3:30–4:30 pm Maria Goeppert-Mayer Lecture Hall
The Borexino Experiment: A parable of pioneering design, determined resolve, and textbook results
Andrea Pocar, UMass
Borexino is a large solar neutrino detector that has operated at the Laboratori Nazionali del Gran Sasso between May 2007 and October 2021. Neutrinos are detected via their elastic interaction with the electrons of a 300-ton liquid scintillator target, purified to achieve unprecedented levels of radio-purity. Borexino has measured the composition of the solar neutrino spectrum with unprecedented detail and precision, including all the components of the solar pp chain of nuclear reactions that fuse four protons into helium nuclei, neutrinos, and heat. In 2020, Borexino made the first measurement of solar CNO neutrinos, produced along a catalytic hydrogen fusion cycle enabled by the presence in the solar plasma of heavier elements, or “metals”. This observation, refined in 2022, caps three decades since the conception of Borexino and provides remarkable experimental confirmation for the pioneering solar modeling by Hans Bethe et al. dating back to the 1930s. Using solar neutrinos, Borexino has also recently demonstrated that directional information can be extracted from MeV-scale electron recoils in liquid scintillator and measured the earth’s orbital parameters around the sun.
This talk will review the technical and scientific legacy of Borexino from its beginnings, present the latest measurements, and provide an outlook on its final science as well as a personal view on how the Borexino story feeds future science.