Study of weak magnetism by precision spectrum shape measurements in nuclear beta decay

Nuclear beta decays play an important role in uncovering the nature of the weak interaction. The weak magnetism (WM) form factor, bWM, is generally a small correction to the beta decay rate that arises at first order as an interference term between the dominant Gamow-Teller and the magnetic dipole contributions to the weak current. This form factor is still poorly known for nuclei with higher atomic number. We performed a careful analysis of the measured beta spectrum shape for Gamow-Teller transitions in In-114 and P-32 nuclei. The precision spectrum shape measurements were carried out using the miniBETA spectrometer consisting of a low-mass, low-Z multi-wire gas tracker and a plastic scintillator energy detector. The preliminary results for the weak magnetism extraction for In-114 and P-32 nuclei are presented.