Mass and Double-Beta-Decay<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>Q</mml:mi></mml:math>Value of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mmultiscripts><mml:mi>Xe</mml:mi><mml:mprescripts /><mml:none /><mml:mn>136</mml:mn></mml:mmultiscripts></mml:math>

Redshaw, Matthew; Wingfield, E.; McDaniel, Joseph; Myers, E. G.

doi:10.1103/physrevlett.98.053003

Cited by 182 publications

(146 citation statements)

References 30 publications

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“…of the same order as for 0νββ. Determinations of Q-values 73 with precision spectroscopy 74 are also ongoing. This is particularly helpful for experiments in which the energy resolution is comparable to the current uncertainty of the Q-value.…”

Section: Standard Mechanismmentioning

confidence: 99%

Neutrino-Less Double Beta Decay and Particle Physics

Rodejohann

2011

Int. J. Mod. Phys. E

527

529

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We review the particle physics aspects of neutrino-less double beta decay. This process can be mediated by light massive Majorana neutrinos (standard interpretation) or by something else (non-standard interpretations). The physics potential of both interpretations is summarized and the consequences of future measurements or improved limits on the half-life of neutrino-less double beta decay are discussed. We try to cover all proposed alternative realizations of the decay, including light sterile neutrinos, supersymmetric or left-right symmetric theories, Majorons, and other exotic possibilities. Ways to distinguish the mechanisms from one another are discussed. Experimental and nuclear physics aspects are also briefly touched, alternative processes to double beta decay are discussed, and an extensive list of references is provided.

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Section: Standard Mechanismmentioning

confidence: 99%

Neutrino-Less Double Beta Decay and Particle Physics

Rodejohann

2011

Int. J. Mod. Phys. E

527

529

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“…Two drift regions are separated in the center by a cathode. The LXe is enriched to 80.6% in 136 Xe, the 0νββ candidate (Q = 2457.83 ± 0.37 keV [16]). The TPC provides X-Y-Z coordinate and energy measurements of ionization deposits in the LXe by simultaneously collecting the scintillation light and the charge.…”

Section: Exo-200 Detectormentioning

confidence: 99%

Search for Majorana neutrinos with the first two years of EXO-200 data

2014

Nature

382

318

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Many extensions of the Standard Model of particle physics suggest that neutrinos should be Majorana-type fermions, but this assumption is difficult to confirm. Observation of neutrinoless double-beta decay (0νββ), a spontaneous transition that may occur in several candidate nuclei, would verify the Majorana nature of the neutrino and constrain the absolute scale of the neutrino mass spectrum. Recent searches carried out with 76 Ge (GERDA experiment) and 136 Xe (KamLAND-Zen and EXO-200 experiments) have established the lifetime of this decay to be longer than 10 25 yr, corresponding to a limit on the neutrino mass of 0.2-0.4 eV. Here we report new results from EXO-200 based on 100 kg·yr of 136 Xe exposure, representing an almost fourfold increase from our earlier published datasets. We have improved the detector resolution at the 136 Xe double-betadecay Q-value to σ/E = 1.53% and revised the data analysis. The obtained half-life sensitivity is 1.9 · 10 25 yr, an improvement by a factor of 2.7 compared to previous EXO-200 results. We find no statistically significant evidence for 0νββ decay and set a half-life limit of 1.1 · 10 25 yr at 90% CL. The high sensitivity holds promise for further running of the EXO-200 detector and future 0νββ decay searches with nEXO. Majorana fermions, a class of neutral spin-1/2 particles described by 2-component spinors, have been an element of quantum field theory since its inception [1,2]. Electrons and other spin-1/2 elementary particles with distinct antiparticles, however, are described by 4-component Dirac spinors. Majorana quasiparticles may have been observed in condensed matter systems [3] where neutrality is achieved through the collective action of electrons and holes. Among the known elementary particles, only neutrinos are Majorana fermion candidates, owing to their intrinsic neutrality. Confirmation of this property would imply the non-conservation of lepton number, an additive quantum number that, unlike charge or color, is not related to any known gauge symmetry. As yet, lepton number has been empirically found to be conserved. Neutrinos are also remarkable for their small, yet finite, masses [4] that are generally difficult to explain, but arise naturally in many extensions [5,6] of the Standard Model of particle physics (SM). A generic consequence of many such extensions is that neutrinos should be of the Majorana variety.The most sensitive probe for Majorana neutrinos is a nuclear process known as neutrinoless double-beta decay (0νββ), whereby a nucleus decays by emitting two electrons and nothing else, while changing its charge by two units [7]. A related double-beta decay process, known as two-neutrino double-beta decay (2νββ), is allowed by the SM and has been observed in many nuclei, 136 Xe among them [8,9]. It provides, however, no direct information on the Majorana/Dirac question. The exotic 0νββ can be distinguished from the 2νββ by measuring the sum energy of the two electrons that is peaked at the Q-value for the former and is a continuum for the latter....

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“…The detector is a cylindrical homogeneous time projection chamber (TPC) [9]. It is filled with liquefied xenon ( [10]. Energy depositions in the TPC produce both ionization and scintillation signals.…”

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confidence: 99%