Our research is performed within the INFN and the University of Florence. The National Institute for Nuclear Physics (INFN) is the Italian research agency dedicated to studying the fundamental constituents of matter and the laws that govern them, under the supervision of the Ministry of Education, Universities and Research (MIUR). The institute was founded to uphold and develop the scientific tradition established during the 1930s by Enrico Fermi and his school. The University of Florence is an Italian public research university comprising 12 schools and around 50'000 students enrolled. The University was founded in 1859 and recognized as a full-fledged university by the government of newly unified Italy in 1860.

Project funded by INFN CSN5 Grants
Principal investigator: Naomi Marchini

The ARDE project's goal is to conduct a comprehensive investigation into methods for distinguishing between electrons and gamma rays of nuclear origin in semiconductor detectors. The identification and measurement of these electrons, especially their energy determination, hold significant importance in both fundamental and applied physics research. Such studies encompass endeavours like exploring electric monopole transitions between nuclear states, which shed light on quantum phenomena like the coexistence of nuclear shape and nucleosynthesis of elements in stars, or detecting beta particles in radionuclides used for medical applications. One of the primary challenges in these measurements is the background contribution caused by gamma rays emitted during the de-excitation of the nuclear states under examination or due to natural radiation. ARDE aims to investigate techniques to substantially reduce this background in semiconductor electron detectors, mainly Si(Li) detectors, by leveraging signal shape analysis. These techniques will be pioneering the integration of "machine learning" methodologies for gamma-ray and electron discrimination, enabling the simultaneous utilisation of all the information contained in the collected signals. A successful outcome of this project will establish the foundation for similar advancements in the medical field and rare event physics.

Contact: Naomi Marchini (naomi.marchini@fi.infn.it)

Project funded by Italian PRIN - Project of Relevant National Interest
Group principal investigator: Adriana Nannini

The BEGAM project addresses the isotopic purity of radiopharmaceuticals used in medical diagnostics from tomographic and planar imaging techniques. These techniques give the spatial distribution of a molecular probe labelled with a radionuclide and injected into the patient's body. After the injection, the outcoming radioactivity is registered by specific energy and space-sensitive detectors displaced outside the patient's body; for this reason, the use of radionuclides having a gamma emission associated with their beta decay is in order. The aim of BEGAM is the design and implementation of a portable and versatile setup, allowing for the detection of undesired pure beta emitter contaminants (which decay from ground state to ground state) inside the radiopharmaceutical. Such contaminants increase the dose absorbed by the patient, worsen the quality of the obtained image, and cannot be easily identified by employing commonly used dose calibrators.
The project is a collaboration with the Careggi Hospital in Florence, where the radionuclide will be produced at the GE MiniTrace 9.6 MeV cyclotron.

Contact: Adriana Nannini (adriana.nannini@fi.infn.it)

The FAZIA project unites over ten institutions specializing in nuclear physics, actively engaged in the study of heavy-ion-induced reactions near and below the Fermi energy. While the project's primary groups are based in Italy and France, collaboration extends to researchers from Spain, Poland, and South Korea.
The project aims to conduct experiments utilizing a charged particle detector characterized by a wide solid angle coverage, excellent granularity, and high temporal resolution. FAZIA is specifically designed to maximize the isotopic separation of detected ions, employing both stable and radioactive ion beams. This capability facilitates the exploration of the thermodynamics and dynamics of exotic nuclei, delving into the isospin degrees of freedom (linked to the neutron-to-proton ratio) of nuclear matter. Additionally, the project sheds light on their role in the nuclear equation of state under high temperatures and nuclear densities, far from saturation.
Within the Fermi energy range (20-50 MeV/nucleon), a rich phenomenology is observed, ranging from binary reactions in peripheral collisions to multifragmentation events in central collisions. The reaction mechanism is influenced by both mean-field effects and nucleon-nucleon collisions. The theoretical framework predominantly relies on transport models, which have achieved considerable success, yet several crucial aspects still elude a complete modelling description.
The FAZIA project thus serves as a critical platform for experimental and theoretical investigations, pushing the boundaries of our understanding of nuclear matter and providing valuable insights into the complex dynamics of exotic nuclei.

Contacts: Simone Valdré (simone.valdre@fi.infn.it), Giovanni Casini (giovanni.casini@fi.infn.it)

Neutrinoless double-beta decay 0νββ is a speculated, extremely rare nuclear transition, which can only occur if neutrinos are massive Majorana particles. The process violates lepton number conservation and, consequently, is forbidden by the Standard Model. If this decay exists, its observation would shed light on the nature of neutrinos and would open up new physics and pave the way for a possible explanation of the origin of the matter-antimatter asymmetry in the Universe. Accurate knowledge of nuclear structure is essential to calculate the nuclear matrix element (NME) involved in the 0νββ decay. 

Among the nuclei accessible for ββ studies, ¹³⁰Te is an outstanding candidate from the experimental point of view and has been chosen by two international collaborations: CUORE in Italy and SNO+ in Canada. Two different theoretical approaches, such as Beyond-Mean-Field and Shell Model, describe 0νββ as favoured if the shapes of the parent ground state and the daughter state are similar, and the decay rate is further enhanced if both are spherical. However, different theoretical approaches predict different shapes for the states involved in the 0νββ ¹³⁰Te → ¹³⁰Xe decay.

