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HK: Fachverband Physik der Hadronen und Kerne

HK 10: Structure and Dynamics of Nuclei II

HK 10.2: Vortrag

Montag, 20. März 2023, 17:00–17:15, SCH/A215

The Charge Radius of ^26,26mAl and its implication for CKM unitarity — •Peter Plattner — Max-Planck-Institut fuer Kernphysik, Heidelberg, Germany

For the COLLAPS and IGISOL collaborations.

In the study of atomic nuclei, nuclear charge radii provide intriguing physics insights into the evolution of nuclear structure far away from stability. Furthermore, charge radii have been used as experimental input for the determination of Vud of the CKM quark mixing matrix from superallowed nuclear β-decays. In the Standard Model of particle physics, the CKM matrix is predicted to be unitary but recent reviews of the matrix values show a 2.2σ deviation for one of its unitarity tests.

This contribution will present the recent work of combined measurements of the charge radii of ^26,26mAl by means of Collinear Laser Spectroscopy (CLS) at the COLLAPS experiment/ISOLDE and at the IGISOL facility/Jyvaskyla, Finland. CLS takes advantage of the interaction between the atomic nucleus and its surrounding electrons giving rise to the hyperfine structure. Thus, properties of nuclear ground states and long-lived isomers, including nuclear charge radii, can be inferred from measured hyperfine spectra. Prior to the present work, the charge radius of the superallowed β emitter ^26mAl was not known experimentally but was extrapolated to evaluate the isospin symmetry breaking (ISB) correction required for the determination of Vud.

The present measurements reveal a charge radius of ^26mAl which differs by more than 4 standard deviations from the value assumed in previous ISB calculations.