Description
Borexino, located at the Laboratori Nazionali del Gran Sasso in Italy, is a liquid scintillator detector that measures solar neutrinos via their forward elastic scattering off electrons . Thanks to the unprecedented radiopurity achieved by the Borexino detector, the real time spectroscopy of solar neutrinos from both the pp chain and CNO fusion cycle of the Sun has been performed. In addition, it is now possible to identify the solar neutrino signal in a liquid scintillator using the few Cherenkov photons emitted at early times, in the direction of scattered electrons with a lower energy threshold of 0.16 MeV. The directional solar neutrino signal is discriminated from the isotropic background events by correlating the well known position of the Sun and the direction of the first two time-of-flight subtracted photomultipler (PMT) hits of each event, with respect to the reconstructed vertex. This technique is called Correlated and Integrated Directionality (CID). This angular distribution in data is fitted with the signal and background distributions from Borexino Monte Carlo simulation with the effective refractive index for Cherenkov photons tuned using various gamma sources from the Borexino Calibration campaign. This poster will describe the analysis strategy and methods used to disentangle the sub-MeV solar neutrino signal in data to extract the Be7 interaction rate in the Borexino Phase-1 period (May 2007-May 2010).
| Collaboration | Borexino collaboration |
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