New results about the revolutionary bolometer assembly of BINGO

Abstract

Searching for neutrinoless double-beta decay (0$ν$2$β$) is one of the main experimental challenges of modern physics. One experimental technique is given by cryogenic detectors named bolometers that are really promising for this purpose. The current generation tonne-scale experiment CUORE using this technology is putting the best limit on $^{130}$Te 0$ν$2$β$ half-life with TeO$_2$ crystals but its sensitivity is limited by its background. Therefore, it will be followed by the next generation experiment CUPID (CUORE Upgrade with Particle IDentification) that will study $^{100}$Mo embedded inside Li$_2$MoO$_4$ crystals in order to reduce the $γ$ background. It will also read the scintillation light produced by Li$_2$MoO$_4$ by adding another Ge bolometer acting as a light detector next to the main absorber to reject the $α$ background. Thanks to that, CUPID will reach a sensitivity 2 orders of magnitude higher than CUORE. However, in the case where this is not enough to detect 0$ν$2$β$, BINGO (Bi-Isotope Next Generation 0$ν$2$β$ Observatory) is preparing the next-next generation of bolometric experiments. To improve the 0$ν$2$β$ discovery sensitivity, the goal is to reduce drastically the number of background events in the region of interest and to combine the use of the two previously cited isotopes: $^{130}$Te and $^{100}$Mo. To achieve this goal, BINGO is proposing to implement an active cryogenic veto to suppress the external $γ$ background, to use Neganov-Trofimov-Luke effect to increase light detector sensitivity and to use a revolutionary detector assembly to reduce the total surface radioactivity contribution. In this article, we will focus on the latter and present the latest results obtained with two 45$\times$45$\times$45 mm$^{3}$ Li$_2$MoO$_4$ crystals.