9 The Standard Model of Fundamental Particles
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that so many different types of atom existed, and believed that perhaps atoms
themselves might be composed of something smaller. Rutherford’s experiments, described in Chap. 8, showed that atoms were indeed constructed of
neutrons, protons and electrons, and it was believed that at last the fundamental particles had been obtained. Everything of importance had been
learned, or so they maintained.
Perhaps this arrogance was an example of hubris, an offence in Greek
mythology that is a challenge to the gods, for it certainly brought a swift
retribution down on the heads of the perpetrators. Within a decade or two,
this cosy little clique of four fundamental particles (including the photon)
had to be expanded to include a plethora of new arrivals, some coloured and
flavoured, some charmed and others downright strange. (This may seem an
unusual collection of adjectives to associate with particles, but as we shall
see in later Sections, physicists working in this field love to choose curious
names.) So widespread had this influx become, rather like a horde of gatecrashers storming a dinner at the Athenaeum Club, that Willis Lamb joked
in his 1955 Nobel Lecture: “the finder of a new elementary particle used to be
rewarded by a Nobel Prize, but such a discovery now ought to be punished by a
10,000 dollar fine."
The term Particle Zoo was coined to describe the new state of affairs. As a
consequence of the random order in which the discovery of these new particles occurred, we will abandon here any attempt at chronology, and instead
arrange the particles post factum into groups depending on their nature.
9.3 The Four Forces
We saw in Chaps. 7 and 8 that two of the fundamental forces of nature,
gravity and electromagnetism, can be explained, the former by Einstein’s
theory of Relativity, and the latter by Quantum Electrodynamics. These
forces described all of the known physics up until the time Rutherford
and his co-workers upset the classical applecart with their discovery of the
atomic nucleus. Their experiments showed that these nuclei are comprised
of electrically charged protons and uncharged neutrons, both with masses
approximately 1837 times that of the electron.
The protons, being positively charged, experience a strong mutual electrostatic repulsion. Some new force must therefore be overpowering this
repulsion and holding the nucleus together. This force was given the somewhat unimaginative name, especially considering the flamboyant nomenclature prevalent today in particle physics, of strong nuclear interaction. The
167
that so many different types of atom existed, and believed that perhaps atoms
themselves might be composed of something smaller. Rutherford’s experiments, described in Chap. 8, showed that atoms were indeed constructed of
neutrons, protons and electrons, and it was believed that at last the fundamental particles had been obtained. Everything of importance had been
learned, or so they maintained.
Perhaps this arrogance was an example of hubris, an offence in Greek
mythology that is a challenge to the gods, for it certainly brought a swift
retribution down on the heads of the perpetrators. Within a decade or two,
this cosy little clique of four fundamental particles (including the photon)
had to be expanded to include a plethora of new arrivals, some coloured and
flavoured, some charmed and others downright strange. (This may seem an
unusual collection of adjectives to associate with particles, but as we shall
see in later Sections, physicists working in this field love to choose curious
names.) So widespread had this influx become, rather like a horde of gatecrashers storming a dinner at the Athenaeum Club, that Willis Lamb joked
in his 1955 Nobel Lecture: “the finder of a new elementary particle used to be
rewarded by a Nobel Prize, but such a discovery now ought to be punished by a
10,000 dollar fine."
The term Particle Zoo was coined to describe the new state of affairs. As a
consequence of the random order in which the discovery of these new particles occurred, we will abandon here any attempt at chronology, and instead
arrange the particles post factum into groups depending on their nature.
9.3 The Four Forces
We saw in Chaps. 7 and 8 that two of the fundamental forces of nature,
gravity and electromagnetism, can be explained, the former by Einstein’s
theory of Relativity, and the latter by Quantum Electrodynamics. These
forces described all of the known physics up until the time Rutherford
and his co-workers upset the classical applecart with their discovery of the
atomic nucleus. Their experiments showed that these nuclei are comprised
of electrically charged protons and uncharged neutrons, both with masses
approximately 1837 times that of the electron.
The protons, being positively charged, experience a strong mutual electrostatic repulsion. Some new force must therefore be overpowering this
repulsion and holding the nucleus together. This force was given the somewhat unimaginative name, especially considering the flamboyant nomenclature prevalent today in particle physics, of strong nuclear interaction. The