The research in nuclear physics aims to explore the properties of sub-atomic matter and in particular to study the property of nuclei, the core of atoms where about 99% of the visible Universe is enclosed. Nuclei are very complex objects consisting of protons and neutrons, the fundamental constituents of all the matter that surrounds us, which interact with each other through nuclear forces whose nature and characteristics are not known in detail. They represent the fundamental topic of research in nuclear physics.
To study the properties of this microscopic world, physicists have developed particle accelerators that allow, through the collision between the accelerated nuclei of the beam and those of the target to "see" the nuclei and study their properties.
The Laboratori Nazionali del Sud (LNS) are equipped with two particle accelerators, the TANDEM and the Superconducting Cyclotron which are used to accelerate ions with a mass between the proton and lead and try to find answers to some of the fundamental questions of modern nuclear physics, including:
- How are the elements synthesized in the stars?
- How is matter organized on the sub-atomic scale and what phenomena arise?
- Which combinations of protons and neutrons give life to a bound system and why?
- What is the maximum thermal energy that a nucleus can sustain before fragmenting?
The research activities are carried out by the various experimental groups of the LNS using experimental equipment designed and developed for the study of specific topics in nuclear physics. The topics of the research carried out at the LNS concern nuclear astrophysics, nuclear structure and reaction mechanisms, phase transition of nuclear matter, quarks and hadron dynamics.
The role of nuclear physics will grow over the next few years thanks to upgrades underway, which include increasing the intensity extracted from the superconducting cyclotron and installing a new magnetic separator for the production of radioactive nuclei.
The study of the dynamics and quark structure of the constituents of the nucleus represents the research objective of the JLAB12 experiment
JLAB12 is an experiment that uses a high-energy electron beam (about 10 GeV) produced by the Jefferson Laboratory accelerator in Virginia (USA) to study the dynamics and internal structure of nucleons and nuclei by electron diffusion. Other research topics concern the study of physics beyond the standard model and the dark matter of which we know very little. The activities of the LNS, carried out by a research group from Sassari, focus on the HPS experiment that aims to find the traces of the so-called "dark photon" or "heavy photon", a massive photon whose detection would be a first sign of the existence of a hidden world.
The study of the phase transition of nuclear matter is one of the main research topics of the CHIRONE experiment
CHIRONE uses the high granularity of the CHIMERA detector and its capabilities in identifying the mass and charge of reaction products to study the effects of isospin (a quantum number associated with the ratio between the number of neutrons and protons in the nucleus) on the reaction mechanism and the density dependence of the symmetry term of the nuclear matter equation of state. Other research topics concern the study of the cluster structure in exotic nuclei and that of the "pygmy resonances", manifestations of a particular collective nuclear motion, which are carried out using the exotic beams produced by fragmentation (FRIBS, and in the near future, FRAISE), at the LNS.
From nuclear physics to particle physics: the NUMEN experiment
The activity of NUMEN is focused on the study of double-charge-exchange reactions carried out mainly through the MAGNEX spectrometer. The main aim of the studies is to measure the nuclear matrix elements of interest for double beta decay without neutrino emission, an extremely rare decay whose observation would allow the neutrino to be identified as a Majorana particle, i.e. as a particle that coincides with its antiparticle, the antineutrino. NUMEN also aims to identify the best candidate nuclei for double beta decay experiments without neutrino emission.
Nuclear astrophysics with indirect methods: the ASFIN2 experiment
Researchers from the ASFIN2 group are involved in the study of the reaction cross sections of the processes that influence stellar evolution and are fundamental for the primordial nucleosynthesis. For this purpose, they use low energy reactions (typically using TANDEM beams) and new techniques that use high-power lasers to produce plasmas to simulate the conditions at which reactions occur in astrophysical contexts. The research is carried out using the so-called "indirect methods" among which the most used is the Trojan Horse. Furthermore, ASFIN2 deals with the study of the effects of nuclear structure on astrophysics. For this purpose, experimental techniques (such as resonant scatterin) and innovative detectors (for example the SOLE superconducting solenoid) are used to investigate nuclear cluster structures or the presence of neutron halos in light nuclei, as well as nuclear collective motions, such as the giant dipole resonance or the dynamic dipole.
Between nuclear astrophysics and applied physics: the n_TOF experiment
The experimental activity of the n_TOF group takes place at CERN and uses high intensity neutron beams (up to 106 neutrons / cm2 per pulse) and energies between 25 meV and 1 GeV that allow the measurement of cross sections, also very low, of the processes involving neutrons interaction with matter and the study of the implications on the synthesis of light elements following the Big Bang. Furthermore, neutron beams are used in the study of uranium fission due to its importance in applications.
PANDORA: a new experiment to study β decays in magnetized plasmas
The PANDORA experiment is based on a magnetic trap capable of confining plasmas at high temperatures (up to 108 K) and densities of the order of 1013 cm-3, containing multi-ionized radioactive isotopes to study the β-decay under astrophysical conditions (for example, for the elements involved in the "s" process of stellar nucleosynthesis). This variation, predicted theoretically (bound-state β decay) and preliminarily observed in a small number of isotopes under conditions of maximum ionization (in an experiment on the Storage Ring of the GSI, carried out on the completely ionized 187Re, the average life has collapsed by 9 orders of magnitude), has never been investigated and measured in plasma.