Würzburg 2018 – scientific programme
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T: Fachverband Teilchenphysik
T 93: Experimentelle Methoden der Astroteilchenphysik V
T 93.6: Talk
Thursday, March 22, 2018, 17:45–18:00, Z6 - SR 2.013
Analytical Multivariate Fit in the Borexino Solar Neutrino Analysis — •Ömer Penek1, Simone Marcocci2, and Alina Vishneva3 for the Borexino collaboration — 1IKP-2, Forschungszentrum Jülich, 52428, Jülich, Germany — 2Gran Sasso Science Institute, 67100, L'Aquila, Italy — 3Joint Institute for Nuclear Research, 141980, Dubna, Russia
The Borexino detector, located at the Laboratori Nazionali del Gran Sasso in Italy, is a liquid scintillator detector with a primary goal to measure the solar neutrino fluxes. The spectral fit of the energy spectrum has been performed for the first time in the whole energy range from ~200 keV up to ~2 MeV. This approach made it possible to obtain the fluxes of 7Be, pp, and pep solar neutrinos simultaneously. To increase the sensitivity for pep neutrinos, the multivariate fit technique has been developed, which takes into account additional information of the radial and pulse shape distributions of events. To combine the respective likelihoods with the one of the spectral fit of energy spectra, a consistent theoretical description is needed. An additional challenge is represented by the convergence time of the fit itself. The talk shows the analytical multivariate fitting strategy used to obtain the new Borexino results for the 7Be, pp, and pep rates. We focus ourselves on the construction of the likelihood used in this analysis. This talk is presented in the name of the Borexino Collaboration.