Branching ratio for the superallowed beta-decay of 10C

Superallowed β decays play a key role in testing the Standard Model of Particle Physics. These decays occur between nuclear analog states having spin-parity of 0⁺ and isospin T = 1 . Currently, and in the foreseeable future, they offer the most accurate value for the V_ud matrix element of the Cabibbo-Kobayashi-Maskawa quark mixing matrix. Each superallowed transition is characterized with an Ft value combining both experimental and theoretical quantities. We have just made a preliminary new measurement of the ¹⁰C branching ratio, which currently is the least precisely known quantity for any of the ``traditional nine'' superallowed transitions. Furthermore, ¹⁰C is the only case that appears to have its corrected Ft value outside the world average value, which could be explained with the existence of a scalar current. We performed the branching-ratio measurement with a β- γ coincidence setup using a scintillator for β and an HPGe with +/-0.15% calibrated relative efficiency for γ detection. Since the branching ratio is obtained from the ratio of intensities of 718 keV and 1022 keV γ lines, most systematic uncertainties cancel out. I will show an overview of the experiment and preliminary results.