Spontaneous Muon Emission during Fission, a New Nuclear Radioactivity

TL;DR

This paper presents a theoretical model predicting spontaneous muon emission during nuclear fission, highlighting the potential for such radioactivity in superheavy nuclei and reviewing related experimental efforts.

Contribution

It introduces a fission-like model for nuclear muonic radioactivity, accounting for muon-fissility and barrier heights, and applies it to superheavy elements and experimental data.

Findings

Most superheavy nuclei have muonic fissility parameter X=1, indicating no classical barrier for muon emission.

Numerical estimates of muonic radioactivity yields are provided for transuranium elements.

Experimental results from fission spectrometry and proposed underground searches are reviewed.

Abstract

In this paper the essential theoretical predictions for the nuclear muonic radioactivity are presented by using a special fission-like model similar with that used in description of the pionic emission during fission. Hence, a fission-like model for the muonic radioactivity takes into account the essential degree of freedom of the system: muon-fissility, muon-fission barrier height, etc. Using this model it was shown that most of the SHE-nuclei lie in the region where the muonic fissility parameters attain their limiting value X=1. Hence, the SHE-region is characterized by the absence of a classical barrier toward spontaneous muon and pion emissions. Numerical estimations on the yields for the natural muonic radioactivities of the transuranium elements as well numerical values for barrier heights are given only for even-even parent nuclei. Some experimental results from LCP-identification emission spectrum are reviewed. Also, the experimental results obtained by Khryachkov et al, using new spectrometer for investigation of ternary nuclear fission, are presented. The OPERA-experiment proposed to perform search for muonic radioactivity from lead nuclei, in the low background conditions offered by the Gran Sasso underground Laboratory (LNGS), is discussed.