Vacuum expectation value. In quantum theory, the magnitudes of observable quantities such as energy are given as the so-called expectation (or average) values of quantum-mechanical operators which correspond to the observables. The operators are mathematical functions which operate on, and change, the wavefunctions. The vacuum expectation value is the expectation value of the operator in a vacuum. Because of the shape of the potential energy curve of the Higgs field, it has a non-zero vacuum expectation value which breaks the symmetry of the electro-weak force – see Figure 13, p. 87.
W, Z particles. Elementary particles which carry the weak nuclear force. The W particles are spin 1 bosons with unit positive and negative electrical charge (W+, W−) and masses of 80 GeV. The Z0 is an electrically neutral spin 1 boson with mass 91 GeV. The W and Z particles gain mass through the Higgs mechanism and can be thought of as ‘heavy’ photons.
Wave–particle duality. A fundamental property of all quantum particles, which exhibit both delocalized wave behaviour (such as diffraction and interference) and localized particle behaviour depending on the type of apparatus used to make measurements on them. First suggested as a property of matter particles such as electrons by Louis de Broglie in 1923.
Wavefunction. The mathematical description of matter particles such as electrons as ‘matter waves’ leads to equations characteristic of wave motion. Such wave equations feature a wavefunction whose amplitude and phase evolve in space and time. The wavefunctions of the electron in a hydrogen atom form characteristic three-dimensional patterns around the nucleus called orbitals. Wave mechanics – an expression of quantum mechanics in terms of matter waves – was first elucidated by Erwin Schrödinger in 1926.
Weak neutral current. A weak-force interaction involving the exchange of a virtual Z0 boson or a combination of virtual W+ and W− particles, see Figures 15 and 16, pp. 100 and 127.
Weak nuclear force. The weak force is so called because it is considerably weaker than both the strong and electromagnetic forces, in strength and range. The weak force affects both quarks and leptons and weak-force interactions can change quark and lepton flavour, for example turning an up-quark into a down-quark and an electron into an electron neutrino. The weak force was originally identified as a fundamental force from studies of beta-radioactive decay. Carriers of the weak force are the W and Z particles. The weak force was combined with electromagnetism in the SU(2)×U(1) quantum field theory of the electro-weak force by Steven Weinberg and Abdus Salam in 1967–68.
Yang–Mills field theory. A form of quantum field theory based on gauge invariance developed in 1954 by Chen Ning Yang and Robert Mills. Yang–Mills field theory underpins all the components of the current Standard Model of particle physics.
BIBLIOGRAPHY
Baggott, Jim, Beyond Measure: Modern Physics, Philosophy and the Meaning of Quantum Theory, Oxford University Press, 2003.
Baggott, Jim, The Quantum Story: A History in 40 Moments, Oxford University Press, 2011.
Cashmore, Roger, Maiani, Luciano, and Revol, Jean-Pierre (eds.), Prestigious Discoveries at CERN, Springer, Berlin, 2004.
Crease, Robert P. and Mann, Charles C., The Second Creation: Makers of the Revolution in Twentieth-Century Physics, Rutgers University Press, 1986.
Dodd, J.E., The Ideas of Particle Physics, Cambridge University Press, 1984.
Enz, Charles P., No Time to be Brief: a Scientific Biography of Wolfgang Pauli, Oxford University Press, 2002.
Evans, Lyndon (ed.), The Large Madron Collider: A Marvel of Technology, CRC Press London, 2009.
Farmelo, Graham (ed.), It Must be Beautiful: Great Equations of Modern Science, Granta Books, London, 2002.
Feynman, Richard P., QED: The Strange Theory of Light and Matter, Penguin, London, 1985.
Gell-Mann, Murray, The Quark and the Jaguar, Little, Brown & Co., London, 1994.
Gleick, James, Genius: Richard Feynman and Modern Physics, Little, Brown & Co., London, 1992.
Greene, Brian, The Elegant Universe: Superstrings, Hidden Dimensions and the Quest for the Ultimate Theory, Vintage Books, London, 2000.
Greene, Brian, The Fabric of the Cosmos: Space, Time and the Texture of Reality, Allen Lane, London, 2004.
Gribbin, John, Q is for Quantum: Particle Physics from A to Z, Weidenfeld & Nicholson, London, 1998.
Guth, Alan H., The Inflationary Universe: The Quest for a New Theory of Cosmic Origins, Vintage, London, 1998.
