Borexino Collaboration Receives Giuseppe and Vanna Cocconi Prize


The European Physical Society has decided to present the Borexino Collaboration with the 2021 Giuseppe and Vanna Cocconi Prize. The Collaboration receives the prize for its ground-breaking observation of solar neutrinos, which provided unique and comprehensive insights into the Sun as a nuclear fusion engine.


Scientists at the Borexino Collaboration have been conducting research on solar neutrinos for 14 years. With the observatory for the nearly unobservable "ghost particles" located 1400 meters below the Earth's surface in the Gran Sasso Massif near Rome, the researchers have found missing puzzle pieces in the mechanism of solar nuclear fusion several times.

The researchers are presented with the Giuseppe and Vanna Cocconi Prize for their extraordinary findings on two different processes powering our star: In 2018, they published the most comprehensive analysis to date of neutrinos from the nuclear fusion processes inside the Sun, in particular more accurate and significant data from the various steps of the so-called "pp process." A few months ago, researchers succeeded in demonstrating for the first time the existence of the so-called CNO fusion cycle in nature: They discovered solar neutrinos originating from this process.

Interview with Professor Livia Ludhova

Professor Livia Ludhova is head of the neutrino group at the Jülich Institute for Nuclear Physics (IKP-2).

Prof. Ludhova, what are solar neutrinos and why are they so important for our understanding of how the Sun works?

Solar neutrinos are emitted during the nuclear reactions that lead to the fusion of hydrogen into helium inside the Sun. This complex process produces neutrinos with characteristic energy distributions through multiple interactions. The proportions of the rates of these interactions depend on various properties of the Sun, such as its temperature profile or chemical composition. Thus, the number and energy of detected solar neutrinos give us valuable information about the interior of our star and thus about the processes that make life on Earth possible.

What is the Borexino Collaboration?

The Borexino Collaboration is an international team of about 100 scientists from Italy, Germany, USA, Russia, Poland, and France. When the Collaboration was founded, the primary goal was to measure so-called beryllium-7 neutrinos from a particular interaction of the proton-proton (pp) reaction chain. However, it quickly became apparent that the Borexino detector achieved even better performance than we had originally planned. Therefore, we did not have to limit ourselves to Be-7 neutrinos – we managed to measure all types of solar neutrinos.

The Borexino observatory is located in the largest underground laboratory in the world, the Laboratori Nazionali del Gran Sasso in Italy. At the heart of the Borexino detector is an extremely thin-walled, spherical nylon balloon containing 280 tonnes of a special scintillator fluid. Tiny light flashes occur in it when the rare reactions with neutrinos happen. Individual light particles, photons, are detected by around 2000 sensors converting light into electrical impulses.

In addition to solar neutrinos, Borexino also measures geoneutrinos: Neutrinos from the decays of uranium-238 and thorium-232 inside the Earth. In addition, the Borexino collaboration has been able to more precisely constrain the predictions for several exotic processes: thus we are also searching for physics beyond the Standard Model of particle physics.

I myself am coordinating the overall analysis of Borexino and leading a neutrino group at the Jülich Institute for Nuclear Physics that is involved in many aspects of the experiment. Currently, the group consists of two postdocs, Giulio Settanta and Oemer Penek, four PhD students, Sindhujha Kumaran, Apeksha Singhal, Alexandre Goettel, and Luca Pelicci, and one master's student, Antonia Weßel. They are all heavily involved in the analysis of the Borexino data and have made many valuable contributions, as have Zara Bagdasarian and Mariia Redchuk in the past, who have since left our group and the collaboration.

Where do you go from here with your research now? What are your next goals?

The Borexino detector will stop taking data in 2021. The collaboration wants to try to improve the precision of the measurement of solar CNO neutrinos, since the thermal stability of detector, an important feature for the CNO measurement, is steadily improving.

We also plan to use the Borexino detector to observe the direction of solar neutrinos for the first time in a liquid scintillator detector. If we succeed to reconstruct the direction of the neutrino signal in the analysis, all signals coming from other directions can be suppressed. This new analysis technique can be then exploited to improve sensitivity to neutrino signals, also in future liquid scintillator experiments, such as in JUNO, the Jiangmen Underground Neutrino Observatory, in which the Jülich group is also involved.

Professor Livia Ludhova

Professor Livia Ludhova is head of the neutrino group at the Jülich Institute of Nuclear Physics (IKP-2) and Professor at the Physics Institute IIIB, RWTH Aachen University. Her group is financed by the Recruitment Initiative of the Helmholtz Association, a recognition awarded in November 2015. She is specialized in low-energy neutrino physics with large-volume liquid-scintillator detectors, in particular in solar neutrinos, geoneutrinos, and neutrino mass ordering. She is a member of the Borexino and JUNO collaborations and physics co-coordinator of Borexino. In the past, she has worked in the field of exotic atoms (muonic and kaonic hydrogen) and metamorphic petrology (Variscan evolution in Tatra Mountains, Western Carpathians).