5 Search Results

Here we examine the medium strong mass splittings for pseudo-scalar mesons, vector mesons and spin-2/3 baryons in the framework of the «fifth interaction» proposed by Ne’eman. In addition to the resonance contributions from the low-lying states, we write an expression for the contribution from f₈ Regge exchange in terms of contributions to electromagnetic mass differences from $$\text{A}^0_2$$ Regge exchange. Assuming that the $$\text{A}^0_2$$ Regge pole gives the correct contribution to the e.m. mass differences, we estimate the contribution of the f₈-meson. In the approximation of neglecting the continuum spectrum, the ratio of tadpole contributions is given by the ratio ofmore » coupling constants of the f₈-meson with hadrons. The results of the tadpole model are in agreement with the subtraction scheme of Segrè. We also find that in the presence of such anSU₃-symmetry-breaking term, the renormalization of the hadronic weak-strangeness-changing vector current vertex, to second order in such a term, is quadratically divergent.« less

Momentum-transfer-dependent damping of the nucleon form factors due to the virtual exchange of soft nonchiral pseudoscalar-pion pairs is estimated. When chirality is enforced, by embedding the calculation in the nonlinear $$σ$$ model, these soft effects are shown to cancel to all orders in the strong coupling. Finally, by themselves, the contributions described here do not easily fit the experimental data.

Using asymptotic SU(3) and superconvergence relations, the ω-φ mixing angle is determined and mass formulas for pseudoscalar and vector mesons are derived.

The πω problem, as the simplest case of the pseudoscalar-meson and vector-meson system, is discussed from the standpoint of the S-matrix approach. A general procedure of constructing invariant amplitudes in spin and isospin space of the pseudoscalar-vector system is given, and for πω scattering, a set of invariant amplitudes are conveniently chosen and their crossing properties are discussed. These amplitudes are expressed by one-dimensional representations which are derived from the Mandelstam representations by the Cini-Fubini technique. Partial-wave expansions as well as projections are done by the use of the Jacob-Wick helicity amplitudes. A prescription for calculating the driving forces frommore » the exchange of particles is presented and applied to the exchange of the ρ and B mesons in states of the two possible quantum numbers J^P =1⁺ and 2^–. The procedure consists of a zero-width approximation to the transition amplitudes in states of given J and L, crossing-symmetric relations, and the one-dimensional dispersion representations of the invariant amplitudes. The relationship between the invariant amplitudes and the helicity amplitudes greatly facilitates this procedure. The t-channel reaction is also analyzed. A method of solution of the partial-wave dispersion relations is discussed based on a recently developed formalism, and is extended further to avoid the difficulty associated with the zeros of the driving forces. A systematic program to understand the quantum numbers of the B meson as a πω resonance is also discussed. The qualitative nature of the forces due to the B exchange in states of each possible quantum number is briefly sketched. Finally, a model calculation which favors a 2^– state of the B meson is presented.« less

In June, 1947, at the Shelter Island Conference on Theoretical Physics, the contradiction between the large production cross section for mesons in the high atmosphere and their subsequent extremely weak nuclear interaction at low altitudes were subjected to a careful arid searching scrutiny. Conversi, Pancini, and Piccioni had already performed their classic experiment on the absorption of slow negative mesons in matter of low atomic number and Fermi, Teller, and Weisskopf had shown that the observed decay of the negative mesons implied a meson interaction with nuclei weaker by a factor of 10 or more than that previously assumed. Manymore » suggestions were offered to explain the apparent lack of reversibility between emission and absorption of mesons and the two-meson hypothesis put forward by the author as a way out of the difficulties seemed but another "shot in the dark". However, before the Shelter Island meeting was many weeks old, the first two-meson photographs obtained by Powell and his collaborators reached the U. S. and provided the initial evidence in favor of the two-meson theory. Since then many experiments have confirmed the idea that the heavier or π-mesons are strongly coupled to nucleons whereas the lighter or μ-mesons are the decay products of π-mesons and experience weak interactions with nucleons. Further, we shall not enter into a discussion of these experiments here but it is useful to point out that all these experiments imply that π-mesons should react vigorously with the nuclei of hydrogen and deuterium whereas μ-meson reactions with these two lightest nuclei should be quite unobservable. Hence, when we speak of meson reactions in hydrogen and deuterium, we mean π-meson reactions.« less