Order Feynman Diagrams Research Articles

Asymptotic estimates of Feynman diagrams

We derive asymptotic estimates for the most likely value of generical very high order Feynman diagram.

Dual Amplitude and Quark Dynamics

We regard the usual quark diagram as the lowest order Feynman diagram describing hadron dynamics. In the lowest order amplitude a factor V is introduced to obtain a dual one. Then the quark mass and the upper bound of the meson trajectory intercept can be predicted. Further the physical meaning of V is studied. Firstly, the role of V in the amplitude is analytically investigated. Secondly, we seek a possibility that V may effectively represent an interacting between quarks. Assuming some Feynman diagrams which may represent a part of the role of V, a Regge trajectory is derived by the perturbative calculation. The trajectory is expanded about t=0 and it is compared with the trajectory of our dual amplitude. Then the intercept of the leading ordinary-trajectory satisfies α(0)=1/2.

The meson exchange current effect in radiative np capture

The pion exchange current contribution to the thermal neutron proton radiative capture cross section is calculated on the basis of potential theory by extracting a local “absorptive exchange potential” from the corresponding fourth order Feynman diagram with the deuteron nucleon vertex on the mass shell. Taking into account that the repulsive core of nucleon interaction leads to modifications not only of the wave functions (which include off-mass shell properties of the deuteron nucleon vertex) but also of this absorptive OPE potential a result is obtained which explains the main part (⋍ 2 3 ) of the well-known 10%-discrepancy between experiment and impulse approximation.

A parton approach to dual models

The problem of correspondence of very high order unrenormalized Feynman diagrams to the dual model is discussed. The very high order Feynman diagrams are investigated using a statistical formalism recently developed.

Polarization of the Recoil Proton for Proton Compton Scattering Below the Pion Production Threshold

Abstract The polarization of the recoil proton for Compton scattering on protons below the pion production threshold, which arises from fourth order Feynman diagrams, is calculated by using the second order Compton amplitude in the unitarity condition. It is assumed that the second order amplitude can be approximated by the one proton intermediate state contribution. The polarization does not exceed 0.1% in the entire range of the scattering angle.

Dual Resonance Amplitude Corresponding to Globular Feynman Diagrams

Following the conjecture on the correspondence between the dual resonance amplitude and the very high order Feynman diagram, we calculate the dual resonance amplitude cor­ responding to the globular Feynman diagram. We find that it develops essential singularities in the Lorentz-invariant variables. It has been suggested by several authors 1 l' 2 l that amplitudes in the dual res­ onance model can be obtained by taking the continuum limit of the F eynman amplitudes corresponding to the very high order planar diagrams. It seems rather peculiar that only the planar Feynman diagram can lead to the dual reso­ nance amplitude. In general any Feynman diagram can be drawn in a three­ dimensional topological space. However, we need higher dimensional topolo­ gical spaces in order to discuss the continuum limits of the very high order Feynman diagrams. For example, the Klein-bottle-like Feynman diagram can be drawn in the three-dimensional space before taking the continuum limit. But, once we take the continuum limit, we need the four-dimensional space to draw

The process of Σ - Λ conversion following the nuclear absorption of [formula omitted] with the production of A π −

The second order process of the Σ-Λ conversion following the nuclear absorption of a kaon from a K meso-atomic orbit with the production of a negative pion is discussed, and calculated from a second order Feynman diagram. The momentum distributions of the recoiling nucleus and of the pion are computed for the K absorption in 4He and in deuterium. A semi-quantitative agreement with the data is obtained in all the cases. No attempt is made to calculate the absolute values of the reaction rates in question. The need of more and better data is stressed. The available data tend to favour the assumption of the 2P capture over that of the 1S capture in the case of 4He, but it is insufficient to rule out any one of the two cases.