Next Generation Neutrinoless Double Beta Decay Experiments CUORE/CUORICINO (130Te) and Majorana (76Ge)

中微子是已知最轻的基本粒子。 它不带电荷，但有一个普朗克常数的半个单位的固有角动量（或自旋），就像它的表亲电子一样。它于1957年由Reines和科万发现，至今仍是基本动物园中最不为人所知的粒子之一。 根据传统的观点，在现代宇宙学中，宇宙中密集地分布着中微子。 因此，如果它们有足够大的质量，它们可能在宇宙的早期阶段甚至现在的演化中发挥重要作用。 大约90%的宇宙质量尚未被确定。 1998年，科学家宣布发现大气中宇宙射线μ子衰变产生的中微子在不同的族之间振荡。 这就要求它们确实有一定的质量，但这样的实验并不能得出多少。 当与中微子振荡结果相结合时，被称为双β衰变的假设罕见放射性衰变的速率可以产生非常有价值的信息。 如果一个原子核衰变时只发射两个电子，而不发射其他电子，那么就会产生这种现象的有趣版本。 这样的过程将违反一个重要的守恒定律，除非两个反中微子也与电子一起发射。 由于电子是轻子，而反中微子是反轻子，所以在有反中微子的衰变中，轻子的总数是守恒的。 要使衰变在没有反中微子的情况下发生，中微子一般必须具有质量，并且必须违反物理学中的一个重要对称性。 Majorana和CUORE实验是下一代无中微子双β衰变实验，对中微子质量的灵敏度有所提高，预计比迄今为止最好的实验好100倍。考虑到所有可用的数据，它们有很大的发现概率，能够提供关于中微子质量的重要信息，以及确定中微子是否有自己的反粒子。 CUORICINO是构建CUORE完整版的第一步。

The neutrino is the lightest known elementary particle. It has no electric charge but has an intrinsic angular-momentum(or spin) of one half unit of Planck's constant just like it's cousin the electron. Discovered in 1957 by Reines and Cowan, it remains one of the least understood particles in the elementary zoo. According to conventional wisdom, in modern cosmology the universe is densely populated with neutrinos. Accordingly,if they would have a large enough mass, they could have played an important role in the evolution of the universe in it's early stages and even at present. Approximately 90% of the mass of the universe has not been identified. In 1998 it was announced thatneutrinos resulting from the decay of cosmic-ray muons in the atmosphere were found to oscillate between different families. This would require that they do have some mass but such experiments do not yield how much. The rate of the hypothesized rare radioactive decay called double-beta decay can yield this very valuable information when combined with the neutrino oscillation results. The interesting version of this phenomenon would result if a nucleus would decay by emitting two electrons and nothing else. An important conservation law would be violated by such a process unless two anti-neutrinos were also emitted with the electrons. Since the electrons are leptons and the anti-neutrinos are anti-leptons the total number of leptons is conserved in the the decay with anti-neutrinos. For the decay to occur without anti-neutrinos, neutrinos in general must have mass and an important symmetry in physics must be violated. The Majorana and CUORE experiments, which are the subjects of this proposal, are next generation no-neutrino double-beta decay experiments with an improvement in the sensitivity to neutrino mass that is predicted to be about one hundred times better than the best experiments done to date.Considering all the data available, they have a significant probabilityfor discovery, for being able to provide important information on themass of neutrinos as well as to determine if neutrinos are there ownanti-particles. CUORICINO is a smaller first step towards building thefull version of CUORE.