The book “Leptons and Quarks” was first published in the early 1980s, when the program of the experimental search for the intermediate bosons W and Z and Higgs boson H was formulated. The aim and scope of the present extended edition of the book, written after the experimental discovery of the Higgs boson in 2012, is to reflect the various stages of this 30+ years search. Along with the text of the first edition of “Leptons and Quarks” it contains extracts from a number of books published by World Scientific and an article from “On the concepts of vacuum and mass and the search for higgs” available from http://www.worldscientific.com/worldscinet/mpla or from http://arxiv.org/abs/1212.1031.
The book is unique in communicating the Electroweak Theory at a basic level and in connecting the concept of Lorenz invariant mass with the concept of the Extended Standard Model, which includes gravitons as the carriers of gravitational interaction.
Contents:
Introduction
Structure of Weak Currents
Muon decay
Strangeness-Conserving Leptonic Decays of Hadrons. Properties of the Ud-Current
Leptonic Decays of Pions and Nucleons
Leptonic Decays of K-Mesons and Hyperons
Strangeness-Changing Non-Leptonic Interactions
Phenomenology of Non-Leptonic Interactions
Dynamics of Non-Leptonic Decays of Hyperons
Non-Leptonic Decays of K-Mesons
Neutral K-Mesons in Vacuum and in Matter
Violation of CP Invariance
Decays of the τ-Lepton
Decays of Charmed Particles
Weak Decays b- and t-Quarks
Neutrino–Electron Interactions
Neutrino–Nucleon Interactions
Renormalizability
Gauge Invariance
Spontaneous Symmetry Breaking
Standard Model of the Electroweak Interaction
Neutral Currents
Properties of Intermediate Bosons
Properties of Higgs Bosons
Grand Unification
Superunification
Particles and the Universe
Bibliography
Apendix (Some Useful Formulas)
Tables of Experimental Data
Readership: Graduate students and researchers in high energy and particle physics.
The weak interaction is responsible for a large number of physical processes: nuclear ÎČ-decay, numerous decays of elementary particles, reactions induced by neutrinos from accelerators and nuclear reactors, and also some subtle effects involving parity violation in Îł-decays of nuclei and in atomic optical spectra. All known leptons and hadrons are subject to the weak interaction. It plays an important role in such astrophysical phenomena as the sunâs burning and supernova explosions. Some of the weak processes were already put to use (for example, the angular asymmetry in the muon decay is a promising new tool in chemistry). Mainly, however, our interest in the weak interaction is rooted not in its possible applications but in the hope that its study will ultimately yield a unified theory of elementary particles and of the interactions between them. And although it would be very difficult today to predict any practical consequences of such a unified theory, there can be no doubt of their utmost importance.
In contrast to âstrongerâ interactions, namely the strong and electromagnetic, the weak interaction violates a number of conservation laws. Among the quantum numbers that are not conserved are space parity P, charge conjugation parity C, combined inversion parity CP, strangeness, charm, and some others.
The standard theory of weak interactions is based on the analogy with the electromagnetic interaction which is produced by the electromagnetic current coupled to the photon (see fig. 1.1). Likewise, the weak interaction is postulated to result from weak currents being coupled to the so-called intermediate bosons W+, Wâ, Z. Intermediate bosons have not yet been found experimentally; however, this does not point to a defect in the theory since the expected masses are of the order of 100 GeV, the energies of the existing accelerators being well below their production thresholds. The W+ and Wâ bosons are coupled to charged currents which change the charges of particles involved. Such are the currents
and their hermitian conjugate currents
The last two currents, for instance, interact by exchanging a virtual W-boson and yield the muon decay
(fig. 1.2). The Z0 bosons are created by neutral currents of the types
and so on, involving identical ingoing and outgoing particles. Neutral currents are responsible, for example, for the scattering vÎŒe â vÎŒe (fig. 1.3). Both the charged and the neutral currents include a leptonic and a hadronic part. At present we know six leptons which are naturally grouped into three pairs:
Fig. 1.1.
so that each lepton has its neutrino counterpart. Each lepton enters the charged current j with the appropriate neutrino:
This current emits W+ bosons and absorbs Wâ bosons. The hermitian conjugate current
emits Wâ bosons and absorbs W+ bosons. The neutral leptonic current
contains six terms:
The two leptonic currents given above are responsible for the processes involving both leptons
and antileptons
This follows from the properties of the relevant operators. For example, the operator Ä creates an electron and annihilates a positron, while the operator e creates a positron and annihilates an electron. Operators of other particles act in a similar manner.
Fig. 1.2.
Fig. 1.3.
1.1. Quark currents
Hadrons are represented in weak currents by quarks. According to quark theory, all known hadrons consist of quarks of five types (five flavors): u, d, s, c and b. Theoretical arguments, however, point to the existence of a sixth quark t, so that in analogy to the six leptons, the six quarks form three pairs:
We recall that the charges of quarks u, c, and t are
and those of quarks d, s, and b are
The quark structure is uud for the proton, udd for the neutron,
for the Ï+ meson, and so on. Strange particles include s-quarks (for instance,
), and charmed particles include c-quarks (for example,
). Particles with hidden charm, such as the J/Ï meson, are represented by
The structure of the T-meson is
No hadrons with single b-quarks have so far been found*, and only very scant indirect information is available on the weak interaction of the b- and t-quarks (se...
