Neutrino Physics

The neutrino group at IKP-2, formed by the recruitment initiative of the Helmholtz Association, is studying the low-energy neutrino physics based on the liquid scintillator detection technique. Along with many international collaborators, the group is participating in the Borexino/SOX (Italy) and JUNO (China) experiments. Besides expanding our fundamental knowledge about particle physics by searching for sterile neutrinos and determining the neutrino mass hierarchy, the topics of interest of these experiments include using neutrinos as a unique source of information about processes in the Earth and the Sun.

Borexino

Borexino is a 300 ton liquid scintillator detector placed at the Laboratori Nazionali del Gran Sasso (LNGS), the largest underground laboratory in the world. Coverage by the 1400 m thick rock provides a cosmic-ray-flux reduction by one million times.

The Borexino collaboration's primary goal is detecting solar neutrinos, particularly those below 2 MeV. The experiment’s distinctive feature is the unprecedented ultra-low radioactive background, which is the basis of the outstanding achievements obtained by the experiment.

The most important results concerning solar neutrinos include:

• the first real-time measurement of neutrinos from the primary proton–proton fusion process in the Sun.

• the measurement of 7Be solar neutrinos with 5% precision;

• the first direct observation of the pep neutrinos;

• the best available upper limit on the flux of solar neutrinos produced in the CNO (carbon, nitrogen, oxygen) cycle;

In 2010 the Borexino collaboration reported the first observation of geoneutrinos at more than 3σC.L. Geoneutrinos, antineutrinos emitted along the U and Th decay chains, hold clues about the Earth radiogenic heat. Its more precise determination would bring precious insights about the formation, composition, and dynamics of our planet. Borexino, together with KamLAND in Japan, are the only two experiments being currently able to measure geoneutrinos.

SOX

Short-distance neutrino Oscillation with BoreXino, the SOXproject, aims at the complete confirmation or at a clear disproof of the existence of a light sterile neutrino. It is called sterile because it would not interact through the forces described by the Standard Model. A global analysis of short-baseline neutrino oscillation data in 3+1 parameter space leads to Δm214around 1 eV2. In order to probe this region with MeV (anti)neutrinos, the oscillation experiments at distances of few meters have to be performed. In such an experiment, the hypothetical existence of sterile neutrino could be observed not only through an absolute disappearance, but also through the oscillation pattern in (L, E) parameter space deviating from the standard 3-flavour scenario. That latter would provide a "smoking gun" signature of the sterile neutrino, a clear indication for physics beyond the Standard Model.

JUNO

The Jiangmen Underground Neutrino Observatory (JUNO) is a neutrino experiment under construction near Jiangmen, China. Its main component is a spherical 20 kiloton liquid scintillator detector in a 700 m deep underground laboratory, characterised by an unprecedented 3% at 1 MeV energy resolution. The experiment is designed for the determination of the neutrino mass hierarchy by measuring oscillation effects of neutrinos from two nearby nuclear power plants at 53 km baseline. In addition to that JUNO has the potential to increase the precision of already measured oscillation parameters and it can give a major contribution in the field of geoneutrinos. Astrophysical measurements of solar and supernova neutrinos are also part of the physics programme.

Local contact persons in IKP-2:



Prof. Dr. Livia Ludhova