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Borexino has been a neutrino detector based on ultrapure liquid scintillator, located at the Laboratori Nazionali del Gran Sasso, Italy. Its main scientific goal was the real-time measurement of solar neutrino fluxes, which play an irreplaceable role for the comprehension of the mechanisms powering our star. Over the past two years, the Borexino collaboration has pursued the improvement of the CNO flux measurement, obtaining further indications about the solar metallicity. In a parallel way, Borexino has demonstrated for the first time the possibility of exploiting the directional Cherenkov information, in a liquid scintillator detector, for the detection of sub-MeV solar neutrinos.

In the VIP (VIolation of Pauli exclusion principle) and its follow-up VIP- 2 experiments at the Laboratori Nazionali del Gran Sasso, we test the validity of the Pauli Exclusion Principle, by searching for x-rays from copper atomic transitions from a 2p orbit electron to the ground state which is already occupied by two electrons. Such transitions are prohibited by the Pauli Exclusion Principle. The physics run of the VIP-2 experiment started in late 2016 and will collect data for three years. From the first data taking period of two months we have obtained a new limit better than the VIP result from three years of running. In this article we present the published first physics result from the VIP-2 experiment and discuss about the future perspectives.

Borexino is a liquid scintillator detector sited underground in the Laboratori Nazionali del Gran Sasso (Italy). Its physics program, until the end of this year, is focussed on the study of solar neutrinos, in particular from the Beryllium, pp, pep and CNO fusion reactions. Knowing the reaction chains in the sun provides insights towards physics disciplines such as astrophysics (star physics, star formation, etc.), astroparticle and particle physics. Phase II started in 2011 and its aim is to improve the phase I results, in particular the measurements of the neutrino fluxes from the pep and CNO processes. By the end of this year, data taking from the sun will be over and a new project is scheduled to launch: Short distance Oscillation with boreXino (SOX), which uses a Cerium source for neutrinos (100÷150 kCi of activity) and aims to confirm or rule out the presence of sterile neutrinos. This particle is hypothesised to justify the reactor, Gallium and LSND anomalies found and can reject extensions to the standard model. The work presented is a summary of the solar neutrino results achieved so far, which lead not only to a precise study of the processes in the sun, but also to more Standard Model oriented measurements (such as the stability of the charge, i.e. the life time of the electron). Furthermore, the perspectives of the SOX program are discussed showing the experiment sensitivity to a fourth neutrino state covering almost entirely 3σ of the preferred region of the anomalous neutrino experiments, and additional applications of the detector such as the study of geo-neutrinos.

The Borexino detector has convincingly shown its outstanding performances in the low energy, sub-MeV regime through its unprecedented accomplishments in the solar and geo-neutrinos detection. These performances make it the ideal tool to accomplish a state-of-the-art experiment able to test unambiguously the long-standing issue of the existence of a sterile neutrino, as suggested by the several anomalous results accumulated over the past two decades, i.e. the outputs of the LSND and Miniboone experiments, the results of the source calibration of the two Gallium solar neutrino experiments, and the recently hinted reactor anomaly. The SOX project will exploit two sources, based on Chromium and Cerium, respectively, which deployed under the experiment, in a location foreseen on purpose at the time of the construction of the detector, will emit two intense beams of neutrinos (Cr) and anti-neutrinos (Ce). Interacting in the active volume of the liquid scintillator, each beam would create an unmistakable spatial wave pattern in case of oscillation of the νe (or ν̅e) into the sterile state: such a pattern would be the smoking gun proving the existence of the new sterile member of the neutrino family. Otherwise, its absence will allow setting a very stringent limit on its existence.

Solar neutrinos have been pivotal to the discovery of neutrino flavour oscillations and are a unique tool to probe the reactions that keep the Sun shine. Although most of solar neutrino components have been directly measured, the neutrinos emitted by the keystone pp reaction, in which two protons fuse to make a deuteron, have so far eluded direct detection. The Borexino experiment, an ultra–pure liquid scintillator detector running at the Laboratori Nazionali del Gran Sasso in Italy, has now filled the gap, providing the first direct real time measurement of pp neutrinos and of the solar neutrino luminosity.

The Borexino experiment located in the Gran Sasso National Laboratory, is an organic liquid scintillator detector conceived for the real time spectroscopy of low energy solar neutrinos. The phase-I of the data taking campaign (2007 – 2010) has allowed the first independent measurements of 7Be and pep solar neutrino fluxes as well as the first measurement of anti-neutrinos from the Earth. After a purification of the scintillator, Borexino is now in phase-II since 2011. Thanks to the unprecedented background levels, we have performed the first flux measurement of neutrinos from the fundamental pp reaction which powers the Sun. We review this breakthrough result and other recent results, including the latest review of our terrestrial neutrino analysis. We also discuss the upcoming measurements on middle energy solar neutrino spectral components (pep, CNO) and the new project SOX devoted to the study of sterile neutrinos via the use of a neutrino source placed in close proximity of the detector’s active material.

