基本粒子

基本粒子基本粒子

2

The Periodic Table

Mendeleev (1869) introduced the periodic table

Discovery of Electron• J.J. Thomson found that Cathode rays are electrons

A陽極

O陰極

O’狹縫

CC’平行面板

B

E

C

C’

圖一Pluecher (Germany) found cathode rays in 18581870s Crookes (British) studied this extensively

·all metals ·-charge turn in magnetic field Like X-rays (Hertz, etc.)

·unaffected by e-field · can penetrate Al foil

3

4

The Structure of AtomsRutherford (1912)showed that atomscontain a centralnucleus

Electrons orbit nucleuswith well-definedenergy and ill-definedpositions10

-10 m

5

The Structure of Nuclei

Nucleus containsprotons with charge+e and unchargedneutrons

10-15

m

J. Chadwick (1932)discovered neutron 2α

4 + 4Be9 6 C12 + 0n

1

6

10-15

m

The Structure of NucleonsNeutrons and protons contain quarks

“Seen” in the deep inelatsticep scattering at SLAC (1967)

7

The Constituents of Matter

Protons contain uud - charge = +eNeutrons contain udd - charge = 0

quarks electron

23

e+

13

e- -e

charge

u

d e

8

Proton Decay?

50000 tons pure water•τp>1035 years (Experiment)

•τp~1036 years (GUT theory)

Super- Kamiokande experiment is 1,000 m underground in Mozumi Mine

11000 photomultiplier tubes

Cherenkov radiatio

n

9

Prediction of Antimatter

Paul Dirac predicted existence of the positron in 1928

Dirac’s equation implies:

positron mass = electron mass

positron charge = +e

10

Discovery of Antimatter

Anderson (1932) discovered the positronpredicted by Dirac

11

Production of e+e- Pairs

High energy -ray becomes an electron-positron pair

e+e-

E = mc2

12

Antimatter Disappears in a Matter Dominant

World

e+ e-

Inverse process also occurs, electrons and positrons annihilate to produce photons (energy)

E = mc2

13

The Fundamental Particles

u

d

tc

s b

six quarks

1947

1976 1995

1978

e

e

six leptons

1956

1895

1963

1936 1973

Along with their anti-particle partners

Spin ½ fermions

14

Basic Interactions

15

A Colorless World

Quarks

Leptons

u c t

d s b

Charge=+2/3

Charge=-1/3

πMeson

Λ Baryon

Mesons: π,ρ,Φ,k,B…

Baryons: p,n,Λ,Σ,Δ…

e μ τ

νμ νe ντ

NeutrinosCharge=0

Charge=-1Mediator

γ G Z0 W ±

?graviton ?graviton

2005/12/9 物理光耀世界 (Ⅱ)- 紀念 1905 物理奇蹟年的一百週年 16

Evolution of the Universe

The Universe began with a “Big Bang” about 15 billion years ago

-270o

?

heavy elements formed in stars

stars and galaxies exist, atoms form

neutrons

quark "soup"

15 billion years

1 million years

1 second

10-10

1015deg 1010deg109deg

6000o

-255o

3 minuteshelium nuclei formed

microwave background radiation fills universe

300,000 years

4000o

life on earth, molecules form

dominates matter

and protons formed

1 billion years

s

Big Bang

Big Bang

17

Discovery of Parity Violation

C.S. WU

Co60

B field

e-

e

Madame Wu measured the asymmetry in the beta decay rate of Co60

and found parity was maximally violated

In 1957