The must fundamental constituents of matter

Physics 100

Chapt 26

Anaximenes

Anaximenes ~600BC

All types of matter areformed from different combinations of:

•Earth•Air•Fire•Water

Closer to home

Earth

Wind

Fire

Water

Elements

Anaximenes idea

• Good point: Economical– All of matter reduced to 4 easy-to-remember

components

• Bad point: Wrong– Alchemists (including Isaac Newton) tried for

centuries to changing one chemical element into another with no success

Enter Mendeleev

All matter is comprised of different combinations of(now 92) different chemical elements

Good point Correct; successfully predicted the existence of

Scandium, Gallium & Germanium

Bad point Uneconomical; 92 basic constituens

Rutherford

All elements are constructedfrom 3 basic particles:

•electrons

•neutrons•protons

Feel the strong force

& are heavy hadrons

Doesn’t feel the strong

force & is light lepton

The “elementary particles” circa 1935

Category particle symbol charge mc2 strong electric weak

Leptons electron e- -1 0.511 MeV

no yes yes

neutrino 0 ~0 no no yes

Hadrons proton p +1 938.3MeV

yes yes yes

neutron n 0 939.6MeV

yes yes yes

Light photon 0 0 no yes no

Economy is restored

Forces felt

These “good” times

didn’t last long

Paul Adrien Maurice Dirac

1902 - 1984

Combined relativity

&QuantumMechanics

p = mV

xpx = mVx

E = 1/2 mv2

py = mVy

y

Pre relativity

px can be + or -

E is always +

p = mV

xpx = mVx

E = mc22 2( )

E = mc2±

py = mVy

y

px can be + or -

E also can be + or -

Post relativity:

QM waves: =h/p f=E/h

Pre relativity:

p = m0 v (v =p/m0)

E =1/2 m0v2 =p2/2m0

= h/p can be + or f=p2/2m0h always +

QM waves: =h/p f=E/h

after relativity:

p = m0 v (v =p/m0)

E2 = (mc2 )2 E= ± mc2

= h/p can be + or

f= can be + or mc2

h

Negative wavelength : wave in backward direction.

Negative frequency : wave backward in time????

What does it mean to move backwards in time?

backward time motion

t

B

when viewed forward in time:

L R

: C

: P

When antimatter comes in contact

with matter,

what happens?

- +- +- +

Anti-hydrogen

p

+

Anti-hydrogen atoms are made routinely at the CERN laboratory in Switzerland.

It is found to have the same size and allowed energy levels as ordinary hydrogen

Anti-Carbon

+

+

++

+

+

•antielectrons

•antineutrons•antiprotons

Although it would be impossibly difficult to make anti-atoms more complex than anti-hydrogen, it is in principle possible

CP Violation:

Asymmetry matteranti-

matter

Big Bang

matter-antimattersymmetric

all matterno

antimatter

Our research

Where did all theanti-people go???

Include anti-particles in our list

Category particle symbol charge mc2 symbol charge

Leptons electron e- -1 0.511 MeV

positron e+ +1

neutrino 0 ~0 anti-neutrino

0

Hadrons proton p +1 938.3MeV

anti-proton

p -1

neutron n 0 939.6MeV

anti-neutron

n 0

Light photon 0 0 photon 0

anti-particleparticle

Quantum Electro-Dynamics (QED)

Combined Relativity, Quantum Mechanics and Photons into one single theory

Richard Feynman Julian SchwingerShinichiro Tomonaga

QED explains action-at-a-distance

QED is a fabulously accurate theory

QEDtheory

measure

Strength of electrons magnetic field:

Ideas of QEDstrong nuclear force

Hideki Yukawa

Short range (10-15m) of the strong nuclear force:predicts existence of a “” particle Mc2 140 MeV

1935

Look for in cosmic rays

“Spark chamber” tracks

+ and – particle discovered in cosmic rays

m+c2 = m-c2 = 106 MeV

Near expectations

for Yukawa’s

Experiments show that the + & - do not feel the Strong Nuclear Force and,

therefore, cannot be Yukawa’s

the + & - are additional leptons(i.e. like the e+ & e- but with larger mass)

Yukawa’sfinally discovered in 1947

In fact there are 3 of them:

+ M+c2 = 139.6 MeV

0 M0c2 = 135.0 MeV

- M-c2 = 139.6 MeV

Anti-particles

Photographicemulsion

“Atom smashers”

Inside the accelerator tunnel

e+e- collider

Belle Detector

Electronic detectors

Fermilab (near Chicago)

2 km

detector

Inside a Fermilab Tunnel

Biggest of all is in Europe

~5 miles

Detectors

Neutrino interacts in a Bubble Chamber

Leptons (circa 2005)anti-particleparticle

name symbol charge mc2 name symbol charge

electron e -1 0.511 MeV

positron e +1

electron neutrino

e 0 ~0 anti-elec neutrino

e 0

muon +1 105.7MeV

anti-muon

+1

muon- neutrino

0 ~0 anti-mu neutrino

0

tau -1 1876 MeV

anti-

tau +1

tau- neutrino

0 ~0 anti-tau neutrino

0

1950’s & 1960’s, Many other particles are discovered

p-

M=1116MeV

K0 “meson”

K0 -

M=498 MeV

Two classes of hadrons

Baryons (p, n, , …..)

ultimate decay products include a proton

Mesons (, K, …)

ultimate decay products e’s, ’s & ’s

Both baryons & mesons feel the Strong Nuclear Force

Lots of baryons have been discovered

& even more mesons

The elementary particle chart revisited

Economy is lost!!

6 leptons: e e; ;

(+ 6 anti-leptons)

Category particle symbol

Leptons electron e-

neutrino Hadrons proton p

neutron n

1935 NOW

hundreds of hadrons + anti-hadrons

Elementary Particle Zoo

Lepton House

Electrons,

Muons,Taus,

& lots of neutrinos

Hadron Savannah

100’s of Baryons,

Latest new Mesons

+anti particles galore

& lots of photons

Special today:

live pions being exhanged

proton

neutron