nucl-th digest · Dec 5, 2016

μ^{-}

e^{+}

Conversion from Short-Range Operators

We present a detailed discussion of the lepton flavour and number violating conversion of bound muons into positrons. This process is a viable alternative to neutrinoless double beta decay and, given that experiments on ordinary

μ^{-}

e^{-}

conversion are expected to improve their sensitivities by several orders of magnitude in the coming years, we can also assume the limit on

μ^{-}

e^{+}

conversion to improve by roughly the same factor. We discuss how new physics at a high scale can lead to short-range contributions to this conversion process and we present one explicit case in great detail (the single one for which the corresponding nuclear matrix element is presently known). The main goal of our discussion is to make the respective computation accessible to the particle physics community, so that promising models can be investigated while the nuclear physics community can simultaneously advance the computation of nuclear matrix elements. Given the progress to be expected on the experimental side, it may even be possible that lepton number violation in the

e μ

-sector is discovered by

μ^{-}

e^{+}

conversion before neutrinoless double beta decay can show its existence in the

ee

-sector.

Comments:: 34 pages, 9 figures
Subjects:: High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:: 1612.00452 [pdf]

PRD(2017)·21 citations

[Submitted on 2 Dec 2016] (cross-list from nucl-ex)

Reactors as a source of antineutrinos: the effect of fuel loading and burnup for mixed oxide fuels

Adam Bernstein🇺🇸 · Nathaniel Bowden🇺🇸 · Anna Erickson🇺🇸

In a conventional light water reactor loaded with a range of uranium and plutonium-based fuel mixtures, the variation in antineutrino production over the cycle reflects both the initial core fissile inventory and its evolution. Under the assumption of constant thermal power, we calculate the rate at which antineutrinos are emitted from variously fueled cores, and the evolution of that rate as measured by a representative ton-scale antineutrino detector. We find that antineutrino flux decreases with burnup for Low Enriched Uranium cores, increases for full mixed-oxide (MOX) cores, and does not appreciably change for cores with a MOX fraction of approximately 75%. Accounting for uncertainties in the fission yields, in the emitted antineutrino spectra, and the detector response function, we show that the difference in core-wide MOX fractions at least as small as 8% can be distinguished using a hypothesis test. The test compares the evolution of the antineutrino rate relative to an initial value over part or all of the cycle. The use of relative rates reduces the sensitivity of the test to an independent thermal power measurement, making the result more robust against possible countermeasures. This rate-only approach also offers the potential advantage of reducing the cost and complexity of the antineutrino detectors used to verify the diversion, compared to methods that depend on the use of the antineutrino spectrum. A possible application is the verification of the disposition of surplus plutonium in nuclear reactors.

Comments:: 9 pages, 9 figures, 4 tables
Subjects:: Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th); Instrumentation and Detectors (physics.ins-det)
arXiv:: 1612.00540 [pdf]

Phys.Rev.Applied(2018)·19 citations

Monday·December 5, 2016

$μ^{-}$ - $e^{+}$ Conversion from Short-Range Operators

Reactors as a source of antineutrinos: the effect of fuel loading and burnup for mixed oxide fuels

Affiliations

μ−- e+ Conversion from Short-Range Operators

Reactors as a source of antineutrinos: the effect of fuel loading and burnup for mixed oxide fuels

Affiliations

$μ^{-}$ - $e^{+}$ Conversion from Short-Range Operators