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Register a new userProspects of detection of relic antineutrinos by resonant absorption in electron capturing nuclei
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J.D. Vergados
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We consider the possibility of detecting relic anti-neutrinos by their resonant absorption in a nucleus, which can undergo electron capture. This possibility appears quite realistic in view of recent developments in Penning Trap Mass Spectrometry and cryogenic micro-calorimetry.
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Basic questions concerning phononless resonant capture of monoenergetic electron antineutrinos (Mossbauer 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. Mossbauer-antineutrino experiments could be used to gain new and deep insights into several basic problems in neutrino physics.
For the first time the antineutrino spectrum formed as a result of neutron and tritium decays during the epoch of primordial nucleosynthesis is calculated. This spectrum is a non-thermal increase in addition to the standard cosmic neutrino background (C$ u$B) whose thermal spectrum was formed before the beginning of primordial nucleosynthesis. For energy larger than $10^{-2},$eV the calculated non-thermal antineutrino flux exceeds the C$ u$B spectrum and there are no other comparable sources of antineutrino in this range. The observations of these antineutrinos will allow us to look directly at the very early Universe and non-equilibrium processes taken place before, during, and some time after primordial nucleosynthesis.
A search for resonant absorption of the solar axion by $^{83}rm{Kr}$ nuclei was performed using the proportional counter installed inside the low-background setup at the Baksan Neutrino Observatory. The obtained model independent upper limit on the combination of isoscalar and isovector axion-nucleon couplings $|g_3-g_0|leq 8.4times 10^{-7}$ allowed us to set the new upper limit on the hadronic axion mass of $m_{A}leq 65$ eV (95% C.L.) with the generally accepted values $S$=0.5 and $z$=0.56.
We discuss neutrino oscillations in an experiment with Mossbauer recoilless resonance absorbtion of tritium antineutrinos, proposed recently by Raghavan. We demonstrate that small energy uncertainty of antineutrinos which ensures a large resonance absorption cross section is in a conflict with the energy uncertainty which, according to the time-energy uncertainty relation, is necessary for neutrino oscillations to happen. The search for neutrino oscillations in the Mossbauer neutrino experiment would be an important test of the applicability of the time-energy uncertainty relation to a newly discovered interference phenomenon.
We propose a new class of bosonic dark matter (DM) detectors based on resonant absorption onto a gas of small polyatomic molecules. Bosonic DM acts on the molecules as a narrow-band perturbation, like an intense but weakly coupled laser. The excited molecules emit the absorbed energy into fluorescence photons that are picked up by sensitive photodetectors with low dark count rates. This setup is sensitive to any DM candidate that couples to electrons, photons, and nuclei, and may improve on current searches by several orders of magnitude in coupling for DM masses between 0.2 eV and 20 eV. This type of detector has excellent intrinsic energy resolution, along with several control variables---pressure, temperature, external electromagnetic fields, molecular species/isotopes---that allow for powerful background rejection methods as well as precision studies of a potential DM signal. The proposed experiment does not require usage of novel exotic materials or futuristic technologies, relying instead on the well-established field of molecular spectroscopy, and on recent advances in single-photon detection. Cooperative radiation effects, which arise due to the large spatial coherence of the nonrelativistic DM field in certain detector geometries, can tightly focus the DM-induced fluorescence photons in a direction that depends on the DMs velocity, possibly permitting a detailed reconstruction of the full 3D velocity distribution in our Galactic neighborhood, as well as further background rejection.
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