8/14/2019 What Are the Elementary Constituent s Of
1/39
8/14/2019 What Are the Elementary Constituent s Of
2/39
What arethe
Elementary
Constituents of Matter?
What are theforces that
control theirbehaviour at themost basic level?
8/14/2019 What Are the Elementary Constituent s Of
3/39
History of Constituents of
Matter
AD
8/14/2019 What Are the Elementary Constituent s Of
4/39
8/14/2019 What Are the Elementary Constituent s Of
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
8/14/2019 What Are the Elementary Constituent s Of
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
__
8/14/2019 What Are the Elementary Constituent s Of
7/39
00011110 ++ epn1.008665 u 1.007825 u 0.0005486 u
27
10660.1
1 u =1 J =
19106.1
__
kg
eV
8/14/2019 What Are the Elementary Constituent s Of
8/39
0002914.0)0005486.0007825.1(008665.1
=
+=Mass difference
2710660.10002914.0 =
311083724.4 =
kg
kg
u
8/14/2019 What Are the Elementary Constituent s Of
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
8/14/2019 What Are the Elementary Constituent s Of
10/39
8/14/2019 What Are the Elementary Constituent s Of
11/39
+
+
8/14/2019 What Are the Elementary Constituent s Of
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
8/14/2019 What Are the Elementary Constituent s Of
13/39
8/14/2019 What Are the Elementary Constituent s Of
14/39
EnergyHeHeLiH 4242
73
11 +++
Proton + Lithium Two alpha particles + Energy
1 MeV 17.3 MeV
Experimental verification of
E
=mc2
8/14/2019 What Are the Elementary Constituent s Of
15/39
8/14/2019 What Are the Elementary Constituent s Of
16/39
Ancient Greeks:
Earth, Air, Fire,Water
By 1900, nearly 100
elements By 1936, back to three
particles: proton, neutron,
electron
8/14/2019 What Are the Elementary Constituent s Of
17/39
8/14/2019 What Are the Elementary Constituent s Of
18/39
8/14/2019 What Are the Elementary Constituent s Of
19/39
http://particleadventure.org/frameless/chart_body.html8/14/2019 What Are the Elementary Constituent s Of
20/39
8/14/2019 What Are the Elementary Constituent s Of
21/39
The Four Fundamental Forces
8/14/2019 What Are the Elementary Constituent s Of
22/39
8/14/2019 What Are the Elementary Constituent s Of
23/39
8/14/2019 What Are the Elementary Constituent s Of
24/39
Particle
zoo
2c
Em =
8/14/2019 What Are the Elementary Constituent s Of
25/39
8/14/2019 What Are the Elementary Constituent s Of
26/39
mx 10101
mx15
101
mx 15107.0
mx 18107.0
Thomson (1897): Discovers electron
8/14/2019 What Are the Elementary Constituent s Of
27/39
0001
6028
6027 ++ eNiCo
Q = -1e almost all trapped in atoms
Q= 0 all freely moving through universe
_
8/14/2019 What Are the Elementary Constituent s Of
28/39
8/14/2019 What Are the Elementary Constituent s Of
29/39
8/14/2019 What Are the Elementary Constituent s Of
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.
8/14/2019 What Are the Elementary Constituent s Of
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
8/14/2019 What Are the Elementary Constituent s Of
32/39
+ + eerays
8/14/2019 What Are the Elementary Constituent s Of
33/39
hfee 2++
8/14/2019 What Are the Elementary Constituent s Of
34/39
8/14/2019 What Are the Elementary Constituent s Of
35/39
8/14/2019 What Are the Elementary Constituent s Of
36/39
James Joyce
Murray Gell-Mann
http://membres.lycos.fr/geryon/bio.htm8/14/2019 What Are the Elementary Constituent s Of
37/39
8/14/2019 What Are the Elementary Constituent s Of
38/39
13
1
3
2
3
2+=++
03
1
3
1
3
2=+
3
2
+
3
1
8/14/2019 What Are the Elementary Constituent s Of
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