Halpern, Paul, Collider: The Search for the World’s Smallest Particles, John Wiley, New Jersey, 2009.
Hoddeson, Lillian, Brown, Laurie, Riordan, Michael, and Dresden, Max, The Rise of the Standard Model: Particle Physics in the 1960s and 1970s, Cambridge University Press, 1997.
Johnson, George, Strange Beauty: Murray Gell-Mann and the Revolution in Twentieth-Century Physics, Vintage, London, 2001.
Kane, Gordon, Supersymmetry: Unveiling the Ultimate Laws of the Universe, Perseus Books, Cambridge, MA, 2000.
Kragh, Helge, Quantum Generations: A History of Physics in the Twentieth Century, Princeton University Press, 1999.
Lederman, Leon (with Dick Teresi), The God Particle: If the Universe is the Answer, What is the Question?, Bantam Press, London, 1993.
Mehra, Jagdish, The Beat of a Different Drum: The Life and Science of Richard Feynman, Oxford University Press, 1994.
Nambu, Yoichiro, Quarks, World Scientific, Singapore, 1981.
Pais, Abraham, Subtle is the Lord: The Science and the Life of Albert Einstein, Oxford University Press, 1982.
Pais, Abraham, Inward Bound: Of Matter and Forces in the Physical World, Oxford University Press, 1986.
Pickering, Andrew, Constructing Quarks: A Sociological History of Particle Physics, University of Chicago Press, 1984.
Riordan, Michael, The Hunting of the Quark: A True Story of Modern Physics, Simon & Shuster, New York, 1987.
Sambursky, S., The Physical World of the Greeks, 2nd Edition, Routledge & Kegan Paul, London, 1963
Sample, Ian, Massive: The Hunt for the God Particle, Virgin Books, London, 2010.
Schweber, Silvan S., QED and the Men Who Made It: Dyson, Feynman, Schwinger, Tomonaga, Princeton University Press, 1994.
Stachel, John (ed.), Einstein’s Miraculous Year: Five Papers that Changed the Face of Physics, Princeton University Press, 2005.
’t Hooft, Gerard, In Search of the Ultimate Building Blocks, Cambridge University Press, 1997.
Veltman, Martinus, Facts and Mysteries in Elementary Particle Physics, World Scientific, London, 2003.
Weinberg, Steven, Dreams of a Final Theory: The Search for the Fundamental Laws of Nature, Vintage, London, 1993.
Weyl, Hermann, Symmetry, Princeton University Press, 1952.
Wilczek, Frank, The Lightness of Being: Big Questions, Real Answers, Allen Lane, London, 2009
Woit, Peter, Not Even Wrong, Vintage Books, London, 2007.
Zee, A., Fearful Symmetry: The Search for Beauty in Modern Physics, Princeton University Press, 2007 (first published 1986).
INDEX
‘aces’ (Zweig’s quark equivalents) 83, 84
Adler, Stephen 110
Alvarez, Luis 70
Anderson, Carl 56
Anderson, Philip xix, 84–5
angular momentum conservation 21, 30
invariant to rotational symmetry transformation 26
anti-matter 8, 38
anti-quarks 80
anti-bottom quarks 142
anti-charm quarks 141
anti-neutrinos 60, 151, 203
anti-protons:
concentrating energies of 147–8 see also proton–anti-proton colliders
Arab-Israeli war 70
Arosa, Switzerland 31, 33
Aspen Center for Physics, Colorado 108, 109, 137
asymptotic freedom 135–7
atom bomb 12, 40, 41, 119
atomic nucleus 4, 9, 10, 220 see also strong force
atomic orbitals 5, 9, 220
atomic structure:
Bohr’s quantum model 31–2
‘planetary model’ 4–5
atoms 9, 220
Ancient Greek conception 2
forces within 13–15
transmutability 11
Austin Chalk, Texas 163–4
Avogadro’s number 11
‘B’ field 50
‘B’ particles 50–1
Bacon, Francis 59
bar magnets 135n
Bardeen, John 74, 109
Bardeen, William 109–10, 110n
‘barns’ (units of measurement) 194
baryons 64–5, 112
behaving like bosons 97
‘charmed’ 102
