Elementary particles and their interactions

The current standard model of physics is a result of the ongoing attempts to understand the structure of matter and its fundamental interaction. According to present knowledge, the elemental building blocks of matter consist of spin 1/2 fermions which interact with each other via the exchange of bosons. 

Presently we consider the quarks, which come in six different flavours, and the leptons, of which also six have been identified, as elementary fermions. 

The six quarks, namely the up quark (u), the down quark (d), the strange quark (s), the charm quark (c), the top quark (t), sometimes also called truth quark, and the bottom quark (b), also dubbed beauty quark, carry a colour charge. The bosons that act on colour, are called gluons, which are the carriers of the colour interaction. The residue of this interaction is the strong nuclear interaction, which is operative between the hadrons (for instance the proton and the neutron within an atomic nucleus). 

The electron (e), the muon (/i) and the tauon (r) are electric charge carrying members of the leptons, while their corresponding neutrinos and are electrically neutral. The charged leptons together with the quarks can interact with each other via exchange of a massless vector boson, the photon (7), which is the carrier of the electromagnetic interaction. 

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M. Gell-Mann (California Institute of Technology, Pasadena) contributions and discoveries concerning the classification of elementary particles and their interactions. 

NOTE On November 1982 a Solvay Conference devoted to Higher Energy Physics What are the possibilities for extending our understanding of elementary particles and their interactions to much greater energies was held in the University of Texas at Austin. 

For a first time the theme selected for the 8th Conference was Cosmic Ray and Nuclear Physics, but a long period of illness of the President of the Scientific Committee, Paul Langevin, imposed a first adjournment. Later it was decided that the conference would deal with the problems of elementary particles and their mutual interactions and that it would be held in October 1939. Even the list of speakers was prepared but World War II started on 3 September 1939 and the conference was postponed to an indefinite date. 

The atomic theory of matter, which was conjectured on qualitative empirical grounds as early as the sixth century BC, was shown to be consistent with increasing experimental and theoretical developments since the seventeenth century AD, and definitely proven by the quantitative explanation of the Brownian motion by Einstein and Perrin early in the twentieth century [1], It then took no more than a century between the first measurements of the electron properties in 1896 and of the proton properties in 1919 and the explosion of the number of so-called elementary particles - and their antiparticles - observed in modern accelerators to several hundred (most of which are very short lived and some, not even isolated). Today, the standard model assumes all particles to be built from three groups of four basic fermions - some endowed with exotic characteristics - interacting through four basic forces mediated by bosons - usually with zero charge and mass and with integer spin [2],... 

Obviously we may expect that the simple two- and three-particle collision approximation discussed in the previous sections is not appropriate, because a large number of particles always interact simultaneously. Formally this approximation leads to divergencies. In the previous sections we used in a systematic way cluster expansions for the two- and three-particle density operator in order to include two-particle bound states and their relevant interaction in three- and four-particle clusters. In the framework of that consideration we started with the elementary particles (e, p) and their interactions. The bound states turned out to be special states, and, especially, scattering states were dealt with in a consistent manner. 

In investigating the highly different phenomena in nature, scientists have always tried to find some fundamental principles that can explain the variety from a basic unity. Today they have shown not only that all the various kinds of matter are built up from a rather limited number of atoms but also that these atoms are composed of a few basic elements or building blocks. It seems possible to understand the innermost structure of matter and its behavior in terms of a few elementary particles electrons, protons, neutrons, photons, etc., and their interactions. Since these particles obey not the laws of classical physics but the rules of modem quantum theory of wave mechanics established in 1925, there has developed a new field of quantum science which deals with the explanation of nature on this basis. 

High-energy electrons are used in nuclear physics for the investigation of elementary and fundamental particles. Energies of the order of several GeV are sufficient to produce other elementary particles and antiparticles and to study their interactions. Collisions of electrons and positrons are investigated by use of storage rings. 

In the following, we comment on some peculiarities and restrictions of the slow coagulation theory since it can also be of importance for the adsorption kinetics. The elementary act of slow coagulation consists of the pairwise interaction of particles and their mutual diffusion as a nonsteady process. The concentration distribution of pairwise interacting particles is a function of distance and time and is described by the equation of non-steady electro-diffusion... 

The standard model of physics is based entirely on dimensionless point particles, and, whatever it may reveal about dark matter, it offers no explanation of the extension and structure of molecules. These elementary particles acquire their mass mathematically, on interaction with the hypothetical Higgs field, in a process of [2]... 

