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Abstract

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 V_ud, 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 100 eV-level. 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 V_ud, 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 100 eV-level.