Dortmund 2021 – wissenschaftliches Programm
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T: Fachverband Teilchenphysik
T 94: Neutrino physics without accelerators VII
T 94.2: Vortrag
Donnerstag, 18. März 2021, 16:20–16:35, Ts
210Bi upper limit for the direct evidence of CNO solar neutrinos with Borexino — •Sindhujha Kumaran1,2, Alexandre Göttel1,2, Livia Ludhova1,2, Luca Pelicci1,2, Ömer Penek1,2, Giulio Settanta1, and Apeksha Singhal1,2 for the Borexino collaboration — 1Forschungszentrum Jülich - Institute for Nuclear Physics, IKP-2, Jülich, Germany — 2RWTH Aachen University - Physics Institute III B, Aachen, Germany
Borexino is a liquid scintillator detector located at the Laboratori Nazionale del Gran Sasso, Italy with the main goal to measure solar neutrinos. The experiment recently provided the first direct experimental evidence of CNO-cycle neutrinos in the Sun. The intrinsic 210Bi is an important background for this analysis due to its similar spectral shape to that of CNO neutrinos. 210Bi β− decays to 210Po, which then α decays to stable 206Pb. Ideally, 210Bi should be in secular equilibrium with 210Po and 210Po can be distinguished through an event-by-event basis via pulse shape discrimination techniques. Until mid-2016, additional 210Po was brought from peripheral sources to the detector’s fiducial volume via the convective motions of the scintillator, triggered by seasonal temperature changes. However, the thermal insulation performed in 2015-16 has thermally stabilized the detector, achieving low levels of convection in the innermost region and making it possible to measure 210Bi via 210Po. This talk will present the strategy and the methods used to extract the 210Bi upper limit in Phase-III (Jul 2016- Feb 2020) of the experiment via the analysis of 210Po in the cleanest region of the detector called the Low Polonium Field.