17 research outputs found
M\"ossbauer Antineutrinos: Recoilless Resonant Emission and Absorption of Electron Antineutrinos
Basic questions concerning phononless resonant capture of monoenergetic
electron antineutrinos (M\"ossbauer antineutrinos) emitted in bound-state
beta-decay in the 3H - 3He system are discussed. It is shown that lattice
expansion and contraction after the transformation of the nucleus will
drastically reduce the probability of phononless transitions and that various
solid-state effects will cause large line broadening. As a possible
alternative, the rare-earth system 163Ho - 163Dy is favoured.
M\"ossbauer-antineutrino experiments could be used to gain new and deep
insights into several basic problems in neutrino physics
Probing the Earth's interior with a large-volume liquid scintillator detector
A future large-volume liquid scintillator detector would provide a
high-statistics measurement of terrestrial antineutrinos originating from
-decays of the uranium and thorium chains. In addition, the forward
displacement of the neutron in the detection reaction
provides directional information. We investigate the requirements on such
detectors to distinguish between certain geophysical models on the basis of the
angular dependence of the geoneutrino flux. Our analysis is based on a
Monte-Carlo simulation with different levels of light yield, considering both
unloaded and gadolinium-loaded scintillators. We find that a 50 kt detector
such as the proposed LENA (Low Energy Neutrino Astronomy) will detect
deviations from isotropy of the geoneutrino flux significantly. However, with
an unloaded scintillator the time needed for a useful discrimination between
different geophysical models is too large if one uses the directional
information alone. A Gd-loaded scintillator improves the situation
considerably, although a 50 kt detector would still need several decades to
distinguish between a geophysical reference model and one with a large neutrino
source in the Earth's core. However, a high-statistics measurement of the total
geoneutrino flux and its spectrum still provides an extremely useful glance at
the Earth's interior.Comment: 21 pages, 9 figures. Minor changes, version accepted for publication
in Astroparticle Physic
Search for modulations of the solar Be-7 flux in the next-generation neutrino observatory LENA
A next-generation liquid-scintillator detector will be able to perform
high-statistics measurements of the solar neutrino flux. In LENA, solar Be-7
neutrinos are expected to cause 1.7x10^4 electron recoil events per day in a
fiducial volume of 35 kilotons. Based on this signal, a search for periodic
modulations on sub-percent level can be conducted, surpassing the sensitivity
of current detectors by at least a factor of 20. The range of accessible
periods reaches from several minutes, corresponding to modulations induced by
helioseismic g-modes, to tens of years, allowing to study long-term changes in
solar fusion rates.Comment: 15 pages, 9 figure
Neutrinoless double-beta decay and seesaw mechanism
From the standard seesaw mechanism of neutrino mass generation, which is
based on the assumption that the lepton number is violated at a large
(~10exp(+15) GeV) scale, follows that the neutrinoless double-beta decay is
ruled by the Majorana neutrino mass mechanism. Within this notion, for the
inverted neutrino-mass hierarchy we derive allowed ranges of half-lives of the
neutrinoless double-beta decay for nuclei of experimental interest with
different sets of nuclear matrix elements. The present-day results of the
calculation of the neutrinoless double-beta decay nuclear matrix elements are
briefly discussed. We argue that if neutrinoless double-beta decay will be
observed in future experiments sensitive to the effective Majorana mass in the
inverted mass hierarchy region, a comparison of the derived ranges with
measured half-lives will allow us to probe the standard seesaw mechanism
assuming that future cosmological data will establish the sum of neutrino
masses to be about 0.2 eV.Comment: Some changes in sections I, II, IV, and V; two new figures;
additional reference
Energy-dependent light quenching in CaWO4 crystals at mK temperatures
Scintillating CaWO4 single crystals are a promising multi-element target for rare-event searches and are currently used in the direct dark matter experiment CRESST (Cryogenic Rare Event Search with Superconducting Thermometers). The relative light output of different particle interactions in CaWO4 is quantified by quenching factors (QFs). These are essential for an active background discrimination and the identification of a possible signal induced by weakly interacting massive particles (WIMPs). We present the first precise measurements of the QFs of O, Ca and W at mK temperatures by irradiating a cryogenic detector with a fast neutron beam. A clear energy dependence of the QF of O and, less pronounced, of Ca was observed for the first time. Furthermore, in CRESST neutron-calibration data a variation of the QFs among different CaWO4 single crystals was found. For typical CRESS