinary matter Big mystery for physicists & astronomers –Problem for the 21 st century’s Einstein –Jaekeum Lee (our TA) is looking for it