9.10.2020 How Can the Basic Properties of Neutrinos be Probed by Nuclear Physics? (Jokiniemi)

The present knowledge of particle physics is based on the Standard Model. However, it has been proven that the Standard Model’s perception of neutrinos is not accurate, which makes the search of new physics beyond the Standard Model most intriguing. Currently, the most practical way to access the mass-scale and character of neutrinos is measuring neutrinoless double-beta decay – a hypothetical beyond-standard-model process – of atomic nuclei. In her thesis on theoretical nuclear physics, Jokiniemi studied how neutrinoless double-beta decay can be probed by measured nuclear processes, especially charge-exchange reactions and muon capture.
Published
9.10.2020

Neutrinoless double-beta decay is a radioactive decay process in which two neutrons of the decaying nucleus transform simultaneously into protons, and two electrons are emitted. This is currently one of the most important research topics in nuclear and particle physics. However, the study of neutrinoless double-beta decay is extremely challenging. In the dissertation it was investigated how other nuclear processes could pave the way for a better understanding of double beta decay. In particular, two processes have been studied in this work: charge-exchange reactions and muon capture.

Experimental research on charge-exchange reactions has recently taken a major leap forward. These reactions are related to the transitions in double beta decay, hence they provide valuable information on the nuclear structure dependence of double-beta decay.

By comparing the measurement results with the theoretical predictions, Lotta Jokiniemi managed in her dissertation to refine the values of the nuclear matrix elements related to double-beta decay.

In muon capture, muon — an electron-like but 200 times heavier lepton — is captured in the nucleus, causing a reaction that leads to nuclear transitions up to high excitation states. These transitions are also linked to double-beta decay.

Recently, for the first time, a muon capture strength function, i.e., the probabilities of muon capture for all nuclear excitation states, was measured.

“Comparing the experimental distribution to my calculations, I found an excellent fit between the results. Inspired by the result, I extended my calculation to other nuclei of experimental interest, offering an opportunity to compare the measured distributions with the calculated ones and thus refine the values of the parameters related to double beta decay, ”says Jokiniemi.

The study has been published in the Ģֱ's dissertation series JYU Dissertations, number 288, Jyväskylä 2020. ISBN 978-951-39-8304-8 (PDF), URN: ISBN: 978-951-39-8304-8, ISSN 2489-9003.
The publication is available in the JYX publication archive at:

More information:
Lotta Jokiniemi, lotta.m.jokiniemi@jyu.fi

M.Sc. Lotta Jokiniemi defends her doctoral dissertation in Physics "Probing neutrinoless double-beta decay by charge-exchange reactions and muon capture" at the Ģֱ on Friday 9th of October 2020. Opponent is Emeritus Professor Theocharis Kosmas (University of Ioannina, Greece) and Custos is Professor Jouni Suhonen (Ģֱ). The doctoral dissertation is held in English.

The audience can follow the dissertation online.
Link to the Zoom Webinar (Zoom application or Google Chrome web browser recommended):