Identification and investigation of possible ultra-low Q value β decay candidates (original) (raw)
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Updated evaluation of potential ultra-low Q value βββ-decay candidates
2022
Ultra-low" Q value β decays are referred to as such due to their low decay energies of less than ∼1 keV. Such a low energy decay is possible when the parent nucleus decays into an excited state in the daughter, with an energy close to that of the Q value. These decays are of interest as potential new candidates for neutrino mass determination experiments and as a testing ground for studies of atomic interference effects in the nuclear decay process. In this paper, we provide an updated evaluation of atomic mass data and nuclear energy level data to identify potential ultra-low Q value β decay candidates. For many of these candidates, more precise and accurate atomic mass data is needed to determine if the Q value of the potential ultra-low decay branch is energetically allowed and in fact ultra-low. The precise atomic mass measurements can be achieved via Penning trap mass spectrometry.
Physical Review Letters, 2013
In anticipation of results from current and future double-beta decay studies, we report a measurement resulting in a 82 Se double-beta decay Q-value of 2997.9(3) keV, an order of magnitude more precise than the currently accepted value. We also present preliminary results of a calculation of the 82 Se neutrinoless double-beta decay nuclear matrix element that corrects in part for the small size of the shell model single-particle space. The results of this work are important for designing next generation double-beta decay experiments and for the theoretical interpretations of their observations.
Physical Review C, 2019
Background: Ultra-low Q-value β-decays are interesting processes to study with potential applications to nuclear β-decay theory and neutrino physics. While a number of potential ultra-low Q-value β-decay candidates exist, improved mass measurements are necessary to determine which of these are energetically allowed. Purpose: To perform precise atomic mass measurements of 89 Y and 139 La. Use these new measurements along with the precisely known atomic masses of 89 Sr and 139 Ba and nuclear energy level data for 89 Y and 139 La to determine if there could be an ultra-low Q-value decay branch in the β-decay of 89 Sr → 89 Y or 139 Ba → 139 La. Method: High-precision Penning trap mass spectrometry was used to determine the atomic mass of 89 Y and 139 La, from which β-decay Q-values for 89 Sr and 139 Ba were obtained. Results: The 89 Sr → 89 Y and 139 Ba → 139 La β-decay Q-values were measured to be QSr = 1502.20(0.35) keV and QBa = 2308.37(0.68) keV. These results were compared to energies of excited states in 89 Y at 1507.4(0.1) keV, and in 139 La at 2310(19) keV and 2313(1) keV to determine Q-values of-5.20(0.37) keV for the potential ultra-low β-decay branch of 89 Sr and-1.6(19.0) keV and-4.6(1.2) keV for those of 139 Ba. Conclusion: The potential ultra-low Q-value decay branch of 89 Sr to the 89 Y (3/2 − , 1507.4 keV) state is energetically forbidden and has been ruled out. The potential ultra-low Q-value decay branch of 139 Ba to the 2313 keV state in 139 La with unknown J π has also been ruled out at the 4σ level, while more precise energy level data is needed for the 139 La (1/2 + , 2310 keV) state to determine if an ultra-low Q-value β-decay branch to this state is energetically allowed.
Double-β-decay Q values of ^{130}Te, ^{128}Te, and ^{120}Te
Physical Review C, 2009
The double-beta decay Q values of 130 Te, 128 Te, and 120 Te have been determined from parentdaughter mass differences measured with the Canadian Penning Trap mass spectrometer. The 132 Xe-129 Xe mass difference, which is precisely known, was also determined to confirm the accuracy of these results. The 130 Te Q value was found to be 2527.01 ± 0.32 keV which is 3.3 keV lower than the 2003 Atomic Mass Evaluation recommended value, but in agreement with the most precise previous measurement. The uncertainty has been reduced by a factor of 6 and is now significantly smaller than the resolution achieved or foreseen in experimental searches for neutrinoless doublebeta decay. The 128 Te and 120 Te Q values were found to be 865.87 ± 1.31 keV and 1714.81 ± 1.25 keV, respectively. For 120 Te, this reduction in uncertainty of nearly a factor of 8 opens up the possibility of using this isotope for sensitive searches for neutrinoless double-electron capture and electron capture with β + emission.
