What Are the Elementary Constituent s Of

8/14/2019 What Are the Elementary Constituent s Of

1/39


2/39

What arethe

Elementary

Constituents of Matter?

What are theforces that

control theirbehaviour at themost basic level?


3/39

History of Constituents of

Matter

AD


4/39


5/39

In Nuclear Reactions momentum and mass-energy is conserved for a closed system thetotal momentum and energy of the particles

present after the reaction is equal to the totalmomentum and energy of the particles before thereaction

In the case where an alpha particle is releasedfrom an unstable nucleus the momentum of thealpha particle and the new nucleus is the same as

the momentum of the original unstable nucleus


6/39

00011110 ++ epnLarge variations in the emission velocities of the particle seemed to indicate that both energy and

momentum were not conserved.This led to the proposal by Wolfgang Pauli of anotherparticle, the neutrino, being emitted in decay to carryaway the missing mass and momentum.

The neutrino (little neutral one) was discovered in 1956.

Wolfgang Pauli

__


7/39

00011110 ++ epn1.008665 u 1.007825 u 0.0005486 u

27

10660.1

1 u =1 J =

19106.1

__

kg

eV


8/39

0002914.0)0005486.0007825.1(008665.1

=

+=Mass difference

2710660.10002914.0 =

311083724.4 =

kg

kg

u


9/39

It has been found by experiment that the emitted beta particle

has less energy than 0.272 MeV

Neutrino accounts for the missing energy

2mcE=

2831 )100.3)(1083724.4( =

1410353516.4 =

271755

10602.1

10353516.4

19

14

=

=

J

J

eV

272.0= MeV


10/39


11/39

+

+


12/39

First artificial splitting ofnucleus

First transmutation using

artificially acceleratedparticles

First experimental verification

ofE= mc2

Irish Nobel Prize

E.T.S. Walton 1951

Cockroft and Walton

Ernest WaltonJohn Cockcroft


13/39


14/39

EnergyHeHeLiH 4242

73

11 +++

Proton + Lithium Two alpha particles + Energy

1 MeV 17.3 MeV

Experimental verification of

E

=mc2


15/39


16/39

Ancient Greeks:

Earth, Air, Fire,Water

By 1900, nearly 100

elements By 1936, back to three

particles: proton, neutron,

electron


17/39


18/39


19/39
http://particleadventure.org/frameless/chart_body.html


20/39


21/39

The Four Fundamental Forces


22/39


23/39


24/39

Particle

zoo

2c

Em =


25/39


26/39

mx 10101

mx15

101

mx 15107.0

mx 18107.0

Thomson (1897): Discovers electron


27/39

0001

6028

6027 ++ eNiCo

Q = -1e almost all trapped in atoms

Q= 0 all freely moving through universe

_


28/39


29/39


30/39

Just as the equation x2=4 can have twopossible solutions (x=2 OR x=-2), so

Dirac's equation could have two solutions,one for an electron with positive energy,and one for an electron with negativeenergy.

Dirac interpreted this to mean that forevery particle that exists there is acorresponding antiparticle, exactlymatching the particle but with opposite

charge. For the electron, for instance,there should be an "antielectron" calledthe positron identical in every way butwith a positive electric charge.


31/39

1928 Dirac predicted existence of antimatter

1932 antielectrons (positrons) found inconversion of energy into matter

1995 antihydrogen consisting of antiprotons andpositrons produced at CERN

++ ee

In principle an antiworld can be built fromantimatterProduced only in accelerators andin cosmic rays


32/39

+ + eerays


33/39

hfee 2++


34/39


35/39


36/39

James Joyce

Murray Gell-Mann
http://membres.lycos.fr/geryon/bio.htm


37/39


38/39

13

1

3

2

3

2+=++

03

1

3

1

3

2=+

3

2

+

3

1


39/39

http://lectureonline.cl.msu.edu/~mmp/applist/q/q.htm
http://lectureonline.cl.msu.edu/~mmp/applist/q/q.htmhttp://lectureonline.cl.msu.edu/~mmp/applist/q/q.htmhttp://lectureonline.cl.msu.edu/~mmp/applist/q/q.htm

Documents

What Are the Elementary Constituent s Of