In physics and chemistry the elementary units composing the basic system are well known. These consist of elementary particles and photons or of composite units like atoms and molecules. The interactions between the units are also known there exist strong, electromagnetic, weak and gravitational interactions between elementary particles. More complex interactions like the interatomic forces responsible for chemical bonds and the van der Waals forces between molecules of a gas can be derived from these elementary interactions. The elementary units, their position and momentum vectors and their interactions constitute the basic microscopic level of a physico-chemical system. 

The phenomenon of attraction of masses is one of the most amazing features of nature, and it plays a fundamental role in the gravitational method. Everything that we are going to derive is based on the fact that each body attracts other. Clearly this indicates that a body generates a force, and this attraction is observed for extremely small particles, as well as very large ones, like planets. It is a universal phenomenon. At the same time, the Newtonian theory of attraction does not attempt to explain the mechanism of transmission of a force from one body to another. In the 17th century Newton discovered this phenomenon, and, moreover, he was able to describe the role of masses and distance between them that allows us to calculate the force of interaction of two particles. To formulate this law of attraction we suppose that particles occupy elementary volumes AF( ) and AF(p), and their position is characterized by points q and p, respectively, see Fig. 1.1a. It is important to emphasize that dimensions of these volumes are much smaller than the distance Lgp between points q and p. This is the most essential feature of elementary volumes or particles, and it explains why the points q and p can be chosen anywhere inside these bodies. Then, in accordance with Newton s law of attraction the particle around point q acts on the particle around point p with the force d ip) equal to... 

The brief review of the newest results in the theory of elementary chemical processes in the condensed phase given in this chapter shows that great progress has been achieved in this field during recent years, concerning the description of both the interaction of electrons with the polar medium and with the intramolecular vibrations and the interaction of the intramolecular vibrations and other reactive modes with each other and with the dissipative subsystem (thermal bath). The rapid development of the theory of the adiabatic reactions of the transfer of heavy particles with due account of the fluctuational character of the motion of the medium in the framework of both dynamic and stochastic approaches should be mentioned. The stochastic approach is described only briefly in this chapter. The number of papers in this field is so great that their detailed review would require a separate article. 

The magnitude of electric charge on an electron or proton that gives rise to their mutually attractive interaction. The charge on the elementary particles is referred to as elementary charge, is symbolized by e, and has a value of 1.60217733 X IQ- coulombs. 

Abstract. Investigation of P,T-parity nonconservation (PNC) phenomena is of fundamental importance for physics. Experiments to search for PNC effects have been performed on TIE and YbF molecules and are in progress for PbO and PbF molecules. For interpretation of molecular PNC experiments it is necessary to calculate those needed molecular properties which cannot be measured. In particular, electronic densities in heavy-atom cores are required for interpretation of the measured data in terms of the P,T-odd properties of elementary particles or P,T-odd interactions between them. Reliable calculations of the core properties (PNC effect, hyperfine structure etc., which are described by the operators heavily concentrated in atomic cores or on nuclei) usually require accurate accounting for both relativistic and correlation effects in heavy-atom systems. In this paper, some basic aspects of the experimental search for PNC effects in heavy-atom molecules and the computational methods used in their electronic structure calculations are discussed. The latter include the generalized relativistic effective core potential (GRECP) approach and the methods of nonvariational and variational one-center restoration of correct shapes of four-component spinors in atomic cores after a two-component GRECP calculation of a molecule. Their efficiency is illustrated with calculations of parameters of the effective P,T-odd spin-rotational Hamiltonians in the molecules PbF, HgF, YbF, BaF, TIF, and PbO. 

The accurate quantum mechanical first-principles description of all interactions within a transition-metal cluster represented as a collection of electrons and atomic nuclei is a prerequisite for understanding and predicting such properties. The standard semi-classical theory of the quantum mechanics of electrons and atomic nuclei interacting via electromagnetic waves, i.e., described by Maxwell electrodynamics, turns out to be the theory sufficient to describe all such interactions (21). In semi-classical theory, the motion of the elementary particles of chemistry, i.e., of electrons and nuclei, is described quantum mechanically, while their electromagnetic interactions are described by classical electric and magnetic fields, E and B, often represented in terms of the non-redundant four components of the 4-potential, namely the scalar potential and the vector potential A. 

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