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Free keywords:
Beta decay, Nuclear astrophysics, Solar neutrinos, 190 ≤ A ≤ 219
MPINP:
Präzisionsexperimente - Abteilung Blaum
Abstract:
Stable 205Tl ions have the lowest known energy threshold for capturing electron neutrinos (ve) of Eve≥50.6 keV. The Lorandite Experiment (LOREX), proposed in the 1980s, aims at obtaining the longtime averaged solar neutrino flux by utilizing natural deposits of Tl-bearing lorandite ores. To determine the ve capture cross section, it is required to know the strength of the weak transition connecting the ground state of 205Tl and the 2.3 keV first excited state in 205Pb. The only way to experimentally address this transition is to measure the bound-state beta decay (ßb) of fully ionized 205Tl81+ ions. After three decades of meticulous preparation, the half-life of the ßb decay of 205Tl81+ has been measured to be 291−27+33 days using the Experimental Storage Ring (ESR) at GSI, Darmstadt. The longer measured half-life compared to theoretical estimates reduces the expected signal-to-noise ratio in the LOREX, thus challenging its feasibility.
