Astroparticle Colloquia

Searching for the Grail

by Prof. Juan Jose Gomez Cadenas (Donostia International Physics Center (DIPC))




More than eighty years ago Ettore Majorana, proposed that the neutrino could be its own antiparticle. As of today, Majorana neutrinos are still our best idea to explain the cosmic asymmetry between matter and antimatter.

Neutrinoless double beta decay (bbonu)  experiments are the only practical way to interrogate nature about the nature of neutrinos. But, due to the smallness of neutrino mass, the lifetime of the bb0nu process, if it exists is predicted to be very long. Thus experiments deploying several tons of rare isotopes such as Xe-136 are needed. On the other hand, the potencial background from natural radioactivity to a putative bb0nu decay is huge, so finding the bb0nu signal could be as difficult as identifying a single grain of sand in a large beach. We already know that lifetimes in the range of 10^27 years or even 10^28 years may need to be explored, which in turn implies designing setups which are virtually background free. Demonstrating that the neutrino is its own antiparticle becomes, thus, a true quest for the holy Grail, which only the bravest and purest of heart can attempt. 

In this talk I will describe the ways and weapons of some of the knights involved in the Quest, with some emphasis in the NEXT experiment, a relatively recent, but promising newcomer to the Round Table. 

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