A remark on the Primakoff effect

TL;DR

This paper discusses the Primakoff effect in nuclear reactions, emphasizing the importance of Coulomb-form factors in accurately extracting electromagnetic decay rates from experimental data.

Contribution

It highlights the impact of Coulomb-form factors on the Primakoff effect and provides insights into their influence on decay rate measurements.

Findings

Coulomb-form factors can reduce cross-section values by up to 40%.

Proper treatment of Coulomb-form factors is crucial for accurate decay rate determination.

The peak cross-section is sensitive to the ratio of transverse and longitudinal momentum transfers.

Abstract

The coherent-nuclear reaction a + A -> a* + A is in the small-angle region dominated by the one-photon-exchange mechanism, often referred to as the Primakoff effect. In this region information about the electromagnetic decay a* -> a + gamma can be obtained. Well-known examples are the two-photon decays of the pi- and eta-mesons. Also decays of charged hadrons can be studied. For charged hadrons the one-photon-exchange amplitude comes with a Coulomb-phase factor and a Coulomb-form factor, which depend on the ratio between transverse- and logitudinal-momentum transfers, the latter being fixed. At the peak of the cross-section distribution, where the two momentum transfers are equal, the form factor could cut down the cross-section value by as much as 40 %. Consequently, a determination of a radiative-decay rate that relies on the peak value becomes sensitive to a proper treatment of the Coulomb-form factor.