by Virginia Greco. Published: 11 June 2018

Renato Angelo Ricci, who is still an active member of the ALICE Collaboration at the age of almost 91, is a brilliant physicist and he is the most senior affiliate of the Italian National Institute of Nuclear Physics (INFN) and of the Italian Physical Society (SIF). In this interview, we retraced with him the various phases of his excellent career.

On his way to turn 91, Renato Angelo Ricci is not only a distinguished physicist, but also the dean of the members of the Italian National Institute of Nuclear Physics (INFN) and of the Italian Physical Society (SIF), as well as the most veteran active member of the ALICE Collaboration.

After graduating in physics in 1950 at the University of Pisa (Italy) and completing his proficiency courses at the Scuola Normale Superiore in 1951, he continued his studies in atomic and nuclear physics in Paris, at the École Polytechnique and the Collège de France, as a student of Nobel Laureates Louis de Broglie and Frederic Joliot Curie.

An extraordinary career followed, which led Ricci to become a pioneer of nuclear spectroscopy and heavy-ion physics in Italy, to make relevant contributions to nuclear physics and to cover very important positions.

We recalled with him the different phases of his career in this interview.

 

Professor Ricci, you have had a brilliant career, which started with excellent studies and continued with important collaborations and prestigious assignments. I would like to retrace with you the fundamental stages of it, starting from the attendance of the Scuola Normale di Pisa and your training as a student of Nobel Laureates Louis de Broglie and Frederic Joliot Curie. Can you tell us about these experiences?

I attended the University and the Scuola Normale of Pisa in the immediate post-war years, between 1945 and 1950. That was a hard and peculiar period. During the war, I had been forced to interrupt my studies at the scientific Liceo in La Spezia, the town where my family lived, because of the bombing, the consequent displacement, as well as my father’s and my participation in the resistance as partisan support. After Italy was liberated, I I completed my high school years and, on the advice of my professors, I took part in the competition to enter the Scuola Normale. I was admitted and I enrolled at the Faculty of Physics.

My original intention was to switch to Engineering after the first 2 years of Physics, in view of a more profitable degree, since I felt obliged to help my family. But the cultural atmosphere I was immersed in and the incentives to study that I received by encountering excellent teachers and colleagues – many of them sons of railwaymen as myself – helped me to realize that physics was more up my alley. Not only did I find it thrilling, but it also opened up scientific and humanistic horizons that were congenial to me. Furthermore, in those years, physics was having a great development in various fields: atomic and nuclear physics, the theory of relativity, quantum mechanics, cosmic radiations, the field theory, etc.

When I was at my third year at the Scuola Normale, I was required to develop a physics topic of my choice and give a seminar on it: I opted for the theory of relativity, focusing particularly on Minkowsky space-time. It was a success and, indeed, I graduated cum laude in Theoretical Physics in 1950, discussing a thesis in atomic physics, which I developed under the supervision of Tullio De Renzini. Then, thanks to a scholarship provided by the Scuola Normale, I moved to Paris to complete my specialization, first at the École Polytechnique as a student of Louis DeBroglie and then at the Collège de France under the guidance of Fréderic Joliot-Curie. This explains my jump from theoretical to experimental physics: I got convinced that I had a more phenomenological vocation, even though enriched by a deep theoretical knowledge.

Back in Pisa, where I was given an assignment as an Assistant Professor at the University, I improved my knowledge of cosmic ray physics with Marcello Conversi, who supervised my work for the Scuola Normale proficiency thesis on the "Energy component of cosmic rays".

I admit that I haven’t ever had a real mentor of whom becoming an assistant and that could secure my scientific career. What I did was looking by myself for teachers and brilliant scientists I could learn from.

After dedicating a substantial part of your scientific activity to the study of the physics of nuclei – their structure and dynamics –, you moved on to work on relativistic heavy-ion physics. How did this evolution happen?

Indeed, between 1952 and 1990, I dedicated my time mainly to specific and systematic studies of the phenomenology of atomic nuclei, to the point that I am considered the father of Nuclear Spectroscopy in Italy.

In 1952, I left Pisa for a position at the Polytechnic University of Turin. There, as an assistant of Eligio Perucca, I started my research on radioactive decays of heavy nuclei of the radon family using scintillation techniques, which had been just introduced, and I became an expert in this topic. In that period, I entered in touch with the Dutch group working in this field (led by A.H. Wapstra and R. Van Lieshout), which would soon become a reference point for gamma spectroscopy and analysis techniques for nuclear decays, and I went to spend two years in Amsterdam to collaborate with them. This was a very fruitful experience! As soon as I returned to Italy, I started nuclear spectroscopy in Naples, at the forthcoming section of the National Institute of Nuclear Physics (INFN), where prominent physicists such as Edoardo Caianiello and Giulio Cortini were very interested in supporting this branch of research.