Eightfold Way octet 68–9, 78
quark composition 80, 110
Berkeley 70, 92
Berkeley Radiation Laboratory 120
Berners-Lee, Tim 170
beta-radioactive decay 13, 15, 47, 58
Fermi’s theory 54–5, 60
quark model 81
Schwinger’s model 60–1
Bethe, Hans 41, 42–3, 44
Bevatron 120
big bang 154, 155, 156, 158
lambda-CDM model 105n, 183
‘big science’ 119, 163, 165
Bjorken, James 122–3, 125
Block, Richard 68
Bohm, David 41
Bohr, Niels 31
Bose, Satyendra Nath 65
bosinos 182
bosons 65
and supersymmetry 181–2
bottom quarks 142, 176, 186
bottom/anti-bottom pairs 142, 178
Higgs boson decay channels 178
mass 142, 177
Boxer Indemnity 46, 46n
Brahe, Tycho 19
Brookhaven National Laboratory 49, 140, 141
Alternating Gradient Synchrotron (AGS) 120, 140
Cosmotron 120
ISABELLE 159
Brout, Robert xv, 85, 90, 158, 207n
bubble chambers 128
Bush, George 163, 164–5, 166
Butterworth, John 198–9, 211
California Institute of Technology (Caltech) 62, 64, 68, 83, 109, 137
Campaign for Nuclear Disarmament 90
Casper, Dave (the ‘Ghost’) 161
CERN (Organisation Européenne pour la Recherche Nucléaire) xiv, xv, 71, 83, 84, 98, 105, 109, 125, 147–8, 149, 162, 181, 190-1, 193-6, 200-2, 209-10, 214-5, 217, 219
‘blockbuster’ announcement procedure 201
discovery of W and Z particles 151–2
establishment 120
funding 168, 169, 170, 176, 176n
Gargamelle bubble chamber 129–30, 131n, 133
Intersecting Storage Rings (ISR) 145, 146, 148
search for W and Z particles 149–51
search for weak neutral currents 129–34
Super Proton Synchrotron (SPS) 120, 129, 144, 145, 146, 150–1, 200
Underground Area 1 (UA1) 150, 151–2
Underground Area 2 (UA2) 150, 151–2
CERN Large Electron-Positron Collider (LEP) 145, 146, 159–60, 178–80, 177, 196
Aleph detector 178, 178n, 197
Delphi detector 178–9, 179n
L3 detector 179
CERN Large Hadron Collider (LHC) xiii, 168, 179, 185–90, 191–2, 194-5, 197, 200-1, 205, 208-15, 221
A Large Ion Collider Experiment (ALICE) 186
A Toroidal LHC Apparatus (ATLAS) 186–7, 189, 191–2, 196–9, 201–7, 209, 210, 213-4, 216-8
Compact Muon Solenoid (CMS) 186, 187–8, 189, 191–2, 199, 201, 202, 205–7, 209, 210, 213-8
discovery of Higgs boson xi, 215–9
Large Hadron Collider beauty (LHCb) 186
Large Hadron Collider forward (LHCf) 186
performance/luminosity achievements 200, 201, 205, 209, 213
problems (2008) 190
re-start (November 2009) 191
search for Higgs boson 191–3, 197, 200–7, 210, 211, 219
switching on (September 2008) 190
TOTal Elastic and diffractive cross-section Measurement (TOTEM) 186
Chadwick, James 9, 40
charm quarks 134, 142
charm/anti-charm quark pairs 141
discovery 141
proposal 99, 101, 102, 126
search for 140–1
Chicago University 46, 64, 73
Cline, David 130, 131–2, 133, 134
Clinton, Bill 166
cloud chambers 128
Cockcroft, John 118
Cold War 120
colour charge 110–12, 110n, 137, 220–1
‘masking’ 138–9
colour force see strong nuclear force
Columbia University 55, 64, 78, 92, 196
Coma Cluster 183
Communist East Germany 108–9
complex numbers 32, 32n
complex planes 33
conservation laws 20–1
and continuous symmetry transformation 23, 24–7, 30
Cooper, Leon 74
Cornell University 61, 92
Cosmic Background Explorer (COBE) satellite 158
cosmic rays 9, 56–8
and high-energy particles 117, 117n
cosmological constant 105n
cosmology 154–8, 183
Cox, Brian 176n
cyclotrons 118–19
‘dark energy’ 183
‘dark matter’ 183, 186
Darriulat, Pierre 146, 150
Dayan, Moshe 70–1
de Broglie, Louis 32, 33, 35
‘deep inelastic’ scattering 122–3, 124, 125, 135
Democritus 2, 165
Desertron 160 see also Superconducting Supercollider
