Cabibbo angle and quark mass spectrum

Abstract

It is proposed that the light quarks p, n, and lambda are massless when the weak interaction is switched off. Because of the mass degeneracy between the n and lambda fields the Cabibbo angle theta is undefined. When the weak interaction is switched on the light quarks manage to acquire masses by undergoing weak radiative processes involving heavy quarks (such as the charm quark), thus lifting the mass degeneracy. By identifying appropriate linear combinations of the n and lambda fields as the physical n and lambda states one in effect determines the Cabibbo angle. In this view, the orientation between the strong and weak interactions is controlled by the structure of the weak interaction. Strong interactions are assumed to be asymptotically free. The implementation of this program leads to a ''vector-like'' weak-interaction theory which involves six quarks and right-handed currents and which has been discussed on phenomenological grounds elsewhere. (One feature of this program is that the smallness of the neutral kaon mass difference is ensured without further adjustments.) The Cabibbo angle theta and the mass ratio m/subN//m/sub lambda/ (which measures the extent of chiral symmetry breaking) are thus fixed in terms of some of the other parameters appearing inmore » the theory, namely the mass ratio of the two positively charged heavy quarks and various mixing angles, for instance, the analog of theta in the right-handed current. These parameters are all measurable in principle. Our knowledge of theta and m/subN//m/sub lambda/ then enables various predictive statements to be made about these ratios and consequently the structure of the weak interaction at higher energies. This point of view also leads naturally to an intimate connection between zero theta and exact chiral SU(2) symmetry. (AIP)« less