In Naples, I carried out my studies employing the gamma spectrometry techniques I had introduced and a 400 keV Van de Graaff accelerator, which allowed producing 14 MeV neutrons. The latter could be used for reactions suitable to generate radioactive isotopes, the decay and spectroscopic properties of which we wanted to investigate. I also collaborated with the Munich research group led by Haruhiko Morinaga in the exploration of important properties (shell-model and collective states) of medium-mass nuclei, made possible by the use of a Tandem accelerator for heavy ions. It was an intense period that brought about excellent results.

I continued these activities in Florence, where I became tenured professor, and then in Padua and Legnaro, where the INFN National Laboratories were being established as part of the institute national strategy (promoted by Antonio Rostagni and Claudio Villi) with the support of the INFN Presidents (Eduardo Amaldi and Giorgio Salvini).

With the installation in Legnaro, under my direction, of the first 16 MeV Tandem accelerator, Italy could actively take part in the heavy-ion physics research programme. The following installation of the ALPI superconducting linear accelerator allowed – coupled with the Tandem – to operate at higher energies (hundreds of MeV / nucleon).

In the 80s, INFN opened up to more extensive collaborations and activities at CERN in the field of nuclear physics. I sponsored this operation as a Chairman of the INFN Nuclear Physics Committee and I formed a group in Legnaro to work with the OBELIX collaboration using the antiprotons delivered by the CERN LEAR. I also was among the promoters of a significant commitment in the field of physics of relativistic heavy ions, with the particular objective of investigating nuclear matter in extreme conditions of energy density to obtain information on the possible deconfinement of the quark-gluon plasma (QGP). Dedicated research groups were formed in Padua and Legnaro, to work on the NA57 and WA97 experiments at the SPS and, later, on ALICE at the LHC. In this regard, I would like to mention the important contribution of Maurizio Morando, the late Luigi Vannucci and Giuseppe Viesti, as well as – of course – of Federico Antinori and Andrea Dainese. The Legnaro team actually contributed to the installation of the radiofrequency cavity (RFQ) in the heavy ion beam line for the SPS.

What are your contributions to physics research that you consider as the most relevant, or the accomplishments of which you are particularly proud?

Considering the various aspects of the research in which I participated, I would distinguish the contributions that are strictly scientific from the promotional ones.

In the first group, I would include the discovery of new radioactive isotopes and new isomeric states, the study of the isobaric invariance in nuclear physics and of the magnetic dipole effects in single particle configurations of heavy nuclei, the observation of the decaying scheme of Titanium-50 and its two-body spectrum (two-protons) identical to that of two-neutrons, which was essential to determine the charge-independence of effective nuclear forces in a given nuclear shell. In fact, the particular shell-model configuration of the f7/2quantum orbital was studied in a systematic way by our collaboration (Legnaro-Padova-Florence-Munich) for several years, with the result of establishing the coexistence of shell-model and collective states. Important results were also obtained in 1964 at the 155 MeV proton Synchrocyclotron in Orsay, in collaboration with the group led by Michel Riou, performing inelastic proton scattering and (p,2p) knock-out reactions: we could identify clear collective states and demonstrate the existence of shell-model orbitals. Another pioneering work carried out by the Padova-Napoli-Trieste group at the Legnaro Van de Graaff accelerator led to the finding of isobaric analogue resonances with fine structure in that nuclear region. Hence, the ‘f7/2’ symbol was considered as a ‘trade mark’ of our scientific activity and indeed the Symposium organized for my 80th birthday was titled: ‘From f7/2 nuclei to the Quark-Gluon Plasma’.

Other results obtained with the Legnaro Tandem experiment concern the dynamics of reactions induced by heavy ions and, in particular, the existence of intermediate processes between evaporation and fission, in the dissipative reactions.

As for the activity at CERN, I think I have contributed to some interesting results in the OBELIX experiment, including the identification of new mesonic resonances. Then, in the field of relativistic heavy ions, I would mention the contributions of the Padova-Legnaro group to the measurements with sulfur and lead ions, performed at the NA57 and WA97 experiments, that provided the evidence of strange particle production, first indicators of presence of the QGP.

Moving on to ALICE, in addition to contributing to its promotion and its design phase, I played my part of (as?) consultant, participating in the definition of its physics programme.

Among the numerous studies that ALICE can perform, there are two that I consider particularly interesting. One is the measurement of the production of light anti-nuclei (and anti-hypernuclei), which provides a test of unprecedented precision of the CPT invariance. The latest result in this field concerns the production of anti-alpha, the heaviest antimatter nucleus observed so far. The other one is the study of the abundance of strange particle production that has been observed in the high multiplicity proton-proton collisions. This odd result, besides being intriguing for the insights that provides into the collective effects in interactions between protons and not only between complex nuclei, would indicate that the behaviour of QGP has to do in a decisive way, microscopically speaking, with the multiplicity of the particles produced.