Neutrinoless double beta decay and direct searches for neutrino mass
2004
* Full texts of the report of the working group. For the summary report of the APS Multidivisional Neutrino Study, 'The Neutrino Matrix', see physics/0411216 0νββ decay, independent of its rate, would show that neutrinos, unlike all the other constituents of matter, are their own antiparticles. There is no other realistic way to determine the nature-Dirac or Majorana, of massive neutrinos. This would be a discovery of major importance, with impact not only on this fundamental question, but also on the determination of the absolute neutrino mass scale, and on the pattern of neutrino masses, and possibly on the problem of CP violation in the lepton sector, associated with Majorana neutrinos. There is a consensus on this basic point which we translate into the recommendations how to proceed with experiments dedicated to the search of the 0νββ decay, and how to fund them. • To reach our conclusion, we have to consider past achievements, the size of previous experiments, and the existing proposals. There is a considerable community of physicists worldwide as well as in the US interested in pursuing the search for the 0νββ decay. Past experiments were of relatively modest size. Clearly, the scope of future experiments should be considerably larger, and will require advances in experimental techniques, larger collaborations and additional funding. In terms of m ββ , the effective neutrino Majorana mass that can be extracted from the observed 0νββ decay rate, there are three ranges of increasing sensitivity, related to known neutrino-mass scales of neutrino oscillations. • The ∼100-500 meV m ββ range corresponds to the quasi-degenerate spectrum of neutrino masses. The motivation for reaching this scale has been strengthened by the recent claim of an observation of 0νββ decay in 76 Ge; a claim that obviously requires further investigation. To reach this scale and perform reliable measurements, the size of the experiment should be approximately 200 kg of the decaying isotope, with a corresponding reduction of the background. This quasi-degenerate scale is achievable in the relatively near term, ∼ 3-5 years. Several groups with considerable US participation have well established plans to build ∼ 200-kg devices that could scale straightforwardly to 1 ton (Majorana using 76 Ge, Cuore using 130 Te, and EXO using 136 Xe). There are also other proposed experiments worldwide which offer to study a number of other isotopes and could reach similar sensitivity after further R&D. Several among them (e.g. Super-NEMO, MOON) have US participation. By making measurements in several nuclei the uncertainty arising from the nuclear matrix elements would be reduced. The development of different detection techniques, and measurements in several nuclei, is invaluable for establishing the existence (or lack thereof) of the 0νββ decay at this effective neutrino mass range. • The ∼20-55 meV range arises from the atmospheric neutrino oscillation results. Observation of m ββ at this mass scale would imply the inverted neutrino mass hierarchy or the normal-hierarchy ν mass spectrum very near the quasidegenerate region. If either this or the quasi-degenerate spectrum is established, it would be invaluable not only for the understanding of the origin of neutrino mass, but also as input to the overall neutrino physics program (long baseline oscillations, search for CP violations, search for neutrino mass in tritium beta decay and astrophysics/cosmology, etc.) To study the 20-50 meV mass range will require about 1 ton of the isotope mass, a challenge of its own. Given the importance, and the points discussed above, more than one experiment of that size is desirable. • The ∼2-5 meV range arises from the solar neutrino oscillation results and will almost certainly lead to the 0νββ decay, provided neutrinos are Majorana particles. To reach this goal will require ∼100 tons of the decaying isotope, and no current technique provides such a leap in sensitivity. • The qualitative physics results that arise from an observation of 0νββ decay are profound. Hence, the program described above is vital and fundamentally important even if the resulting m ββ would be rather uncertain in value. However, by making measurements in several nuclei the uncertainty arising from the nuclear matrix elements would be reduced. • Unlike double-beta decay, beta-decay endpoint measurements search for a kinematic effect due to neutrino mass and thus are "direct searches" for neutrino mass. This technique, which is essentially free of theoretical assumptions about neutrino properties, is not just complementary. In fact, both types of measurements will be required to fully untangle the nature of the neutrino mass. Excitingly, a very large new beta spectrometer is being built in Germany. This KATRIN experiment has a design sensitivity approaching 200 meV. If the neutrino masses are quasi-degenerate, as would be the case if the recent double-beta decay claim proves true, KATRIN will see the effect. In this case the 0νββ-decay experiments can provide, in principle, unique information about CP-violation in the lepton sector, associated with Majorana neutrinos. • Cosmology can also provide crucial information on the sum of the neutrino masses. This topic is summarized in a different section of the report, but it should be mentioned here that the next generation of measurements hope to be able to observe a sum of neutrino masses as small as 40 meV. We would like to emphasize the complementarity of the three approaches, 0νββ , β decay, and cosmology. Recommendations: We conclude that such a double-beta-decay program can be summarized as having three components and our recommendations can be summarized as follows:
The Decay Q Value of Neutrinoless Double Beta Decay
arXiv (Cornell University), 2022
An earlier publication "The implication of the atomic effects in neutrinoless double beta (0νββ) decay" written by Mei and Wei has motivated us to compare the decay Q value (Q ββ) derived from the decay of the parent nucleus to the daughter nucleus with the two ejected beta particles in the final state to the Q ββ directly derived from the decay of the initial neutral atom to the final state of double-ionized daughter ion with the two ejected beta particles in the final state. We show that the results are the same, which is the mass-energy difference (∆Mc 2) subtracted by the total difference of the atomic electron binding energy (∆E b) between the ground states of initial and final neutral atoms. We demonstrate that ∆Mc 2 is the sum of Q ββ and the atomic relaxation energy (∆E b) of the atomic structure after the decay. Depending on the atomic relaxation time, the release of the atomic binding energy may not come together with the energy deposition of the two ejected beta particles.