Di Lella, Luigi 152
di-photon mass distribution 197, 198, 200, 217
Dirac, Paul 5, 38
relativistic quantum theory 5–9, 38, 41
Dorigo, Tommaso 192, 193, 211, 215
down quarks 80, 81, 96, 97, 99, 110, 111, 141, 176, 220–1
mass 139
Dukas, Helen 196
Dyson, Freeman 44, 91
E=mc2 12, 12n
Eidgenossische Technische Hochschule (ETH) 29
Eightfold Way 68–70, 71, 97, 102, 107
missing fundamental particles 78–80
Einstein, Albert 30, 36, 37, 41, 139, 205
cosmological constant (‘fudge factor’) 105n
equivalence principle 103–4
general theory of relativity 20, 29
simple explanation of relativity 196
special theory of relativity 5, 11–12, 38, 43, 88n
and Weyl’s gauge theory 30–1
‘elastic’ scattering 121
electric charge 48
and Eightfold Way classification 69
electric charge conservation 27
and phase symmetry of electron wavefunction 33, 45
search for continuous symmetry transformation 28–30
and superconductivity 74–5
electromagnetism 14–15, 135
convergence with strong and weak forces in MSSM 182–3
Maxwell’s equations 27–8, 30, 38
need for quantum field description 38–9
parallels with weak nuclear force 55, 60
post-big bang division from weak force 154
symmetry-breaking 75–6
unification with gravity 30 see also electro-weak field theory; quantum electrodynamics
electron-neutrinos 141
electron-positron annihilation 142
electron-positron collisions 140–1, 145, 178
electron-positron pairs 140, 152
electron-proton collisions 121–3
electron spin 5–7, 8, 38
paired 8, 9, 220
spin-up and spin-down 7, 9, 220
electron wavefunction 5, 8, 32–3, 96
changes compensated in electromagnetic field 50
and electric charge conservation 33, 45
electrons 9, 12, 65, 141, 178
, 220
angular momentum 8
beta particles 13, 47, 55, 60
Cooper pairs 74, 75–6
discovery 4
division from quarks and neutrinos 155
electric charge measurement 79, 79n
exchange of photons in QED 14–15
g-factor 41, 45
mass, ratio to proton 57, 57n
Pauli exclusion principle 7–8, 96, 97
planetary model 4–5
quantized orbits 31
self-interaction 39–40, 42
as signals of W- particle decay 151
volt measure 47n
wave/particle duality 5, 32, 35
‘electro-nuclear force’ 155
convergence of forces predicted by MSSM 182–3
grand unified theory 155–6
SU(3)×SU(2)×U(1) field theory 112, 138, 181
symmetry-breaking 155, 158
‘electro-weak epoch’ 154
electro-weak field theory (SU(2)×U (1)) xv, 62–3, 67, 91, 98–102
experimental validation 153
of leptons 93–4, 98, 101
massless particles problem 63, 91
massless particles problem solved by application of Higgs mechanism 92–3, 94, 101, 107, 126, 153, 158, 171
renormalization problem 63, 93, 94, 95, 98, 102, 103
renormalizability proved 106–7, 153
weak neutral currents problem 63, 93, 94, 98–9
weak neutral current problem solved 99–102, 126
elements 9, 220
‘classical’ 1, 2
Empedocles 1
energy:
balance, in beta-radioactivity 13
conservation 20, 25–6, 30
and matter 12, 20
Englert, François xv, 85, 90, 158, 207, 214
equivalence principle 103–4
eta mesons:
discovery 70
European Physical Society (EPS) physics conference, 2011 202–5
Evans, Lyndon 190, 201
facial symmetry 23
Faraday, Michael 27
Fermi, Enrico 40, 44, 46, 54–5, 58, 60, 64, 65
beta-radioactivity theory 54–5, 60
Fermi National Accelerator Laboratory (Fermilab), Chicago (previously National Accelerator Laboratory) xiv, xv, 130n, 142, 144, 149, 150, 163, 176, 177, 195, 214
Higgs boson discovery rumour 192–3
Tevatron 145–6, 149, 159, 160, 177, 191, 192–3, 194, 195, 214
Higgs:The invention and discovery of the 'God Particle' Page 21