The Physics & Astronomy Colloquium Series presents Live-Palm Kubushishi of Ohio University, discussing "Shaping the Halo: Deformation Effects in Weakly Bound Nuclei" on April 10.

Abstract
Halo nuclei are among the most exotic systems in nuclear physics. They exist
far from stability, close to the limits where nuclei can no longer bind additional
neutrons. Unlike ordinary nuclei, halo nuclei have an unusually large spatial
extension. This striking property arises from their peculiar structure: a compact
nuclear core surrounded by one or two very weakly bound neutrons. Because
these neutrons are so loosely bound, quantum mechanics allows them to extend
far from the core, forming a diffuse “halo”.
Since halo nuclei are extremely short-lived, they cannot be studied in the
same way as stable nuclei. Instead, we probe them indirectly through nuclear reactions.
Interpreting these experiments requires theoretical models that capture
the essential physics of these fragile systems without becoming unnecessarily
complicated. A powerful framework developed for this purpose is halo effective
field theory (halo-EFT), which provides a systematic low-energy description of
halo nuclei. However, in its standard form this approach cannot fully account
for situations where the nuclear core itself becomes excited or deformed.
In the first part of this talk, I will present a practical extension of halo-
EFT that allows the nuclear core to be deformed. This enables the description
of deformed one-neutron halo nuclei in a unified and relatively simple way. I
will show how deformation affects observable properties such as energy levels
and reaction probabilities. As a key example, I will discuss the well-known
halo nucleus 11Be, for which extensive experimental data and state-of-the-art
theoretical calculations exist. These results illustrate how the interplay between
the halo neutron and a deformable core shapes the structure of the nucleus.
In the second part of the talk, I will outline the foundations of a new effective
field theory designed for light deformed halo nuclei. The goal is to build a description
that remains simple, yet can be systematically improved and provides
controlled theoretical uncertainties.
Overall, this work aims to provide a clearer and more unified picture of how
loosely bound quantum systems behave at the edge of nuclear stability, and to
improve the connection between experimental observations and the underlying
nuclear dynamics