The impact of Borexino on the solar and neutrino physics

The Borexino detector is characterized by a very low background level due to an unprecedented radio-purity, which allows to study the entire spectrum of solar neutrinos from very low energies (∼150 keV). The solar neutrino rates from pp, 7 Be, pep, 8 B (with a threshold down to 3 MeV) and a stringent limit of the CNO cycle rate have been already measured. In addition evidences of a null day/night asymmetry and of the solar neutrino flux seasonal variation have been reached

Precision Measurement of the (7)Be Solar Neutrino Interaction Rate in Borexino

A direct measurement of the 0.862 MeV 7Be solar neutrino interaction rate performed with the Borexino detector at the Laboratori Nazionali del Gran Sasso yields 46.0±1.5stat+1.6−1.5syst counts/day/(100 tons). Our result is the first direct measurement of a sub-MeV solar neutrino rate with an accuracy better than 5%. The hypothesis of no oscillation for 7Be solar neutrinos is rejected at 4.9σ C.L. Using the latest Standard Solar Model (SSM) flux predictions, the result leads directly to a precise determination of the survival probability for solar νe's in vacuum, and permits us to probe with unprecedented sensitivity the transition between the matter-enhanced and vacuum-dominated neutrino oscillation regimes characteristic of the MSW-LMA solution to the solar neutrino problem

alliance to penetrate mysteries of the earth

Muography and geoneutrinos, as applied to the investigation of Earth science topics, have developed during nearly the same timeframe. The idea of muography was first proposed in 1955 by E.P. George, a physicist who attempted to measure the areal density of the rock overburden of a tunnel underneath the Snowy Mountain Hydro-Electric Scheme in Australia. Thirteen years later, L. Alvarez first performed mugraphy in order to map out the internal structure of the Chephren's pyramid. With regard to geoneutrinos, George Gamow gave the first suggestion in a letter to F. Reines in 1953, two years prior to E.P. George's experiment. Enthusiastic about the idea in this letter, thirteen years later G. Eder discussed the potential of the "remarkable abundance of radioactive elements within the Earth". In the first decade of the 21st century, both the first muographic image of a volcano and the first measurement of geo-neutrinos respectively took place in 2006 and 2005. By encouraging the synergy of expertise in Earth science and particle physics, these new methods of studying previously invisible phenomenon within the Earth are continuing to improve as tools to solve Earth science challenges

Borexino : geo-neutrino measurement at Gran Sasso, Italy

Geo-neutrinos, electron anti-neutrinos produced in beta-decays of naturally occurring radioactive isotopes in the Earth, are a unique direct probe of our planet's interior. After a brief introduction of the geo-neutrinos' properties and of the main aims of their study, we discuss the features of a detector which has recently provided breakthrough achievements in the field, Borexino, a massive, calorimetric liquid scintillator detector installed at the underground Gran Sasso Laboratory. With its unprecedented radiopurity levels achieved in the core of the detection medium, it is the only experiment in operation able to study in real time solar neutrino interactions in the challenging sub-MeV energy region. Its superior technical properties allowed Borexino also to provide a clean detection of terrestrial neutrinos. Therefore, the description of the characteristics of the detected geo-neutrino signal and of the corresponding geological implications are the main core of the discussion contained in this work

Study of very low energy neutrinos from the Sun and from the Earth with the Borexino detector.

Borexino is a liquid scintillator unsegmented detector, running at the Gran Sasso underground Laboratories (LNGS). Thanks to its unprecedented low level of radioactive contamination, Borexino currently is the only experiment able to perform a real time measurement of solar neutrino interactions below few MeV. In solar neutrinos Borexino measured the neutrino flux from 7Be (862 keV) with total uncertainty smaller than 5%, the flux from 8B with a lower threshold down to 3 MeV, the day/night asymmetry of the 7Be neutrino flux with a total experimental uncertainty of 1%. These measurements introduce strong constraints also on the solar neutrino flux from the pp and CNO reactions. The impact of these Borexino results are extremely relevant both in solar physics, in connection with the understanding of Sun-like stars, and in neutrino physics. In particular, the precision measurement of the 7Be solar neutrino flux allows a real time investigation of neutrino oscillations below few MeV and provides a unique opportunity to probe and validate the currently favored neutrino oscillation paradigm in the so far untested /vacuum/regime. Furthermore, these results single out the Large Mixing Angle (LMA) region of the neutrino oscillation parameter space at the confidence level >8.5 sigma, without including the data from the KamLAND antineutrino reactor experiment in a combined fit, i.e. with no need to rely on CPT conservation in the neutrino sector. This outcome is especially interesting in view of the recent experimental hints of possible differences between the oscillation parameters of neutrino and antineutrino.In the geo-neutrinos, Borexino reached the first actual evidence of neutrinos from the Earth at 4.2 sigma C.L., connected with the radioactive decays in the Earth crust and mantle. Borexino is scheduled to continue data taking for the coming years and to further its investigation of solar neutrinos over the entire solar neutrino energy spectrum, pep and CNO (and perhaps pp) fluxes included. In the meantime the collected statistics of geoneutrinos is increasing to allow a better evaluation of the percentage of the terrestrial heat due to the radioactive decays