Speaker
Description
CUPID-Mo, located at the Laboratoire Souterrain de Modane, in France was a demonstrator for CUPID, a next generation search for $0 \nu \beta \beta$ in $^{100}$Mo. It consisted of an array of 20 Li$_2$MoO$_4$ bolometers and 20 Ge light detectors for particle ID. It has demonstrated excellent crystal radio-purity ($^{238}$U/$ ^{232}$Th chains $0.3 - 1$ $\mathrm{\mu Bq/kg}$ for relevant isotopes), $\alpha$, $\beta/\gamma$ particle discrimination ($>99.9\%$), and energy resolution ($\sim 7 \ \mathrm{keV}$ FWHM at $2615$ $\mathrm{keV}$). This performance allowed CUPID-Mo to place the leading limit on the half life of $0 \nu \beta \beta$ in $^{100}$Mo of $T_{1/2}^{0 \nu}>1.5 \cdot 10^{24}$\,yr despite a very modest $2.16$ kg-yr exposure.
In this work we present the results from the search for double beta decays of $^{100}$Mo to excited states of $^{100}$Ru. Precision measurement of the $2\nu\beta\beta$ decay can help constrain nuclear models which are needed to interpret $0\nu\beta\beta$ results as a limit on the neutrino mass.
In these decays, the electrons are accompanied by one or more de-excitation gamma quanta. Multi-site events provide a very clear experimental spectrum technique to search for these decays and separate them from possible background sources.
Finally, we demonstrate how the analysis techniques we have developed could be employed by the next generation experiment CUPID to reach an unprecedented sensitivity to decays to excited states and other rare processes.
