Status of the geochemical determination of the solar pp-neutrino flux by LOREX

Pavicevic, Milorad and Amthauer, Georg and Anicin, Ivan and Boev, Blazo and Bosch, Fritz and Bruchle, Willy and Djurcic, Z. and Faestermann, Thomas and Henning, Walter and Jelenkovic, Rade and Niedermann, Samuel and Pejovic, Vladan and Vermeesch, P. and Weiss, Achim (2012) Status of the geochemical determination of the solar pp-neutrino flux by LOREX. In: XXIV International Conference on Neutrino Physics and Astrophysics, 3 – 9 June 2012, Kyoto, Japan.

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LOREX, the acronym for LORandite EXperiment, is the only geochemical solar neutrino
experiment still actively pursued. It addresses the determination of the long-time
average of the solar neutrino flux with the thallium-bearing mineral lorandite,
TlAsS2, from the mine of Allchar, FYR Macedonia, via the neutrino-capture reaction
205Tl + ν(e) → 205Pb + e-. The final step of LOREX would be the extraction of
lorandite and the quantitative determination of the ratio of 205Pb / 205Tl atoms,
thus providing the product of solar neutrino flux and neutrino-capture cross section,
integrated over the age of lorandite of 4.31 ∙ 10^6 yr. Moreover, the detector
offers the lowest threshold among all the detectors of only 52 keV for solar ppneutrinos. This paper presents new data on accurate geological age of the minerals at
Allchar, as well as the recent results for erosion rates at two lorandite rich
locations. These are based on Accelerator Mass Spectrometry (AMS) determination of
10Be, 26Al and 53Mn in characteristic samples and on the independent geomorphological investigations. Reliable erosion rates are of paramount importance for
the proper determination of background of 205Pb induced by cosmic-ray muons. Provided
that these satisfactorily high values of erosion rates are corroborated by more
measurements of additional probes, the experiment is expected to reach an acceptable
signal-to-background ratio. Finally, it is discussed how to obtain the still unknown
capture probability of solar pp-neutrinos from 205Tl into 205Pb via the measurement
of the lifetime for the bound beta decay of the completely ionised 205Tl, as well as
how to count by Schottky mass spectrometry the extremely small number of 205Pb atoms
found within the few kilograms of the mineral, needed to attain the accuracy of the
final result of the order of some 30%. Both crucial measurements are planned to be
carried out at the GSI.

Item Type: Conference or Workshop Item (Paper)
Subjects: Natural sciences > Other natural sciences
Divisions: Faculty of Natural and Technical Sciences
Depositing User: Blazo Boev
Date Deposited: 28 May 2013 10:48
Last Modified: 17 Mar 2015 14:37

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