The origins of the fragmentation of Fermi transitions for beta decay

par David Durel (CEA, DAM, DIF)

jeudi 12 févr. 2026, 14:00 → 15:00 Europe/Paris

100/2-A201 - Salle A201 (IJCLab)

A theoretical description of beta radioactivity involves different modes of transition between the states of the mother and daughter nuclei. For each of these modes, we obtain an energy spectrum in which we observe a whole range of transitions. Among these transition modes, there is one, the Fermi transition, which is said that it cannot fragment, meaning that there must be one and only one transition. However, theoretical calculations based on an HFB+pn-QRPA model show us a spectrum with several transitions...

 

I propose a presentation in which I will attempt to explain the origins of this fragmentation based on the structural elements provided by the HFB and pn-QRPA calculations. But first, I will dedicate a portion of this presentation to clearly defining the methods used (HFB, pn-QRPA, etc) as well as a very brief overview of the theory describing beta radioactivity. These concepts form the basis for understanding the shell filling mechanism and provide information for interpreting the shape of wave functions. Through a systematic study of the (even-even) nuclei of $ N=50 $ and $ Z=50 $ chains, we can understand the behavior of this fragmentation and thus its origin. The comparison of our results with those obtained using other theoretical methods will be discussed, as well as putting them into perspective with regard to existing experimental data.