1. Research project objectives/ Research hypothesis

The scientific goal of this project is the search for signals on non-standard particle physics by looking for neutrino oscillations into sterile neutrinos. It is proposed to realize an experiment sensitive to a large fraction of the parameter space for short distance neutrino flavor oscillations into sterile components. The experiment, named SOX (Short distance Oscillations with boreXino), aims at the complete confirmation or at a clear disproof of the so called neutrino anomalies, a set of circumstantial evidences of electron neutrino disappearance observed at LSND, MiniBoone, with nuclear reactors and with solar neutrino Gallium detectors. The SOX project has been awarded by ERC Advanced Grant (Project Reference: 320873).

If new generations of particles do exist, it is plausible that new neutrino species exist as well, and mixing with known active neutrinos might occur. This scenario, though speculative, is supported by a set of non-conclusive but very significant experimental evidences coming both from particle physics and from cosmology. On one side, several experiments probing neutrino and anti-neutrino oscillations at relatively small values of L/E have observed a systematic lack of events in their detectors, a fact which might be explained in terms of neutrino oscillations into an unknown very weakly interacting component. On the other side, Cosmic Microwave Background Radiation (CMBR) experiments and Large Scale Structure (LSS) studies, when interpreted in the framework of standard cosmology, indicate that the total number of neutrinos in the Universe might be bigger than three.

2. Research project methodology

The BOREXINO detector, originally designed for precision study of low energy solar neutrinos and for the detection of anti-neutrinos originating from the Earth or from unknown astrophysical sources, is an ideal apparatus for the search of sterile neutrinos, both in neutrino and anti-neutrino mode. The experiment will be done by placing a well-designed artificial neutrino sources (⁵¹Cr, ¹⁴⁴Ce-¹⁴⁴Pr) close or inside the BOREXINO solar neutrino detector at the Laboratori Nazionali del Gran Sasso. The superb BOREXINO sensitivity, its large size, and very low radioactive background will be the key elements of the experiment. The well proved capability to detect both low energy electron neutrinos and anti-neutrinos make an ideal case for the study of short distance neutrino oscillations with artificial sources. ⁵¹Cr decays via electron capture into ⁵¹V, emitting two neutrino lines of 750 keV (90%) and 430 keV (10%), while ¹⁴⁴Pr decays β into ¹⁴⁴Nd with an end-point of 3 MeV. SOX will yield additional physics. The electroweak angle θ_W can be directly measured at MeV scale from the ν_e-e⁻ cross-section with an expected precision of 2.6%.

3. Expected impact of the research project on the development of science, civilization and society

SOX project has the potential to discover hypothetical sterile neutrinos. The discovery of the fourth family of neutrinos may be of fundamental importance for the theory of particles and for cosmological models. The precise measurements of the electroweak theory parameters at low energies will be performed.

Physics Letters B
Volume 713, Issue 3, 9 July 2012, Pages 258–263

Download: http://www.sciencedirect.com/science/article/pii/S037026931200634X

Abstract
In this Letter, we indicate the possibility of using the decay of polarized muons at rest (DPMaR) as a source of the transversely polarized electron antineutrino beam. Such a beam could be used to probe new effects beyond standard model such as: time reversal violation, existence of right-chirality (anti)neutrinos. The (anti)neutrinos are assumed to be Dirac fermions with non-zero mass. We analyze a scenario with the participation of the complex exotic vector, scalar and tensor couplings of the right-chirality electron antineutrinos in addition to the standard vector coupling of the left-chirality ones. We show that the energy–angle distribution of the electron antineutrinos from the DPMaR depends on the interference terms between standard and exotic couplings, which are proportional to the transverse components of the antineutrino spin polarization and independent of a antineutrino mass. It allows to calculate the flux of electron antineutrinos and the expected number of recoil electrons in the elastic antineutrino–electron scattering ve, where the incoming antineutrino beam comes from the DPMaR and is transversely polarized. Our analysis is model-independent and consistent with the current upper limits on the non-standard couplings. The results are presented in a limit of infinitesimally small mass for all particles produced in the muon decay.