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Title: Molecular effects in investigations of tritium molecule {beta} decay endpoint experiments

Abstract

The final state distribution of the first six electronic states of {sup 3}HeT{sup +},{sup 3}HeD{sup +} and {sup 3}HeH{sup +} resulting from the {beta} decay of T{sub 2}, DT, and HT are calculated, to satisfy the higher-resolution requirements and increased sensitivity of the future tritium neutrino mass experiments. The sensitivity of the initial temperature, ortho-para ratio, and isotopic composition of the source is considered. Estimates of the error in the value of the neutrino mass deduced from fitting, due to uncertainties in the temperature, the ortho-para ratio of T{sub 2}, and the percentage of DT molecules in the source are presented.

Authors:
; ; ;  [1];  [2];  [3]
  1. Department of Physics and Astronomy, University College London, Gower Street, WC1E 6BT London (United Kingdom)
  2. (Germany)
  3. (Sweden)
Publication Date:
OSTI Identifier:
20771296
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. C, Nuclear Physics; Journal Volume: 73; Journal Issue: 2; Other Information: DOI: 10.1103/PhysRevC.73.025502; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; BETA DECAY; DEUTERIUM; DISTRIBUTION; ELECTRONIC STRUCTURE; HELIUM 3; ISOTOPE RATIO; MOLECULAR IONS; MOLECULES; NEUTRINOS; RESOLUTION; SENSITIVITY; TRITIUM

Citation Formats

Doss, Natasha, Tennyson, Jonathan, Saenz, Alejandro, Jonsell, Svante, AG Moderne Optik, Institut fuer Physik, Humboldt-Universitaet zu Berlin, Hausvogteiplatz 5-7, D-10 117 Berlin, and Department of Physics, Umeaa University, SE-90187 Umeaa. Molecular effects in investigations of tritium molecule {beta} decay endpoint experiments. United States: N. p., 2006. Web. doi:10.1103/PhysRevC.73.025502.
Doss, Natasha, Tennyson, Jonathan, Saenz, Alejandro, Jonsell, Svante, AG Moderne Optik, Institut fuer Physik, Humboldt-Universitaet zu Berlin, Hausvogteiplatz 5-7, D-10 117 Berlin, & Department of Physics, Umeaa University, SE-90187 Umeaa. Molecular effects in investigations of tritium molecule {beta} decay endpoint experiments. United States. doi:10.1103/PhysRevC.73.025502.
Doss, Natasha, Tennyson, Jonathan, Saenz, Alejandro, Jonsell, Svante, AG Moderne Optik, Institut fuer Physik, Humboldt-Universitaet zu Berlin, Hausvogteiplatz 5-7, D-10 117 Berlin, and Department of Physics, Umeaa University, SE-90187 Umeaa. Wed . "Molecular effects in investigations of tritium molecule {beta} decay endpoint experiments". United States. doi:10.1103/PhysRevC.73.025502.
@article{osti_20771296,
title = {Molecular effects in investigations of tritium molecule {beta} decay endpoint experiments},
author = {Doss, Natasha and Tennyson, Jonathan and Saenz, Alejandro and Jonsell, Svante and AG Moderne Optik, Institut fuer Physik, Humboldt-Universitaet zu Berlin, Hausvogteiplatz 5-7, D-10 117 Berlin and Department of Physics, Umeaa University, SE-90187 Umeaa},
abstractNote = {The final state distribution of the first six electronic states of {sup 3}HeT{sup +},{sup 3}HeD{sup +} and {sup 3}HeH{sup +} resulting from the {beta} decay of T{sub 2}, DT, and HT are calculated, to satisfy the higher-resolution requirements and increased sensitivity of the future tritium neutrino mass experiments. The sensitivity of the initial temperature, ortho-para ratio, and isotopic composition of the source is considered. Estimates of the error in the value of the neutrino mass deduced from fitting, due to uncertainties in the temperature, the ortho-para ratio of T{sub 2}, and the percentage of DT molecules in the source are presented.},
doi = {10.1103/PhysRevC.73.025502},
journal = {Physical Review. C, Nuclear Physics},
number = 2,
volume = 73,
place = {United States},
year = {Wed Feb 15 00:00:00 EST 2006},
month = {Wed Feb 15 00:00:00 EST 2006}
}
  • The energies and wave functions for the lowest six electronic /sup 1/..sigma../sup +/ states of the HeT/sup +/ molecule have been obtained for 0.6< or =R< or =4.0 bohr. The overlap integrals between these wave functions and those for the ground state of the T/sub 2/ molecule have been calculated. The results show that the probability of T/sub 2/ decaying into HeT/sup +/ discrete electronic states amounts to 0.852, with the lowest six states accounting for 0.8422.
  • We present the relativistic calculation of the {beta}-decay of tritium in a hadron model. The elementary particle treatment (EPT) of the transition {sup 3}H {yields}{sup 3}He +e{sup -}+{nu}{sub e} is performed in analogy with the description of the {beta}-decay of neutron. The effects of higher order terms of hadron current and nuclear recoil are taken into account in this formalism. The relativistic Kurie function is derived and presented in a simple form suitable for the determination of neutrino masses from the shape of the endpoint spectrum. A connection with the commonly used Kurie function is established.
  • Probabilities have been computed for transitions induced by a ..beta..-decay process from the ground rovibronic state of the T/sub 2/ molecule to various bound rovibrational and scattering states connected with the first six /sup 1/..sigma../sup +/ electronic states of the /sup 3/HeT/sup +/ ion. Analogous calculations were performed for the TH source but only the ground electronic state of the daughter system was considered. For transitions from the T/sub 2/ source to the ground electronic state of the daughter ion a probability equal to 0.4083 is associated with bound rovibrational states while 0.1659 is associated with scattering states. The samemore » values for the TH source are 0.5572 and 0.0136, respectively. It is shown that the use of a TH source is not advantageous in a neutrino-mass experiment. Numerical accuracies of our calculations have been checked by making extensive use of sum rules. The total error in the final result is discussed.« less
  • The theoretical aspects of the ..beta..-decay process in T/sub 2/ as they relate to neutrino-mass experiments are discussed. We present new results from stabilization method calculations for the resonance states of the daughter HeT/sup +/ ion. The probabilities for this system to be found in various final shake-off states after the T/sub 2/ decay have been calculated. The ..beta..-decay energy spectra are generated using probability distributions of various accuracies. It is shown that, if the actual neutrino mass were 30 eV, one would obtain masses of 6 and 25 eV using spectra of the bare tritium nucleus and the tritiummore » atom, respectively, for analyzing the data. If the nuclear motion effects were neglected, the obtained mass would be 30 eV but the end-point energy would be shifted by 1.5 eV. For a 30-eV mass the accuracy of our calculations is much better than necessary: Substituting our data by those obtained with a very poor basis set changed the neutrino mass only by about 1 eV. For a 1-eV mass, however, the less accurate calculation would introduce a substantial error. In particular, including the effects of nuclear motion is important to correctly determine a 1-eV mass. The accuracy with which resonance states of the daughter ion are determined has practically no influence on the final result. We argue that most solid-state effects will lead to corrections small compared to the expected experimental errors.« less
  • We have computed the excitation probabilities of the T/sub 2/ molecules in the crystal surrounding the ..beta..-decaying tritium. The influence of this effect on the neutrino mass determination has been studied. For a neutrino mass of the order of a few eV the effect has been shown to be very important. Its importance decreases, however, with increasing neutrino mass. In addition we consider the influence of the high-energy portion (E>164 eV) of the probability distribution on the neutrino mass.