At the Weizmann Institute of Science, an experiment was carried out that has direct implications for a factor that is at the seam between the two worlds: neutrino physics and solar physics
Two of the three winners of the Nobel Prize in Physics this year, Raymond Davis and Masatoshi Koshiba, won the prize for fundamental discoveries along a long path that led to impressive discoveries last year: experiments carried out at the SNO (Solar Neutrino Observatory) laboratory in Canada proved that the neutrino particles, which are classified into three types, can pass from one type On the other hand, and as a consequence of this, it was proved that the neutrino has a (very small) mass. These experiments and the conclusions drawn from them are the highlight of a large-scale work carried out in recent years in two fields of physics: the study of neutrinos and the study of the sun and the processes that take place in it. However, in order to achieve a better understanding of the observed processes and phenomena, additional experiments are being carried out in this field in different parts of the world.
In this framework, an experiment was carried out at the Weizmann Institute of Science that has direct implications for a factor that is at the seam between the two worlds: neutrino physics and solar physics. This factor is the flux of boron 8 nuclei, which the measurements carried out at the institute will allow to determine with greater precision than was previously possible. The creation and decay of boron 8 are links in the chain of fusion processes that occur in the sun, but the importance of boron 8 stems, among other things, from the fact that during beta decay it produces high-energy neutrinos (these are the particles studied in the experiments carried out at SNO and in the Davis experiments).
Prof. Michael Hess and Prof. Gvirol Goldring from the Department of Particle Physics at the Weizmann Institute of Science, and the postdoctoral researchers Dr. Lagi Bayi and Dr. Kristina Bordano, recently recreated a process that also occurs in the center of the Sun: the fusion of a proton and a beryllium 7 nucleus, which ends in the creation of Boron 8 nucleus. This nucleus (boron 8) decays in about a second, emitting a positron and a neutrino - and turns into beryllium 8. This nucleus immediately turns into two alpha particles (helium nuclei), which are the particles observed in the experiment. These alpha particles are a tiny part of the accumulated helium reservoir in the sun, but the importance of the process reproduced in the experiment is not related to the helium it produces and not to the production of energy, but to the fact that it serves as a source of neutrinos which were a central means in the study of nuclear fusion processes in the sun, and more recently also in the study of the physics of the neutrinos themselves.
The experiment was carried out in the Van de Graaff accelerator, which has been operating at this institute for more than forty years. Beryllium 7, which is a radioactive isotope with a lifetime of about two months, was produced in the radioactive ion accelerator ISOLDE at the European particle laboratory CERN. Thus, in one study, one of the most advanced particle accelerator systems in the world was combined with the old and faithful accelerator, the forty-year-old van de Graaf at the Weizmann Institute of Science.
The description of this research is published these days in the journal: Physical Review Letters.
Scientists from the Sorek Nuclear Research Center, the ISOLDE radioactive ion accelerator at the European Particle Laboratory, CERN, and the Shecher Institute also participated in the study.
