Higgs

7. There Must Be Ws

Matter Particles

Force Particles

Epilogue: The Construction of Mass

The discovery of a new particle at CERN suggests strongly that the quark masses are derived from interactions with the Higgs field. These interactions transform otherwise massless quarks into particles with mass. The interactions give the particles depth, causing them to slow down. This resistance to acceleration is what we call mass.

Glossary

Baryon, p 231

From the Greek barys, meaning heavy. Baryons form a subset of hadrons. They are heavier particles which experience the strong nuclear force and include the proton and neutron. They are composed of triplets of quarks.

Boson, p 232

Named for India physicist Satyendra Nath Bose. Bosons are characterized by integral spin quantum numbers (1, 2,..., etc.) and, as such, not subject to Pauli's exclusion principle. Bosons are involved in the transmission of forces between matter particles, and include the photon (electromagnetism), the W and Z particles (weak force), and gluons (colour force). Particles with spin zero are also called bosons but these are not involved in transmitting forces. Examples include the pions, Cooper pairs (which can also have spin 1), and the Higgs boson. The graviton, the hypothetical particle of the gravitational field, is believed to be a boson of spin 2.

Fermion, p 238

Named for Italian physicist Enrico Fermi. Fermions are characterized by half-integral spins (1/2, 3/2, etc.) and include quarks and leptons and many composite particles produced from various combinations of quarks, such as baryons.

Gluon, p 240

The carrier of the strong colour force between quarks. Quantum chromodynamics require eight, massless colour force gluons which themselves carry colour charge. Consequently, the gluons participate in the force rather than simply transmit it from one particle to another. Ninety-nine per cent of the mass of protons and neutrons is thought to be energy carried by gluons.

Hadron, p 241

From the Greek hadros, meaning thick or heavy. Hadrons form a class of particles which experience the strong nuclear force and are therefore composed of various combinations of quarks. This class includes baryons, which are composed of three quarks and mesons, which are composed of one quark and an anti-quark.

Kaon, p 242

A group of spin-0 mesons consisting of up-, down-, and strange-quarks and their anti-quarks. These are K⁺ (up-anti-strange), K^- (strange-anti-up), and K⁰ (mixture of down-anti-strange and strange-anti-down) with masses 494 MeV (K^±) and 498 MeV (K⁰).

Lepton, p 243

From the Greek leptos, meaning small. Leptons form a class of particles which do not experience the strong nuclear force and combine with quarks to form matter. Like quarks, leptons form three generations, including the electron, muon, and tau, with electric charge -1, spin 1/2, and masses 0.51 MeV, 106 Mev, and 1.78 Gev, respectively, and their corresponding neutrinos. The electron, muon, and tau neutrinos carry no electric charge, have spin 1/2, and are believed to possess very small masses (necessary to explain the phenomenon of neutrino oscillation, the quantum-mechanical mixing of neutrino flavours such that the flavour may change over time).

Meson, p 244

From the Greek mésos, meaning 'middle'. Mesons are a sub-set of hadrons. They experience the strong nuclear force and are composed of quarks and anti-quarks.

Muon, p 244

A second-generation lepton equivalent to the electron, with a charge -1, a spin 1/2 (fermion), and mass 106 Mev. First discovered in 1936 by Carl Andersson and Seth Neddermeyer.

Neutrino, p 245

From Italian, meaning 'small neutral one'. Neutrinos are the chargeless, spin 1/2 (fermion) companions to the negatively charged electron, muon, and tau. The neutrinos are believed to possess very small masses, necessary to explain the phenomenon of neutrino oscillation, the quantum-mechanical mixing of neutrino flavours such that the flavour may change over time. Neutrino oscillation solves the solar neutrino problem — that the numbers of neutrinos measured to pass through the earth are inconsistent with the numbers of electron neutrinos expected from nuclear reactions occurring in the sun's core. It was determined in 2001 that only 35 per cent of the neutrinos from the sun are electron neutrinos — the balance are muon and tau neutrinos, indicating that the neutrino flavours oscillate as they travel from the sun to the earth.

Pion, p 247

A group of spin-0 mesons formed from up- and down-quarks and their anti-quarks. These are π⁺ (up-anti-down), π^- (down-anti-up), and π⁰ (a mixture of up-anti-up and down-anti-down), with masses 140 MeV (π^±) and 135 MeV (π⁰).

Quark, p 249

The elementary consistuents of hadrons. All hadrons are composed of triplets of spin 1/2 quarks (baryons) or combinations of quarks and anti-quarks (mesons). The quarks form three generations, each with different flavours. The up- and down-quarks, with electric charges +2/3 and -1/3 and masses of 1.7-3.3 MeV and 4.1-5.8 MeV, respectively, form the first generation. Protons and neutrons are composed of up- and down-quarks. The second generation consists of the charm and strange-quarks, with electric charges +2/3 and -1/3 and masses of 1.27 GeV and 101 MeV, respectively. The third generation consists of bottom and top quarks, with electric charges +2/3 and -1/3 and masses of 4.19 GeV and 172 GeV, respectively. Quarks also carry colour charge, with each flavour of quark possessing red, green, or blue charges.