High-precision atomic mass measurements for a CKM unitarity test

摘要

The Cabibbo-Kobayashi-Maskawa (CKM) quark-mixing matrix describes the transformation of quarks from weak-force eigenstates to mass eigenstates. The most contributing element in this matrix is the up-down matrix element Vud, derived in most precise way from the nuclear beta decays and in particular, from decays having superallowed 0~+ → 0~+ decay branch. What high-precision mass spectrometry community can offer are decay energies of such decays derived from parent-daughter mass differences, which are ideally, and in almost all cases, determined with Penning trap mass spectrometry directly from parent-daughter cyclotron frequency ratio. Typically frequency (and thus mass) ratios are determined with 10~(-9) relative precision, which allows decay energies to be determined within 100eV-level.