The Forces of Nature

1
The Forces of Nature
Professor Peter Kalmus Queen Mary University of
London
2
Gravity
Inverse square law

• Force
• Always attractive
• Infinite in range
• Dominant for large objects

distance
3
Gravitational constant G
G ? 6.67 x 10-11 N m2 kg-2
Cavendish 1798 Torsion balance
Top view
quartz torsion fibre
Side view
4
This is classical (Newtonian) gravity
General relativity ? curvature of
space-time Quantum gravity ? no decent theory
yet
outside the scope of this talk
5
Inverse square law
Sun
v
Mo
a
Kepler, Newton T2 4 p2 a3 /G Mo v2 G Mo/a
(circular orbit)
6
The Earth is pulling us strongly towards its
centre
Why are we not there ?
?
What force is stopping us?
?
Electromagnetism
(together with the laws of quantum physics)
7
Electromagnetism
Inverse square law
8
Size of Atoms
Electrostatics need supply energy to pull
apart, i.e. to increase size of atom
However Uncertainty Principle
If try to squash atom ? r is reduced ? (D r) is
reduced ?(D p) is increased ? p is increased ?
need more energy
position momentum
Size of atoms is determined by Electromagnetism
and Quantum Physics
9
Chemistry
Electron clouds
far apart
Concentration of negative charge attracts nuclei
and binds molecule

• Residual effects
• chemical bonds
• molecules
• self-replication

10
Structures Planets and Mountains
Balance between gravity electromag
Minimum radius of spherical Planets (made of
rock)
Gravitat. force at root (weight) can break
melts directionality of bonds between
atoms
11
Forces of Nature
carrier Boson
12
Forces by exchange
Analogy only Useful mental picture ?
13
Attraction
14
Todays building blocks
proton u u d 2/3 2/3 -1/3 1 neutron u d
d 2/3 -1/3 -1/3 0
15
Todays building blocks
proton u u d 2/3 2/3 -1/3 1 neutron u d
d 2/3 -1/3 -1/3 0
4 particles very simple multiply by 3
(generations) multiply by 2 (antiparticles)
First generation
16
Also antileptons antiquarks
6 leptons 6 antileptons
6 quarks 6 antiquarks
muon m- -1 m-neutrino nm 0
charm c 2/3 strange s -1/3
tau t- -1 t-neutrino nt
0
top t 2/3 bottom b -1/3
17
Unification
of the fundamental forces of nature
Faraday, Maxwell
Newton
Electricity
Magnetism
Apples
Planets
Electro- magnetic
Gravity
18
Unification
of the fundamental forces of nature
Do the W and Z particles really exist ?
19
Solar fusion
H ? He
proton ? neutron positron neutrino u u d
u d d u ? d
p p ? d e n ( x 2 ) d p
? 3He g ( x 2 ) 3He 3He ? 4He p p
4p ? 4He 2e 2 n
20
Solar Fusion
Feynman diagram
The process q ? W q does not conserve
energy
W could exist for short time, hence travel
limited distance. The heavier the W, the shorter
the distance, hence short range of weak force.
21
To create a real W
Change outgoing quark into incoming antiquark
Need to fuse a quark and an antiquark each with
a kinetic energy of 40 GeV (equivalent to
half the W mass)
22
European Laboratory For Particle Physics
CERN
International laboratory near Geneva
FRANCE
SWITZERLAND
23
Collider

Inject anti- protons
RF cavities electric kick
Bending electro- magnet
Carlo Rubbia Antiprotons
Collide 2 beams Inside vacuum
Focusing electro- magnet
Simon van der Meer Stochastic cooling
Inject protons
24
CERN 71-25 Laboratory I Nuclear Physics
Division 26 November 1971
CERN 71-25
ORGANISATION EUROPÉENNE POUR LA RECHERCHE
NUCLÉAIRE CERN EUROPEAN ORGANIZATION FOR NUCLEAR
RESEARCH
LOWMOMENTUM ANTIPROTON PRODUCTION AT THE CERN
PROTON SYNCHROTRON
P. I. P. Kalmus, E. Eisenhandler, W. R. Gibson,
C. Hojvat L.C.Y. Lee Chi Kwong, T.W. Pritchard,
E.C. Usher and D.T. Williams Queen Mary College,
London M. Harrison and W. R. Range University of
Liverpool M. A. R. Kemp, A. D. Rush and J. N.
Woulds Daresbury Nuclear Physics Laboratory G.
T. J. Arnison, A. Astbury, D .P. Jones and
A.S.L.Parsons Rutherford High Energy Laboratory
25
(No Transcript)
26
W
around 1 in 108 collisions
Needle in a haystack !
e n
lots of particles
27
UA1 Experiment at CERN
Muon
Hadron
Vacuum
pipe
Wire
Proton
Antiproton
chamber
Electron
Hadron calorim.
Electromag
and magnet
calorimeter
Muon chambers
Neutrino
28
(No Transcript)
29
Finding the W
No other calorim. tracks 276
p p collisions 109
Angles match 167
Record on tape 975,000
No hadronic energy 72
Electron trigger 140,000
Energy matches mom. 39
High ET 28,000
Visual inspection
Hi. mom track 2,125
2 jet 23
electron jet 11
electron no jet 5
Points to calorim. 1,104
30
GeV
Missing energy flow
electron
direction
40
Events
20
with jets
40
20
20
40
E
normal
n
For each event, plot how much energy is missing,
and the direction relative to the electron in
which this flows
to electron
20
40
31
(No Transcript)
32
Carriers of Weak Force Found at CERN The W boson
the hypo
The Discovery of the W Boson The observation of
the W intermediate vector boson, the particle
that carries the weak nuclear force, is the most
outstanding achievement of the CERN laboratory in
Geneva and one of the most important advances in
physics of this century. It is the successful
conclusion of
carries the weak force which controls the
production of energy in the Sun and some
The Role of UK Scientists Twenty-five British
scientists played an important part in the
remarkable discovery of the W boson. They were
led by Professor J D Dowell of Birmingham
University, Professor P I P Kalmus of Queen Mary
College and Dr A Astbury of Rutherford Appleton
Laboratory. The W boson
33
It is very encouraging that so many British
scientists were in the team that discovered the
W boson, and I would like to congratulate you
and your colleagues from Queen Mary College on
your success. I am sure that British physicists
will be among the first to unify all the four
basic forces
From THE PRIME MINISTER 10 Downing
Street To Professor P. I. P. Kalmus
34
1982 Who are those people with Peter Kalmus ?
35
(No Transcript)
36
The End
p.i.p.kalmus_at_qmul.ac.uk
http//www.ph.qmul.ac.uk