Physics Colloquium

**Isospin-symmetry and its breaking: from exotic nuclei to fundamental interactions and nuclear astrophysics**

Dr. Nadezda Smirnova

Associate Professor

Centre d'Etudes Nucleaires de Bordeaux-Gradignan (CENBG)

University of Bordeaux

Atomic nuclei are specific quantum many-body systems composed of two species of fermions -- protons and neutrons. A similarity between a proton and a neutron with respect to strong interactions allowed to introduce an approximate, but very useful symmetry called* isospin symmetry*. It has always been advantageous for formulation of nuclear structure models, as well as for construction of the *N N* potential. However, isospin symmetry is broken due to the *u* and *d* quarks mass difference and electromagnetic interactions between the quarks. This small breaking of isospin symmetry represents an important issue in nuclear physics and it must be well controlled theoretically for a large class of problems relevant to the structure of exotic nuclei, fundamental interaction studies and nuclear astrophysics. Numerous experimental programs at present and future rare isotope beam facilities are searching nowadays for a tiny degree of isospin-symmetry breaking in studies of exotic proton-rich nuclei and nuclei along *N = Z* line.

The talk will review the fundamental concepts of isospin symmetry and explain motivations for theoretical developments dedicated to the accurate description of isospin-symmetry breaking. Then, after introducing a state-of-the-art shell-model framework, we will discuss in more detail two applications. First, we will present a new method of extraction of isospin impurities from β-delayed proton-gamma emission. Second, we will show our advances in theoretical calculations of isospin-symmetry breaking corrections to 0 ^{+} → 0 ^{+} superallowed nuclear β-decay, which is known to provide important testing grounds for the fundamental symmetries underlying the Standard Model of particle physics.

*Hosted by Prof. Surman*

*All interested persons are invited to attend remotely—email physics@nd.edu for information.*