Orateur
Dr
Ryan MacLellan
(University of Alabama)
Description
Double beta decay can be the dominant decay mode of some even-even nuclei for which the single beta decay is energetically forbidden or highly spin suppressed. This is a Standard Model second order weak process that produces, among other things, two neutrinos (2νββ). Should neutrinos be Majorana in nature, double beta decay could proceed without the emission neutrinos (0νββ). The observation of this process would require neutrinos to have Majorana masses, which can be related to the 0νββ decay rate, and lepton number conservation would be violated. I will review the status of current neutrinoless double beta decay searches.
EXO-200, in particular, is a 200 kg liquid Xe time projection chamber that has been installed underground at the WIPP facility outside Carlsbad, New Mexico. EXO-200 is a prototype for a future 1-10 ton Xe detector but, due to its ultra low background, it has already provided the first measurement of the 2νββ decay mode of Xe-136. While 2νββ decay has been observed by other experiments, this is the first observation using Xe-136 and, with a half-life of 2.11±0.04(stat.)±0.21(syst.)x10^21 yr, also the rarest decay directly observed. EXO-200 is currently collecting more data in an attempt to observe or to otherwise set new limits on the half-life of the 0νββ decay mode of Xe-136. On behalf of the EXO Collaboration, I will provide an update on the status of our search for double beta decay.
Auteur principal
Dr
Ryan MacLellan
(University of Alabama)