For this reasons, we started a campaign to extract experimentally the shape of the states involved in the 0νββ ¹³⁰Te → ¹³⁰Xe decay, and particularly to investigate the impact that the phenomenon of shape coexistence might have in the decay. In order to achieve our goals, experiments have been performed using the low-energy Coulomb excitation technique and complementary methods at the INFN-LNL (Italy), TRIUMF (Canada), ANL (US), and MLL (Germany) laboratories.

Contact: Marco Rocchini (marco.rocchini@fi.infn.it)

Recent advancements in High-Purity Germanium (HPGe) detectors and facilities for Radioactive Ion Beams (RIBs) production and acceleration provide access to the most exotic regions of the nuclide chart. Several intriguing phenomena related to the structure of nuclear matter have been discovered in these years, and our knowledge of the nucleon-nucleon interaction - and therefore the strong interaction - improves continuously. However, additional devices are needed to fully exploit the capabilities of these new technologies and apply specific nuclear spectroscopy techniques. In this project, we develop new detectors and devices that are mainly designed for RIB experiments but can be used also for stable beam experiments.

In the framework of the INFN facility for RIB production and acceleration, SPES, we developed a segmented silicon detector for heavy ions, SPIDER. The detector has been already used in many experiments with stable beams at the INFN-LNL laboratories, coupled with the GALILEO and AGATA HPGe arrays. It is mainly designed for the low-energy Coulomb excitation technique but it has also been used for experiments exploiting other kinds of reactions.

Another development we are working on is SLICES, an innovative spectrometer for internal conversion electrons. The instrument has been designed to be used at the beta-decay station of SPES. It is based on the use of a custom-made, large-area segmented Si(Li) detector, coupled to a system of magnetic lenses.
The first RIBs from SPES are expected for 2024-2025. SPIDER and SLICES will be among the first instruments to be used in the experimental campaigns.

Contact: Adriana Nannini (adriana.nannini@fi.infn.it)

This project focuses on unravelling the intricate phenomenon of nuclear clustering within atomic nuclei. Nuclear clusters, where nucleons organize into distinct groups, present a complex puzzle that transcends mass regions and isotope chains. An international collaboration of physicists, spanning various institutions, converges to explore the conditions and characteristics of clustered nuclear configurations through cutting-edge experimental techniques.
Diving into the heart of this mystery, researchers investigate diverse manifestations of clustering, ranging from alpha-like configurations in lighter nuclei to intricate structures in heavier isotopes. Advanced detectors and innovative methodologies are employed to discern the specific dynamics that give rise to these clustered formations.
Theoretical models, grounded in quantum mechanics and nuclear forces, play a pivotal role in interpreting experimental data, striving to capture the nuances of stability and energetics inherent in clustered configurations. The project not only refines existing models but also pioneers novel approaches to comprehensively understand the rich landscape of nuclear clustering.
Beyond contributing to fundamental nuclear structure knowledge, this research carries implications for astrophysical phenomena, such as nucleosynthesis in stellar environments. The exploration of nuclear clustering dynamics sheds light on the intricate interplay between nuclear forces, shell structure, and clustering phenomena, propelling advancements in our comprehension of the diverse and dynamic nature of atomic nuclei.

Contact: Alberto Camaiani (alberto.camaiani@fi.infn.it)

The structure of neutron-rich nuclei of mass around 100 provides some of the best examples of the interplay between microscopic and macroscopic effects in the many-body nuclear system. Here, collectivity rapidly evolves as a function of Z and N, with evidence of shape coexistence built on different configurations.

State-of-the-art Monte Carlo Shell Model calculations explained the presence of multiple shapes at low energy in the zirconium isotopic chain due to the interplay between the so-called type-I and type-II shell evolution. Type-I consists of a re-organization of the shell structure of the nucleus when adding neutrons to the system. Single particle energy can change with the different orbitals being occupied, producing different configurations with respect to the ground state with unique shapes. In type-II shell evolution, the mechanism is the same but particle excitations give the different occupations, within the same nucleus.

This interpretation also has consequences for quantum systems beyond the nucleus. Indeed, the dramatic change in the ground state shape when moving from ⁹⁸Zr to ¹⁰⁰Zr would represent a quantum phase transition where the control parameter is the number of neutrons and the macroscopic quantity that changes is the shape. Also, the stability of shape-coexisting configurations within the same nucleus might be due to a phenomenon very similar to the so-called self-organization already observed in many other fields of physics and chemistry, biology, robotics, and social sciences.

While this explanation is supported by an excellent reproduction of some nuclear properties, the shapes of the low-lying states in zirconium isotopes remain unknown. Therefore, within this project, we aim at a detailed characterization of shapes and mixing of low-lying states in zirconium isotopes using low-energy Coulomb excitation and complementary techniques. For this project, we performed experiments at the INFN-LNL (Italy), TRIUMF (Canada) and MLL (Germany) laboratories.

Contacts: Naomi Marchini (naomi.marchini@fi.infn.it), Marco Rocchini (marco.rocchini@fi.infn.it)