Half-Life Measurement of 11C for Testing the Standard Model

Abstract

The precision determination of the \(\mathcal {F}t\) value in T = 1∕2 mixed mirror transitions provides a method of determining the Vud element of the Cabibbo–Kobayashi–Maskawa matrix and serves as an important test of its unitarity and of the electroweak sector of the Standard Model. 11C, as the lightest such β+ decay, is particularly sensitive to physics beyond the Standard Model. Thus, a new, high-precision half-life measurement was conducted using the TwinSol facility of the Nuclear Science Laboratory at the University of Notre Dame. The new half-life, t1∕2 = 1220.27(26) s, is consistent with the previous values but significantly more precise, and the new world-average value is \(t_{1/2}^{\text{world}}=1220.41(32)\), a fivefold improvement over the previous value. This makes the 11C \(\mathcal {F}t^{\text{mirror}}\) value the most precise of all superallowed mixed mirror values and provides a strong impetus to the measurement of the Fermi-to-Gamow-Teller mixing ratio for the decay of 11C and thus allow the determination of Vud