Conveners
February 18 Morning Session: Antimatter
- Timothy Friesen (University of Calgary)
February 18 Morning Session: Nuclear Structure
- Marcella Berg (University of Regina)
The symmetry between matter and antimatter is one of the great unresolved questions in fundamental physics, as it underscores the discrepancies between the Standard Model and cosmological observations. Many experiments have been performed to compare the properties of antimatter to matter at great precision. However, gravitation has so far eluded these efforts due to the difficulty measuring...
ALPHA-g has completed a successful run in 2022 in the pursuit of measuring the gravitational mass of antihydrogen. This apparatus was designed to test whether antimatter follows Einstein’s Weak Equivalence Principle (WEP), where the acceleration due to gravity that a body experiences is independent of its structure or composition. A measurement of the gravitational mass of antimatter has never...
Antimatter lies at the heart of many of the universe’s unanswered questions, but direct study of antimatter structures is technically difficult. ALPHA-g promises the first direct free-fall observation of the Earth’s gravitational force acting on anti-atoms, by precisely recording the annihilation positions of anti-hydrogen atoms after a controlled release from a magnetic trap. Reconstructing...
The Antihydrogen Laser Physics Apparatus (ALPHA) collaboration uses low energy antiprotons to produce, trap, and study the bound state of an antiproton and positron, antihydrogen. Hydrogen has been studied extensively through history and has many physical properties known to a high precision experimentally and theoretically. Therefore, comparisons between hydrogen and its antimatter equivalent...
It has been known for many years that an electron and its antiparticle, the positron, may together form a metastable hydrogen-like atom, known as positronium or Ps. In 1946, Wheeler speculated that two Ps atoms may combine to form the positronium molecule (Ps$_2$) stable with respect to auto-dissociation. In 2007, the existence of Ps$_2$ was confirmed experimentally by David Cassidy and? Allen...
Nuclei away from the line of stability have been found to demonstrate behavior that is inconsistent with the traditional magic numbers of the spherical shell model. This has led to the concept of the evolution of nuclear shell structure in exotic nuclei, and the neutron-rich calcium isotopes are a key testing ground of these theories; there have been conflicting results from various...
The term ‘island of inversion’ is used to refer to a region of the nuclear landscape in which deformed intruder configurations dominate nuclear ground states over the spherical configurations naively expected from the shell model. Theoretical models of the inversion mechanism can be tested through detailed studies of the nuclear structure of transitional nuclei, in which the normal and...
Clustering in nuclei provides an alternative description to their nuclear structure in addition to the Nuclear Shell Model. Although alpha ($^4$He nucleus) clusters are widely accepted to be essential to the understanding of the structure of light nuclei, such as the Hoyle state in $^{12}$C, it was experimentally observed in heavy nuclei only recently in $^{212}$Po. The observation showed that...
Nuclear theories often operate under the assumption that the strong nuclear force is charge independent. As a result, it is expected that mirror nuclei, which are identical under the exchange of total number of protons and neutrons, will have similar nuclear structures when Coulombic contributions are considered. Under the assumption of charge dependence, protons and neutrons are grouped...
Neutron rich Mg isotopes far from stability belong to a region known as the island of inversion where the single particle description of the shell model breaks down, and the predicted configuration of the nuclear states becomes inverted. Nuclei in this region also exhibit collective behaviour in which multiple particle interactions play a significant role in nuclear matrix elements. These...
The nucleus, made up of protons and neutrons, exhibits a shell-like structure consisting of orbitals described by quantum mechanics. This has been demonstrated by extensive experimental observables, which reveal that nuclei possessing specific "magic numbers" of neutrons or protons exhibit particular characteristics well described in the nuclear shell model. The tin isotopes, with a closed...
