Towards the detection of low energy solar neutrinos in Borexino : data readout, data reconstruction and background identification [Doctoral thesis]

New challenging questions in astro-particle physics are opened with the discovery of neu- trino mass and mixing. Low energy solar neutrino spectroscopy plays now a fundamental role in understanding the new physics and the nuclear fusion processes in the sun. A large scale scintillation detector borexino at the Gran Sasso Laboratories (Italy) will soon pursue this goal in real time. In this work, a custom data acquisition system (electronics and software) has been developed together with the offline data processing algorithms. A water C\u2c7erenkov detector has been installed for cosmogenic background identification, including the tagging of 11C in the energy window of pep neutrinos. With a prototype detector, the in-situ 11C production rate was measured for the first time, resulting in 0.135 \ub1 0.024[stat] \ub1 0.014[syst]/d/ton. The detection of the weak spectral contribution of pep neutrinos in borexino was shown to be realistic and will determine uniquely the fundamental solar pp fusion rate