An experiment to search for double beta processes in 106Cd by using cadmium tungstate crystal scintillator enriched in 106Cd (106CdWO4) in coincidence with the four crystals HPGe detector GeMulti is in progress at the STELLA facility of the Gran Sasso underground laboratory of INFN (Italy). The 106CdWO4 scintillator is viewed by a low-background photomultiplier tube through a lead tungstate crystal light-guide produced from deeply purified archaeological lead to suppress γ quanta from the photomultiplier tube. Here we report the first results of the experiment after 3233 hours of the data taking. A few new improved limits on double beta processes in 106Cd are obtained, in particular T1/22νεβ+ ≥ 8.4 × 1020 yr at 90% C.L.

Cerium, neodymium and gadolinium contain double beta active isotopes. The most interesting are 150Nd and 160Gd (promising for 0ν2β search), 136Ce (2β+ candidate with one of the highest Q2β). The main problem of compounds containing lanthanide elements is their high radioactive contamination by uranium, radium, actinium and thorium. The new generation 2β experiments require development of methods for a deep purification of lanthanides from the radioactive elements. A combination of physical and chemical methods was applied to purify cerium, neodymium and gadolinium. Liquid-liquid extraction technique was used to remove traces of Th and U from neodymium, gadolinium and for purification of cerium from Th, U, Ra and K. Co-precipitation and recrystallization methods were utilized for further reduction of the impurities. The radioactive contamination of the samples before and after the purification was tested by using ultra-low-background HPGe gamma spectrometry. As a result of the purification procedure the radioactive contamination of gadolinium oxide (a similar purification efficiency was reached also with cerium and neodymium oxides) was decreased from 0.12 Bq/kg to 0.007 Bq/kg in 228Th, from 0.04 Bq/kg to

Cadmium tungstate crystal scintillators enriched in 116Cd to 82% (116CdWO4, total mass of ≈1.2kg) are used to search for 2β decay of 116Cd deep underground at the Gran Sasso National Laboratory of the INFN (Italy). The radioactive contamination of the116CdWO4 crystals has been studied carefully to reconstruct the background of the detector. The measured half-life of 116Cd relatively to 2ν2β decay is T1/22ν2β = [2.8 ± 0.05(stat.) ± 0.4(syst.)] × 1019 yr, in agreement with the results of previous experiments. The obtained limit on the 0ν2β decay of 116Cd (considering the data of the last 8696 h run with an advanced background 0.12(2) counts/yr/kg/keV in the energy interval 2.7−2.9 MeV) is T1/2 ≥ 1.0 × 1023 yr at 90% C.L. The sensitivity of the experiment to the 0ν2β process is lim T1/2 = 3 × 1023 yr at 90% C.L. over 5 years of the measurements and it can be advanced (by further reduction of the background by a factor 3−30) to the level of lim T1/2 = (0.5-1.5) × 1024 yr for the same period of the data taking.

STELLA (SubTErranean Low Level Assay) is the ultra low background facility of the Gran Sasso National Laboratories (L.N.G.S.) in Italy. It is mainly devoted to material screening and rare events physics due to its very low radioactive background. Nevertheless, also environmental samples are measured within the collaboration with the ERMES (Environmental Radioactivity Monitoring for Earth Sciences) project. After a short description of the facility some on-going applications within the ERMES project will be briefly presented. The usefulness of doing environmental radioactivity measurements in a deep underground laboratory will be shortly discussed.

Monitoring of chemical and physical groundwater parameters has been carried out worldwide in seismogenic areas with the aim to test possible correlations between their spatial and temporal variations and strain processes. It is shown in this paper that uranium groundwater anomalies, which were observed in cataclastic rocks crossing the underground Gran Sasso National Laboratory (LNGS), can be used as a possible strain meter in domains where continental lithosphère is subducted. Moreover, whereas at the Gran Sasso National Laboratory only the natural radioactivity in the rock, the concrete, as well as the induced part coming from interaction of cosmic ray muons with the rock or the detector materials itself were considered as possible sources for the neutron flux background, the water-rock interaction and its spatial-temporal variation induced by the hydrological pattern of the Gran Sasso aquifer must be taken into account. Water must be considered not only as moderator in concrete, but also as additional source for neutron flux modulation due to its variable concentration and its radioactivity.

VIP-2 (VIolation of Pauli exclusion principle - 2) is an underground experiment sited in the underground “Laboratori Nazionali del Gran Sasso.” It aims to investigate possible violations of the Pauli Exclusion Principle (PEP) and, in this context, Quantum Gravity models implying violations of PEP. While an upper limit of PEP violation probability is recently published, the data requires further developments of accurate analysis techniques and methods. In this contribution, we present an overview of the methodologies proposed for current and planned analysis.