Abstract
The CERN control centre resembles those of space missions: a huge room with scores of desks and monitors, small ones on consoles and large ones mounted on walls, displaying real time images, data and plots representing the operation of the various machines. The building is immersed in green foliage on a small road, Route André Lagarrigue. This French physicist is unknown to the general public, but he was at the origin of the first major CERN discovery, so-called ‘neutral currents’, which opened the way to unification of forces.
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Notes
- 1.
By definition the hadron containing an \( \overline{s} \)-antiquark and a d-quark is called a ‘kaon’ so that the one containing an s-quark is an ‘antikaon’.
- 2.
Independently of Murray Gell-Mann, in 1964 George Zweig, a 27 year old American physicist born in Moscow, proposed a similar model of hadrons made of smaller constituents which he called ‘aces’ because he thought there were four of them.
- 3.
The baryons Λ 0 and Σ 0, which have the same quark structure uds, are different particles because the wavicles of the three quarks have different spatial distributions.
- 4.
Making use of the charges of the quarks listed in Table 4.1, it is easy to check the charge of the two composite systems: \( {\varXi}^{-} = \mathrm{d}\mathrm{s}\mathrm{s} = -\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$3$}\right.-\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$3$}\right.-\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$3$}\right. = -1 \); \( {\varXi}^0 = \mathrm{u}\mathrm{s}\mathrm{s}=\raisebox{1ex}{$2$}\!\left/ \!\raisebox{-1ex}{$3$}\right.-\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$3$}\right.-\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$3$}\right. = 0 \).
- 5.
In the case of the electric force this does not happen; a negative electron remains a negative electron after emitting a virtual photon, which is electrically neutral.
- 6.
The strong force, as well as binding the quarks, ‘spills over’ from the protons and neutrons holding them together in nuclei with a secondary force called the ‘nuclear binding force’. It is this residual force which permits the existence of atomic nuclei, made of many protons and neutrons and therefore of the matter which makes up our bodies and every object in the world around us.
- 7.
The three neutrinos have such small masses that in Fig. 4.6 only experimental upper limits are reported (the symbol < means ‘less than’). These insubstantial matter-particles do not have sufficient energy to decay into other particles, therefore they are stable; once produced, for example immediately after the Big Bang, neutrinos live for ever, moving almost at the speed of light and interacting very little with matter.
- 8.
In nuclear fusion of hydrogen, 2 of the initial 4 protons undergo the inverse process to the one shown in Fig. 4.7 from the effect of the weak force; each proton is transformed into a neutron, a positron and a neutrino. In this way a helium nucleus, composed of 2 protons and 2 neutrons, is produced.
- 9.
Pauli called the hypothetical neutral particle the ‘neutron’, but with the discovery in 1930 of the neutron, which is an essential component of all atomic nuclei, this nomenclature created much confusion. For this reason in 1933 Enrico Fermi began to refer to the new particle as ‘neutrino’, following an exchange in via Panisperna when Edoardo Amaldi – Fermi having explained that Pauli’s neutron was not the one from nuclei because it had a much smaller mass – said without too much thought: “But then that is not a neutron, it’s a neutrino”. (In Italian the diminutive is expressed by applying the suffix –ino to a noun.)
- 10.
The first observation was due to the American physicist Raymond Davis, who applied the Pontecorvo chlorine method (figure 4.10b) and was awarded the 2002 Nobel Prize for the experimental detection of solar neutrinos.
- 11.
Since in Italian it is easy to invent diminutives, augmentatives and pejoratives by using modifying suffixes, I dare to suggest for the three neutrinos a new, compact and meaningful nomenclature: neutrino, neutretto and neutrotto (‘fatter neutrino’) are certainly better than electron-neutrino, muon-neutrino and tau-neutrino in conveying the fact that they refer to neutral particles of very small and increasing masses.
- 12.
The more than 50 physicists who signed the discovery paper came from – as well as the Orsay Laboratory in France and from CERN – the Paris École Polytechnique, University College London and the universities of Aachen, Brussels and Milan.
References
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Amaldi, U. (2015). Force-Particles and Matter-Particles. In: Particle Accelerators: From Big Bang Physics to Hadron Therapy. Springer, Cham. https://doi.org/10.1007/978-3-319-08870-9_4
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