A New Determination of the (Z,A) Dependence of Coherent Muon-to-Electron Conversion

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Auteurs principaux: Borrel, Léo, Hitlin, David G., Middleton, Sophie
Format: Preprint
Publié: 2024
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author Borrel, Léo
Hitlin, David G.
Middleton, Sophie
author_facet Borrel, Léo
Hitlin, David G.
Middleton, Sophie
contents Should muon-to-electron conversion in the field of a nucleus be found in the current generation of experiments, the measurement of the atomic number dependence of the process will become an important experimental goal. We present a new treatment of the (Z,A) dependence of coherent muon-to-electron conversion in 236 isotopes. Our approach differs from previous treatments in several ways. Firstly, we include the effect of permanent quadrupole deformation on the charged lepton flavor violating matrix elements, using the method of Barrett moments. This method also enables the addition of muonic X-ray nuclear size and shape determinations of the charge distribution to the electron scattering results used previously. Secondly, we employ a Hartree-Bogoliubov model to calculate neutron-related matrix elements for even-even nuclei. This takes into account the quadrupole deformation of the neutron distributions and the fact that neutrons are, in general, in different shell model orbits than protons. The calculated conversion rates differ from previous calculations, particularly in the region of large permanent quadrupole deformation. Finally, we propose an alternative normalization of the muon-to-electron conversion rated, which related more closely to what a given experiment acturally measures, and better separate lepton physics from nuclear physics effects.
format Preprint
id arxiv_https___arxiv_org_abs_2401_15025
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle A New Determination of the (Z,A) Dependence of Coherent Muon-to-Electron Conversion
Borrel, Léo
Hitlin, David G.
Middleton, Sophie
High Energy Physics - Phenomenology
High Energy Physics - Experiment
Nuclear Theory
Should muon-to-electron conversion in the field of a nucleus be found in the current generation of experiments, the measurement of the atomic number dependence of the process will become an important experimental goal. We present a new treatment of the (Z,A) dependence of coherent muon-to-electron conversion in 236 isotopes. Our approach differs from previous treatments in several ways. Firstly, we include the effect of permanent quadrupole deformation on the charged lepton flavor violating matrix elements, using the method of Barrett moments. This method also enables the addition of muonic X-ray nuclear size and shape determinations of the charge distribution to the electron scattering results used previously. Secondly, we employ a Hartree-Bogoliubov model to calculate neutron-related matrix elements for even-even nuclei. This takes into account the quadrupole deformation of the neutron distributions and the fact that neutrons are, in general, in different shell model orbits than protons. The calculated conversion rates differ from previous calculations, particularly in the region of large permanent quadrupole deformation. Finally, we propose an alternative normalization of the muon-to-electron conversion rated, which related more closely to what a given experiment acturally measures, and better separate lepton physics from nuclear physics effects.
title A New Determination of the (Z,A) Dependence of Coherent Muon-to-Electron Conversion
topic High Energy Physics - Phenomenology
High Energy Physics - Experiment
Nuclear Theory
url https://arxiv.org/abs/2401.15025