The accelerator of the LUNA experiment
There is a key process – in the sequence of reactions known as Big Bang Nucleosynthesis – that led to the production of the lightest chemical elements in the first moments of life of our universe: it is the reaction by which a proton and a nucleus of deuterium fuse together to form the stable isotope of Helium, called Helium-3.
This reaction has now been studied with unprecedented precision at LUNA (Laboratory for Underground Nuclear Astrophysics), at the Gran Sasso National Laboratories of the INFN. Thanks to this study, it has been possible to refine the calculations of the primordial nucleosynthesis and to obtain an accurate determination of the density of ordinary (or “baryonic”) matter, which makes up everything we know of, including living species.
The results of the measurement conducted by the LUNA Collaboration, and their cosmological impact were published today in the journal Nature.
LUNA is an international collaboration of about 50 scientists from Italy, Germany, Hungary and the United Kingdom. The list of collaborating institutions includes: the National Laboratories of Gran Sasso, the INFN sections and the Universities of Bari, Genova, Milano Statale, Napoli Federico II, Padova, Roma La Sapienza, Torino, and the INAF Observatory of Teramo (Italy); the Helmholtz-Zentrum Dresden-Rossendorf (Germany), the MTA-ATOMKI in Debrecen and the Konkoly Observatory of the Hungarian Science Academy of Budapest (Hungary); and the School of Physics and Astronomy of the University of Edinburgh (United Kingdom).
During their lifetime, stars convert light chemical elements into heavier ones through nuclear fusion processes. However, not all chemical elements are produced in the stars: protons and neutrons, which form the building blocks of all elements, were created in the very first moments of existence of our universe. About 3 minutes after the Big Bang, the temperature of the universe dropped to one billion degrees and deuterium could finally be produced by the fusion of protons and neutrons, without being destroyed by high-energy photons. That was the beginning of the synthesis of light elements, known as primordial nucleosynthesis.
In the cosmic silence of the underground Laboratories of Gran Sasso, where 1400 m of rock protect the experimental halls from external radiation, the LUNA experiment is able to recreate the processes that occurred during primordial nucleosynthesis and that still occur in stars today. With the LUNA accelerator we have brought the clock back in time to a few minutes after the birth of our Universe. The abundance of primordial deuterium is mainly controlled by the fusion reaction studied at LUNA during extensive experimental campaigns. The density of baryon matter obtained through our LUNA results is in excellent agreement with the value inferred from the study of the cosmic background radiation, the "fossil" residue of the Big Bang.
Prof Alessandra Guglielmetti and her team at Milano University and INFN Milano collaborate to the LUNA experiment since 1998. In particular, Guglielmetti has been spokesperson from 2009 to 2015 and is the Principal Investigator of the special project LUNA MV, financed by Italian Ministry of University and Research. LUNA MV will increase the capabilities of LUNA allowing to study key processes for understanding the chemical evolution of the Universe and the nucleosynthesis of the heavier elements.
For further info:
Prof.ssa Alessandra Guglielmetti, This email address is being protected from spambots. You need JavaScript enabled to view it.mi.infn.it