The double beta decay spectrum of¹⁰⁰Mo as measured with a TPC

Abstract

A time projection chamber with 8.3 grams of enriched 100MoO3 as the central electrode has been operating approximately five months in an underground laboratory. A preliminary analysis of the two-electron sum energy spectrum, the spectrum of those same electrons taken singly, and the opening angle distribution yields a half life of 1.16-0.08+0.34*1019 y at the 68% confidence level for two-neutrino double beta decay of 100Mo.

Two-neutrino double- β decay of 94 ⩽ A ⩽ 110 nuclei for the 0+ → 0+ transition

“…On the other hand, the M 2ν predicted by Engel et al [52] and Civitarese et al [67] for g A =1.0 are in agreement with the results of LBL [60], LBL collaboration [62], UC Irvine [63] and ITEP+INFN [65] due to experimental error bars. The values of M 2ν predicted in SU(4) στ [56] and SU3(SPH) [66] are nearly identical and close to the experimental result given by Vasilev et al [57] and ITEP+INFN [65] [58], ELEGANTS V [59], LBL [60], NEMO [61], LBL collaboration [62] and ITEP+INFN [65] for g A =1. 25.…”

“…The predicted T 2ν 1/2 in QRPA by Staudt et al [45] and in OEM by Hirsch et al [46] are larger than our predicted value for g A =1.0 by approximately a factor of 2 and 4 respectively. The 2ν ββ decay of 100 Mo for 0 + →0 + transition have been investigated by many experimental groups [18,51,[57][58][59][60][61][62][63][64][65] as well as theoreticians by employing different theoretical frameworks [29,30,[45][46][47]52,53,56,[66][67][68]. In comparison to the experimental M 2ν , the theoretically calculated value given by Stoica using SRPA(WS) [53] is too small.…”

Measurement of the2νββdecay half-life ofNd150and a search forArnold1, Augier2, Baker3 et al. 2016Phys. Rev. D

“…A group at the University of California, Irvine conducted the first measurement, using a time projection chamber (TPC) located approximately 72 m underground at the Hoover Dam [8]. With 15.5 g of Nd 2 O 3 enriched to 91% of the isotope 150 Nd and a live time of 262 d, the half-life was measured to be T 18 y [12].…”

Charged majoron emission in neutrinoless double beta decay

“…Thus, to account for an anomalous excess of ββ events for which some experimental groups had preliminary evidence [9], Burgess and Cline recently advocated a new class of "charged majoron" models [10,11] so-named because their majoron carries the U(1) charge of lepton number, presumed to be unbroken. Refs.…”

“…In computing the relevant nuclear matrix elements, we have not considered the effects of finite nucleon size or short-range two-nucleon correlations, which would tend to reduce the calculated matrix elements [12]. On the other hand, the arguments used to simplify the nuclear transition operator from (8) to (9) are not rigorous, and it is also possible that future variants of the CMM considered here might evade the suppression of the rate by the mixing angle θ. Thus, while we believe that ours is the most quantitative analysis of the CMM to date, if the experimental situation should give serious indications of anomalous ββ decay events in the future, it would become appropriate to undertake a yet more careful evaluation of the model's predictions.…”