Measurement of the2νββdecay half-life ofNd150and a search for

R. Arnold¹,

C. Augier²,

J. D. Baker³

et al.

Abstract

We present results from a search for neutrinoless double-β (0νββ) decay using 36.6 g of the isotope 150 Nd with data corresponding to a live time of 5.25 y recorded with the NEMO-3 detector. We construct a complete background model for this isotope, including a measurement of the twoneutrino double-β decay half-life of T 2ν 1/2 = [9.34 ± 0.22 (stat.)18 y for the ground state transition, which represents the most precise result to date for this isotope. We perform a multivariate analysis to search for 0νββ decays in order to improve the sensitivity and, in the case of observation, disentangle the possible underlying decay mechanisms. As no evidence for 0νββ decay is observed, we derive lower limits on half-lives for several mechanisms involving physics beyond the Standard Model. The observed lower limit, assuming light Majorana neutrino exchange mediates the decay, is T 0ν 1/2 > 2.0 ×10 22 y at the 90% C.L., corresponding to an upper limit on the effective neutrino mass of mν < 1.6 -5.3 eV.

Leptonic scalars at the LHC

“…This topology is the same as the one for the emission of a Majoron from neutrinoless double beta (0νββ) decay process [9,10]. For Majoron masses smaller than O(MeV) -the typical Q-value for relevant nuclei, strong JHEP07(2020)142 limits on the coupling λ ee 10 −4 [5] have been set by 0νββ experiments like NEMO-3 [11][12][13][14][15][16], KamLAND-Zen [17], EXO-200 [18] and GERDA [19]. In this paper, we show that high-energy colliders like LHC provide a novel complementary probe of the couplings λ αβ through the VBF process (1.2) that extends the experimental reach to relatively higher φ masses.…”

Systematic classification of two-loop d = 4 Dirac neutrino mass models and the Diracness-dark matter stability connection

“…, (4b) with the shorthand k ≡ (16π 2 ) d 4 k/(2π) 4 . Both integrals can be written in terms of simple one-loop and two-loop integrals, for which analytical expressions can be found.…”

Searching for New Physics in Two-Neutrino Double Beta Decay

“…On the other hand, the NEMO-3 experiment with the technology to track individual electrons can measure the individual electron energy spectra and the opening angle between the two electrons. This has yielded detailed measurements of the 2νββ decay spectra of 96 Zr [6], 150 Nd [7], 48 Ca [8], 82 Se [9], and especially 100 Mo [10], the latter with a very high statistics containing ≈5 × 10 5 2νββ decay events. Such measurements are important for the interpretation of 0νββ decay searches, as it can shed light on the value of the effective axial coupling g A [11].…”