In general, I must say that for me, a physicist coming from small research groups in which everything was almost hand-crafted, being part of big CERN collaborations has been not only interesting and gratifying, but also educational. In our field, having a collaborative spirit – and possibly a certain degree of cultural humility – becomes essential; the success of the individual is ‘glory for all’. Thus, I want to address my best wishes to the young researchers in ALICE for their future and thank the whole collaboration for making me feel welcome and respected.

In 2014, on the occasion of the 100th SIF National Convention, Ricci received a medal as Honorary President of the SIF, presented to him by Luisa Cifarelli.

 

As already mentioned, you have also held numerous important positions, such as that of Director of the INFN National Laboratories of Legnaro, President of the Italian Physical Society (SIF), President of the European Physical Society (EPS) and so on. Would you recall for us these stages of your career?

I think that this kind of appointments are part of our job and they produce effective results if taken in due course and with a serious assumption of responsibility. They are not specific stages of one’s career, at least they were not for me. I was elected President of SIF in 1981, so I resigned from my position as Deputy President of the INFN, to which I had been elected in turn after being Director of the National Laboratories of Legnaro (1968-1979). The Presidency of the SIF lasted 17 years, up to 1998, due to subsequent re-elections.

I was also President of the EPS from 1989 to 1991. In that capacity, I had the privilege to inaugurate the unification of the West and East German Physical Societies, a year before the fall of the Berlin Wall.

I felt the operational and representative responsibilities of these assignments, so I have always tried to be worthy of the trust of my colleagues. I believe that, on the one hand, I contributed to enhance the cultural and social presence of a glorious scientific society as SIF, and, on the other hand, I did my best as Director of the Laboratories of Legnaro. In those years, they succeeded first to establish themselves at the national level as a centre for nuclear physics research and then, with the advent of the accelerator for heavy ions, to become one of the most accredited facilities internationally.

I was also very happy that, as a consequence, I was asked by the Italian Encyclopaedic Institute “Treccani” to cure the entries of Nuclear Physics of the Encyclopaedia of Physical Sciences published in 1993. I must also add that the role of Chairman of the INFN Committee for the Physics of the Nuclei was not of minor importance and satisfaction.

All of this, of course, involved not only honours, but also problems and difficulties, as well as tiredness, errors and sometimes misunderstandings. Nevertheless, from my point of view, the balance has been positive and I hope that some message was picked up by the younger people who followed me.

What is your vision of the future of heavy ion physics?

I think that significant results will be achieved in the next years both in the processes at low and medium energies and in those at very high (relativistic) energies.

In the field of atomic nuclei structure and dynamics, the possibility of accelerating beams of radioactive nuclei and the extensive use of gamma spectroscopy with increasingly sophisticated detectors (which allow high efficiency and resolution) will undoubtedly provide results related to exotic nuclei and new types of configurations, at higher excitation energies.

In turn, high-energy collisions of relativistic heavy ions can give a strong contribution to understanding the properties of the primordial matter and its evolution. In particular, they can provide both stronger evidence of the identification of the QGP and a plethora of new phenomenological results, hopefully even unexpected, coming not only from the study of the Pb-Pb collisions, but also of the p-PB and pp events. Indeed, such phenomenology, characterized by an unprecedented accumulation of temperature and energy density, is very peculiar and almost unique: every event is almost a big bang on a microscopic scale.

In any case, as theorist Freeman Dyson advices: ‘The best way to know the future of physics is to stay alive as much as possible.

In addition to being the most veteran active member of the ALICE collaboration, you are also the dean of INFN and SIF physicists. What drives you to continue working and moving into the scientific arena?

On the one hand, being the dean of Italian physics is certainly gratifying since I still can follow what is happening and participate with useful opinions and suggestions; on the other hand, however, it involves the feeling of being a survivor – even if meant in self-ironic terms – because I know I am a spectator more than an actor. This is also accompanied by sadness, caused by the memory of those former students and younger collaborators who have already departed.

Anyway, I cannot really say that I am active in the scientific arena: I certainly am so consciously and intellectually, but not much practically.

Last year, I was invited to give a seminar at the Course of Nuclear Physics of the International School of Physics "E. Fermi" of SIF, on the occasion of my reaching the age of 90. In that talk, which I titled "65 years with Nuclear Physics", I retraced my entire career. What’s next? Again, the best way to know the future is to stay alive as much as possible.

What are your passions and interests outside physics?

I have had and still have many, indeed! I love sport – I practiced a bit of athletics when I was young – and classical music, a passion that was transmitted to me by my wife Claudine. I owe so much to her: I have shared with her 65 years of common life (as with physics) and the love for our family and children.

I am also passionate about great literature, painting – even the abstract one, although I do not fall for certain abstruse and illusory forms of contemporary art –, philosophy and history of science. At the moment, I would like to find time to write. I have ideas, but I wonder whether it is too late... Along my life I have actually written many things, from articles and reports to essays and even poems, but never a full book. Although I have always provided my students with very detailed and complete lecture notes. We will see if I manage to write a book. I will try to follow Dyson's suggestion for this as well.