Fundamental physics research at the Legnaro Laboratories is also conducted without the use of accelerator machines. Two lines of research in precision physics at high sensitivity are active: the study of neutrinos and search for axions / properties of the vacuum. The final aim for these research fields is a deeper understanding of the connections between some fundamental concepts of quantum and relativistic physics such as mass and energy from the one side, and time and space to the other.
Neutrinoless double beta decay (CUORE and CUPID)
The measurement of the neutrinoless double beta decay is the main task of the experiment CUORE. This measurement would allow us to get detailed information on the properties of the neutrino, one of the fundamental constituents of the Standard Model of particle physics. The apparatus of CUORE is based on a very sensitive temperature detector (bolometer), constituted by ultra pure crystals of tellurium dioxide (TeO2).
The Legnaro laboratories carried out the ultra-cleaning procedure of the copper used to hold the bolometric structure of TeO2, which is now placed in the Gran Sasso Laboratories of INFN. The ultra-cleaning procedure consisted in a sequence of 70 operations for each component, to be done for a total of 4000 pieces. Among the 70 operations of the cleaning protocol, 5 are of paramount importance: mechanical barreling, electrocleaning, chemical attack, passivation, and the final cleaning with vacuum plasma, according to the assumption that “nothing is cleaner than vacuum”.
CUPID is the candidate successor of CUORE, with the introduction of the particle identification; it is under research and development.
Axion research (QUAX) and vacuum properties (PVLAS)
Vacuum is generally defined as a region of space without matter and radiation. In classical physics the empty space has no properties or structures. However, this statement changes in modern physics: the vacuum is the state of minimum energy, and, following from Heisenberg’s uncertainty principle, it must be filled with fluctuations. The vacuum becomes populated with virtual particles: particles that appear and disappear within very short time intervals. Due to the presence of virtual particles, the vacuum has physical properties, which are studied in experiments with LNL staffs (PVLAS). In the PVLAS experiment the effect of a magnetic field on the vacuum is studied: the magnetic field acts on the virtual particles and the vacuum becomes similar to a crystal. A polarized laser beam traversing the magnetized vacuum will then change its polarization state: this can be detected by using a device based on an optical resonant cavity and an ultra high sensitivity polarizer. Such effects are so small that nobody has been able to measure them yet, and the cited experiments are trying to reveal them for the first time.
The search for cosmological axions using magnetized materials (QUAX) is a way to investigate dark matter. The axion can in fact interact with the electrons in a magnetic material immersed in a static magnetic field, and this result in the emission of electromagnetic radiation in the radio frequency range. By using a microwave cavity with very high quality factor and very sensitive radio frequency detectors it would then be possible to collect the emitted radiation and thus obtain information on the properties of the axion dark matter. To avoid the effect of the thermal background the experiment must be conducted at cryogenic temperature. The researcher forming the QUAX collaboration are studying the feasibility of this detection scheme.