Quark picture put to the test

2023/11/27

Fig.: If the CKM matrix is not unitary, there could be a fourth family of quarks. Source of the figure: APS/Ryan Wilkinson (Physics Viewpoint: https://physics.aps.org/articles/v16/199)

The measurement of the isomer shift and difference of charge radii between Al-26 and the isomer Al-26m has been published in Physical Review Letters with an Editor's suggestion and is featured in “Physics Viewpoint”.
The new value of the isomer is significantly higher than previously reported and this affects the unitarity of the Cabibbo-Kobayashi-Maskawa (CKM) matrix since the beta decay rate of this isomer is one of the most precisely measured ones and constrains the V_ud value. More information can be found in the paper, which is freely available.