Milla Baldo Ceolin 1924–2011

At the end of November the particle-physics community lost one of its most inquisitive, enthusiastic and active members, when Milla Baldo Ceolin, emeritus professor at the University of Padua, passed away after several months of disabling illness.

After graduating in Padua in 1952, Milla began her scientific career in research with balloon-borne nuclear emulsions exposed to cosmic rays in the high atmosphere. She then took part in a systematic study of the K0K0 system produced by the new generation of accelerators in collaboration with W F Fry of the University of Wisconsin, also measuring the K1–K2 mass difference. In a subsequent exposure of nuclear emulsion to a pion beam from the Bevatron at Berkeley, in 1958 Milla and D J Prowse discovered the first antihyperon: the antilambda.

At the beginning of the 1960s she decided to change detection technique and began experiments with bubble chambers at Argonne, CERN and the Institute for Theoretical and Experimental Physics (ITEP) in Moscow to investigate selection rules and conservation laws in the kaon system, with higher statistics. In the meantime her group in Padua grew steadily, working in international collaborations.

The main field of her investigations changed to neutrino physics after the discovery of neutral currents in 1973. The NUE experiment at CERN, carried out with Helmut Faissner’s group at Aachen, used a set of large spark chambers to measure, for the first time, both neutrino and antineutrino elastic-scattering cross-sections off electrons and provided a value for the Weinberg angle, sin2θW They also obtained new results in other neutral-current reactions and coherent processes on aluminium nuclei. Returning to the bubble-chamber technique, but this time with liquid deuterium, in a large collaboration (Italy, France, the Netherlands and Norway) at CERN’s Super Proton Synchrotron, Milla and colleagues performed systematic investigations on neutrino neutral- and charged-currents on (quasi) free protons and neutrons.

In 1976 Milla proposed an experiment on νμ → νe oscillations with a long baseline and a low-energy neutrino beam at CERN. Carried out a few years later, it found no evidence for oscillations but set important limits on the oscillation parameters. Her curiosity for quantum mixings then turned to the search for neutron–antineutron oscillations with cold neutrons with a novel technique at the Institut Laue Langevin in Grenoble, and for νμ → ντ oscillation with a huge detector in a large collaboration (NOMAD) at CERN, where she led the Italian contingent. In both cases, the experiments obtained important upper limits. Having supported from the start the ICARUS detector for the study of solar neutrinos and of nucleon stability, in recent years she invested much effort to have the detector working in the Gran Sasso Laboratory: the experiment is now a reality.

Milla became full professor in 1964 and a few years later was appointed director of the Padua Section of INFN and then became director of the Department of Physics. She was a member of several academies and was awarded the Feltrinelli Prize by the Accademia dei Lincei, as well as the Gold Medal for Education and Arts, the Gold Medal for Science and the Enrico Fermi Prize from the Italian Physical Society.

In 1988 she started the world-renowned series of Workshops on Neutrino Telescopes at the Instituto Veneto di Scienze, Lettere ed Arti in Venice. These gathered hundreds of scientists to discuss neutrino properties, astrophysics and cosmology; her quest for perfection was manifest both in the scientific programmes and in the cultural and social events.

Milla’s students and colleagues have always been stimulated by her nonconventional approach to scientific, academic and cultural issues. We are grateful to her and will miss her.

Her friends and colleagues in Padua.