"(Phys.org, July 19, 2012) Physicists Andrea Pocar and Krishna Kumar of the University of Massachusetts Amherst, part of an international research team, recently reported results of an experiment conducted at the Enriched Xenon Observatory (EXO), located in a salt mine one-half mile under Carlsbad, New Mexico, part of a decades-long search for evidence of the elusive neutrino-less double-beta decay of Xenon-136.
Pocar, Kumar and the team of 60 scientists using an instrument called the EXO-200 detector, succeeded in setting a new lower limit for the half-life of this ephemeral nuclear decay. Though no one has yet seen it, important progress was made.
Pocar explains, "This result is particularly interesting because it very nearly excludes a 10-year old claim for observing such a decay in germanium-76. One of the physics community's goals for all this time has been to test that claim. We now have a detector that is able to probe half-lives which are 10^15 times the age of the universe. This alone is a remarkable achievement."
If observed someday, the existence of neutrinoless double-beta decay would require a new theoretical explanation of particle physics, he adds. Many theorists believe that it should exist. "A number of factors make this seem possible. It could tell us something about the asymmetry between matter and anti-matter that we observe in the universe," Pocar notes. Latest findings are reported in the current issue of Physical Review Letters..."