New Platform can Help Study the Principle of Parity Violation in Atomic Nuclei

The aim of the successful hypothesis made by Dionysis Antypas is to develop an innovative platform to perform fundamental tests in particle and nuclear physics based on the detection of isotopic difference of parity violation in atomic nuclei.

Dr Dionysis Antypas. Image Credit: © Nataniel Figueroa.

The European Research Council (ERC) will fund the latest project called “YbFUN”—in which Yb denotes ytterbium, a rare earth metal—with an ERC Starting Grant valued at EUR 1.46 million. The YbFUN project will be conducted at the Johannes Gutenberg University Mainz (JGU) for the next five years.

Physics has long believed that the laws of nature in this world as well as in the mirror world would be identical, and that parity would be maintained. Later in the late 1950s, scientists found that this principle was violated in the world of elementary particles, or more accurately, in the world of the weak interaction.

Since then, parity violation has been a matter of scientific research. Physicists from the PRISMA+ Cluster of Excellence at JGU and from the Helmholtz Institute Mainz (HIM) specifically targeted the parity violation of ytterbium atoms that have different numbers of neutrons in the nucleus—that is, different isotopes of this element.

The team achieved excellent success in 2018.

We selected a chain of four of ytterbium’s seven isotopes and confirmed the predictions of the Standard Model: the more neutrons in the nucleus, the greater the parity violation effect.

Dr Dionysis Antypas, PhD, Physicist, Purdue University

Using an apparatus at HIM, the physicists performed the study by stimulating the ytterbium atoms by laser light and quantifying the amplitude of the parity violation in the presence of both magnetic and electric fields.

New Method Provides a Window into the Effects of Weak Interaction in Atoms

Published in the leading Nature Physics journal, the promising outcomes inspired Antypas to track the project as explained in the actual proposal.

We will significantly expand the existing approaches to study isotope-dependent APV variation. This way we want to establish the method as a powerful tool at the interdisciplinary junction between atomic, nuclear, and particle physics in order to make measurements of the atomic effects of the weak interaction with unprecedented accuracy. Such a platform would be complementary to high-energy physics experiments in large facilities.

Dr Dionysis Antypas, PhD, Physicist, Purdue University

More explicitly, comparing the Atomic Parity Violation (APV) effect in varied isotopes of the same atomic species is rather a sensitive method to analyze the spread of neutrons in the nucleus, which, consequently, is closely associated with the size and structure of neutron stars.

Undoubtedly, the same physics models have described neutron-dense nuclear matter that appears in largely different sizes, like a neutron star (of size ≈10 km) and the Yb nucleus (of size ≈1 fm, or 10–15 m).

As part of their previous measurements, the team has also shared data on an additional Z boson. Z bosons normally control the feeble interaction, and investigators in the field speculated the presence of an additional Z boson, called the “Z” or “Z prime” with a relatively smaller mass when compared to that of the established Z boson.

As a result, the latest platform to be established in the context of the YbFUN project is also a probe of supplementary vector bosons, beyond the Standard Model of particle physics.

Eventually, the analysis of nuclear-spin-dependent contributions to the APV effect detected in isotopes with nuclear spin is a sensitive method to study the intranuclear weak interactions, which are poorly understood even today.


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