Neutrino Physics: Solar - Borexino

Virginia Polytechnic Institute And State University, Blacksburg VA

Investigators

Abstract

Solar neutrino research has already discovered massive neutrinos and flavor mixing, and is moving into an era where precision measurements can tell us about the inner workings of the Sun. The carbon-nitrogen-oxygen (CNO) cycle is one of the fusion reactions by which stars convert hydrogen to helium, releasing electron-neutrinos. Should this next period allow the Borexino detector to measure the CNO neutrino flux sufficiently well to infer the metallicity (the abundance of elements other than hydrogen or helium) of the sun's interior, it could test the fundamental assumption of homogeneity in the sun and provide crucial information regarding opacities in the solar interior that are important for helioseismology. Such studies could thus have a great impact on our understanding of the sun, stellar astrophysics, the link between planetary and stellar formation, as well as basic neutrino physics. This award provides funding for the continuing role of Virginia Tech in the Borexino experiment, the world's purest large-volume liquid scintillator detector located at the Gran Sasso National Laboratory in Italy, designed to measure the principle components of the neutrino spectrum coming from the Sun as it converts hydrogen into helium through fusion. They have measured the 7-Be, 8-B, and pep neutrino fluxes from the Sun, and set a limit on the CNO neutrino flux. The next three-year period with ultra-low background requires re-calibration to verify these results, and to prepare the collaboration to move into a new 'CNO focused' phase. The principle physics goals are 1) measurement of the CNO neutrino flux, 2) more precise results for the 7-Be and pep neutrino flux, and 3) a better result for the pp neutrino flux. The broader impact on science, technology and outreach that is expected from the program includes: the training of graduate and undergraduate students in current topical physics research; experience with deployment and utilization of ultra-clean calibration techniques; presentations of this research program to undergraduates, through research projects, student presentations, lectures, and problems - exposing the next generation of scientists from multiple fields to the excitement of astroparticle physics; and a broad engagement of the neutrino community through their Center for Neutrino Physics.