Determination of the 8B neutrino spectrum Original Research Article

We have measured the total energy of the alpha particles emitted following the beta-decay of 8B. The alpha particle energy spectrum is used to infer the shape of the 8B neutrino spectrum, which is an important input in the interpretation of experiments which detect energetic neutrinos from the Sun. The alpha-spectrum was measured with a new technique which involved the implantation of a beam of 8B ions into the mid-plane of a 91 μm thick planar Si detector, allowing both of the decay alpha particles to be observed in the same detector. Calibration was performed by implanting a beam of 20Na ions, which provide alpha lines in the energy region of interest. The experimental results are compared with a previous precision measurement of the alpha spectrum, and are found to disagree.