Double Beta Decay Experiments at Canfranc Underground Laboratory

TL;DR

This paper reviews the history and progress of double beta decay experiments at the Canfranc Underground Laboratory, highlighting technological innovations and recent experimental limits on neutrinoless double beta decay half-lives.

Contribution

It provides a comprehensive overview of experimental approaches and results in double beta decay research at LSC, including new detector technologies and future project plans.

Findings

IGEX set a half-life limit of >1.57×10^{25} years for ^76Ge

NEXT-100 expects a limit of >1.0×10^{26} years for ^136Xe

CROSS aims for a limit of >2.8×10^{25} years for ^100Mo

Abstract

The first activities of the Canfranc Underground Laboratory ("Laboratorio Subterr\'aneo de Canfranc", LSC) started in the mid-eighties in a railway tunnel located under the Spanish Pyrenees; since then, it has become an international multidisciplinary facility equipped with different services for underground science. The research activity at LSC is about Astroparticle Physics, dark matter searches and neutrino Physics; but also activities in Nuclear Astrophysics, Geophysics, and Biology are carried out. The investigation of the neutrinoless double beta decay has been one of the main research lines of LSC since the beginning. Many unknowns remain in the characterization of the basic neutrino properties and the study of this rare decay process requiring Physics beyond the Standard Model of Particle Physics can shed light on the lepton number conservation, the nature of the neutrinos as Dirac or Majorana particles and the absolute scale and ordering of the masses of the three generations. Here, the double beta decay searches performed at LSC for different emitters and following very different experimental approaches will be reviewed: from the very first experiments in the laboratory including the successful IGEX for $^{76}$Ge, which released very stringent limits to the effective neutrino mass at the time, to the present NEXT experiment for $^{136}$Xe and future project CROSS ("Cryogenic Rare-event Observatory with Surface Sensitivity") for $^{130}$Te and $^{100}$Mo, both implementing innovative detector technologies to discriminate backgrounds. For the neutrinoless double beta decay channel and at 90% C.L., IGEX derived a limit to the half-life of $^{76}$Ge of $T_{1/2}^{0\nu} > 1.57 \times 10^{25}$ y while the corresponding expected limits are $T_{1/2}^{0\nu} > 1.0\times 10^{26}$ y for $^{136}$Xe from NEXT-100 (for an exposure of 500 kg.y) and $T_{1/2}^{0\nu} > 2.8 \times 10^{25}$ y for $^{100}$Mo from CROSS (for 5 y and 4.7 kg of isotope). Activities related to double beta decays searches carried out in other underground laboratories have also been developed at LSC and will be presented too, like the operation of the BiPo-3 detector for radiopurity measurements of thin sheets with very high sensitivity. For each one of these experiments, the concept, the experimental set-ups and relevant results will be discussed.