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

中微子是已知的最轻的基本粒子。它不带电荷，但本征角动量(或自旋)是普朗克常数的一半单位，就像它的表亲电子一样。它由Reines和Cowan于1957年发现，至今仍是基本动物园中最不为人所知的粒子之一。根据传统观点，在现代宇宙学中，宇宙中密集分布着中微子。因此，如果它们有足够大的质量，它们可能会在宇宙的早期阶段甚至现在的演化中发挥重要作用。宇宙中约90%的质量尚未确定。1998年，人们宣布，发现大气中宇宙射线介子衰变产生的中微子在不同家族之间振荡。这将要求它们确实有一定的质量，但这样的实验不会产生多少质量。假设的稀有放射性衰变的速率称为双β衰变，当与中微子振荡结果相结合时，可以产生这一非常有价值的信息。如果原子核只发射两个电子，而不发射其他电子，就会产生这种现象的有趣版本。除非电子同时发射出两个反中微子，否则这样的过程会违反一个重要的守恒定律。由于电子是轻子，反中微子是反轻子，所以轻子总数在与反中微子的衰变中是守恒的。要想在没有反中微子的情况下发生衰变，中微子通常必须有质量，而且物理学中的一个重要对称性必须被破坏。作为这项提议的主题，Majorana和CuORE实验是新一代非中微子双β衰变实验，其对中微子质量的敏感度预计将比迄今最好的实验提高约100倍。考虑到所有现有数据，它们有很大的发现可能性，因为它们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具有反粒子。Cuoricino是构建完整版CUORE的较小的第一步。

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.