Double beta decays and neutrino masses
Journal of Physics: Conference Series, 2006
Neutrino-less double beta decays (0), which violate the lepton number conservation law by ÁL ¼ 2, are of great interest for studying the fundamental properties of neutrinos beyond the standard electroweak theory. High-sensitivity 0 studies with mass sensitivities of the solar and atmosphericmasses are crucial for studying the Majorana nature of 's, the mass spectrum, the absolute-mass scale, the Majorana CP phases and other fundamental properties of neutrinos and weak interactions. Actually, high-sensitivity experiments of 0 are the unique and practical method for studying all these fundamental properties of neutrinos in the foreseeable future. On the basis of the recent oscillation studies, the effective mass sensitivity required for observing the 0 rate is of the order of the atmospheric mass scale of m A $ 50 meV in the case of the inverted mass hierarchy and of the order of the solar mass scale of m S $ 8 meV in the case of the normal hierarchy. The present detectors with sensitivities of 150-300 meV are effective in the case of the quasi-degenerate mass spectrum. Future detectors with higher sensitivities of the orders of m Am S , using different nuclei and methods (calorimetric, spectroscopic), are indispensable for establishing 0. Theoretical and experimental studies for evaluating nuclear matrix elements M 0 within 20-30% are important for extracting the sensible mass from the 0 rate. Charge exchange reactions by means of nuclear, electron and probes provide useful data for M 0. International collaboration for experimental and theoretical works are encouraged to perform next-generation experiments. High-sensitivity detectors can be used for studying rare nuclear processes such as solar 's, dark matter, charge nonconservation, and nucleon decays. This report is a brief review of double beta decays and neutrinos with emphasis on highsensitivity 0 studies for the Majorana mass.
½+→½+Beta Decay with Neutrino Mass Effects in the Elementary Particle Treatment of Weak Interactions
Physical review, 1983
We compute the effect of a nonvanishing neutrino mass on the electron spectrum of tritium beta decay using the elementary particle treatment of weak interactions. Coulomb corrections are taken into account in this formalism, as are the effects of weak magnetism and nuclear recoil. The effect of a mixture of excited atomic final states is also discussed. These corrections combine to make small changes in the shape of the end point, which could be important in determinations of the neutrino mass. RADIOACTIVITY Calculation of neutrino mass and Coulomb effects on the spectrum of 3H P decay.
Cornell University - arXiv, 2022
Background: An ultra-low Q value β-decay can occur from a parent nuclide to an excited nuclear state in the daughter such that QUL 1 keV. These decay processes are of interest for nuclear β-decay theory and as potential candidates in neutrino mass determination experiments. To date, only one ultra-low Q value β-decay has been observed-that of 115 In with Q β = 147(10) eV. A number of other potential candidates exist, but improved mass measurements are necessary to determine if these decay channels are energetically allowed and, in fact, ultra-low. Purpose: To perform precise β-decay Q value measurements of 112,113 Ag and 115 Cd and to use them in combination with nuclear energy level data for the daughter isotopes 112,113 Cd and 115 In to determine if the potential ultra-low Q value β-decay branches of 112,113 Ag and 115 Cd are energetically allowed and 1 keV. Method: The Canadian Penning Trap at Argonne National Laboratory was used to measure the cyclotron frequency ratios of singly-charged 112,113 Ag and 115 Cd ions with respect to their daughters 112,113 Cd and 115 In. From these measurements, the ground-state to ground-state β-decay Q values were obtained. Results: The 112 Ag → 112 Cd, 113 Ag → 113 Cd, and 115 Cd → 115 In β-decay Q values were measured to be Q β (112 Ag) = 3990.16(22) keV, Q β (113 Ag) = 2085.7(4.6) keV, and Q β (115 Cd) = 1451.36(34) keV. These results were compared to energies of excited states in 112 Cd at 3997.75(14) keV, 113 Cd at 2015.6(2.5) and 2080(10) keV, and 115 In at 1448.787(9) keV, resulting in precise QUL values for the potential decay channels of-7.59(26) keV, 6(11) keV, and 2.57(34) keV, respectively. Conclusion: The potential ultra-low Q value decays of 112 Ag and 115 Cd have been ruled out. 113 Ag is still a possible candidate until a more precise measurement of the 2080(10) keV, 1/2 + state of 113 Cd is available. In the course of this work we have found the ground state mass of 113 Ag reported in the 2020 Atomic Mass Evaluation [Wang, et al., Chin. Phys. C 45, 030003 (2021)] to be lower than our measurement by 69(17) keV (a 4σ discrepancy).