Quantum Chromodynamics

Within the philosophy of science there has been a great deal of rather vague talk about the 'heuristic fruitfulness' (or what Peirce called the 'esperable uberty') of theories. It is my aim in the present paper to add some precision to these discussions by linking this 'fruitfulness' to the satisfaction of certain heuristic criteria. In this manner the demarcation between 'discovery' and 'pursuit' becomes blurred. As a case study, I present the competition between the paraparticle and colour models of quarks (...) in the late 1960s. I argue that the eventual appraisal of the latter as the more fruitful of the two was based on the incorporation of a particular symmetry principle, regarded as a heuristic guideline, rather than on non-epistemic factors concerning 'cognitive resources' and the like. (shrink)

Values of some arbitrary parameters appearing in a geometrical model for elementary particles developed by MacGregor are compared with quantities associated with classical properties of blocks of charges±e interacting via Coulomb forces and hard-sphere repulsion only. If it is assumed that masses and radii of individual charged particles are related bymc 2=(2/3)(e 2/r) and thatmc 2=6.87 MeV, then the self-energiesM andM ± of 24-particle neutral blocks and 25-particle charged blocks composed of layers of three octagons and of a square sandwiched (...) by two distorted octagons satisfyM=70.1 MeV,M ±=74.2 MeV. The binding energyB nn of pairs of neutral blocks is given byB nn=4.9 MeV, and the maximum radius of the neutral block is 0.60 F. These four calculated parameter values lie within an average of 1% of the corresponding quantities for nonspinning quarks determined empirically by MacGregor. (shrink)

Partons (quarks) are unobservable, it is suggested, because they have no well-defined rest-massconcept.

In this paper, we wish to outline the main historical moments which have led to the first exact measurements of the anomalous magnetic moment of the muon.