Gianpaolo Bellini

Gianpaolo Bellini was born in Milan, Italy, on 12 June 1935. He trained as a physicist in Milan and held a NATO fellowship at the Ecole Normale Superieure in Orsay, France, in 1966 and 1967. He obtained the Italian libera docenza, the national qualification to teach at university level, in 1967.

Bellini spent his academic career at the University of Milan, first as an assistant professor from 1969 to 1976 and then as a full professor from 1976. He was a CERN fellow in 1984 and 1985 and directed the university's doctoral school in physics, astrophysics and applied physics from 2003 to 2008.

From the late 1960s through the 1990s he led joint University of Milan and INFN groups at CERN, at the Institute for High Energy Physics in Protvino, Russia, and at Fermilab in the United States. He helped establish coherent production on nuclei as a way to study how hadrons are produced, introducing the idea of an active target made of thin silicon layers. His group built one of the first silicon micro-strip vertex detectors in a large spectrometer, for the Fermilab E687 experiment, which allowed precise measurements of the lifetimes of charmed mesons and baryons.

In 1990 he proposed Borexino, an ultra-pure liquid scintillator detector deep under the Gran Sasso mountain in central Italy, designed with Frank Calaprice and Raju Raghavan to detect low-energy solar neutrinos. The collaboration developed purification techniques that set new standards for low radioactivity. Bellini was its spokesperson from 1990 to 2012 and remained on its institutional board afterwards. Borexino measured the pp, beryllium-7, pep and boron-8 solar neutrinos, tested how neutrinos change flavour on their way out of the Sun, made the first observation of geoneutrinos and in 2020 published the first direct evidence of neutrinos from the CNO fusion cycle.

Within INFN he sat on the board of directors from 1973 to 1983, served as vice president from 1983 to 1989 and chaired the national computing committee from 1981 to 1983. He coordinated the national programme on applied superconductivity for LEP2 and the LHC from 1993 to 1999. In Europe he served on the council of the European Physical Society and on the European Committee for Future Accelerators. He founded the Physics in Collision conference series, co-founded the Heavy Quarks and Leptons conferences, edited for the journal EPJ Plus, and founded and for 15 years directed ISAPP, the International School of Astroparticle Physics network.

Bellini lived in Foresto Sparso, in the province of Bergamo, in his later years. Colleagues remembered him as a determined and demanding leader who also took a warm personal interest in the people who worked with him, many of whom described the Borexino collaboration as a family. He kept working on the experiment until the end of his life, and in 2025 longtime collaborators marked his 90th birthday with an event honouring his contributions to science.

Gianpaolo Bellini died at his home in Foresto Sparso, near Bergamo, on 12 August 2026, at the age of 91. INFN announced his death on 13 August. No cause of death was made public. Colleagues noted that he died on the day of a solar eclipse, after a lifetime spent studying the Sun.

INFN president Antonio Zoccoli said: "Today we lose a great scientist, who made a fundamental contribution to the study of solar neutrinos and to understanding the reactions that power the Sun and the stars." Borexino co-spokesperson Marco Pallavicini called his death a great loss, both personal and scientific, and Ezio Previtali, director of the Gran Sasso laboratories, said his scientific legacy would be a reference point for future generations of physicists. Messages of condolence to his family came from Borexino colleagues in Italy, Germany, Russia, Poland, Portugal and the United States.

Bellini is credited with turning solar neutrino physics into a precision science and with helping make the Gran Sasso National Laboratory one of the world's leading centres for astroparticle physics. Borexino's measurements of the Sun's fusion reactions and of neutrinos from inside the Earth remain landmark results, and the Italian postal service issued a stamp honouring the experiment in 2014.

His honours included the Bruno Pontecorvo Prize of the Joint Institute for Nuclear Research in Dubna (2016), the Enrico Fermi Prize of the Italian Physical Society (2017) and, with the Borexino collaboration, the Giuseppe and Vanna Cocconi Prize of the European Physical Society (2021). He was a member of the Istituto Lombardo Academy of Sciences and Letters and an honorary member of the Italian Physical Society.