Orateur
Description
The Cabibbo-Kobayashi-Maskawa (CKM) matrix describes the weak charged-current interactions of quarks within the framework of the Standard Model of particle physics. It governs, in particular, $\beta$ decays through coupling with the $W^{\pm}$ bosons. To test its validity, the terms of the CKM matrix must be determined with high precision, and their uncertainties must be well understood. One of the tests of its structure relies on the unitarity relation $( \lvert V_{ud} \rvert ^2 + \lvert V_{us} \rvert ^2 + \lvert V_{ub} \rvert ^2 = 1) $. Any deviation from this unitarity could indicate the emergence of new physics beyond the Standard Model.
The dominant element of the CKM matrix, $V_{ud}$, can be experimentally determined, particularly through superallowed β transitions (lifetime and branching ratio). For $0^+ \rightarrow 0^+$ transitions, the corrected value $\cal F$t (including radiative corrections and isospin symmetry-breaking corrections) allows the extraction of the $V_{ud}$ term. Among the nuclei studied, the decay of 10C stands out due to one of the largest uncertainties in the branching ratio.
Furthermore, these transitions provide a unique probe to test the Standard Model, which predicts a purely V-A (vector and axial) weak interaction. However, in the context of physics beyond the Standard Model, extensions such as leptoquarks or charged Higgs bosons could introduce exotic contributions, such as a scalar component in the weak interaction. Thus, the parameter $C_S$ can be constrained. This contribution introduces a Fierz interference term, $b_F$, for Fermi transitions, which modifies the shape of the $\beta$ spectrum and the branching ratio.
The experiment was performed at LNL using the AGATA $\gamma$-ray tracking array. The $^{10}C$ nucleus was produced via the (p,n) reaction induced by a proton beam at 10 MeV impinging on a $^{10}B$ target. In addition, the superallowed $\beta$ branch populates the excited 0+ state of $^{10}B$ at 1740 keV, which de-excites by emitting a 1021.7 keV $\gamma$ ray. This energy coincides with the pileup of two annihilation photons (2 × 511 keV) produced in the $\beta ^+$ decay, thus introducing a contamination of the peak. A highly segmented tracking detector allows this effect to be better identified and corrected.
The experimental setup and the preliminary results will be presented and discussed.