UK Neutrino Network

1930年，奥地利物理学家沃尔夫冈·保利提出了一种名为中微子的粒子的存在，作为一种名为贝塔衰变的放射性活动中能量缺失的“绝药”。他推断，一些能量一定被衰变过程中释放出的新粒子--中微子带走了。从那时起，经过几十年艰苦的实验和理论工作，中微子已经成为公认的基本粒子和力的量子描述的重要组成部分，即粒子物理标准模型。这是一个非常成功的理论，在这个理论中，物质的基本构件被分为三代两种粒子-夸克和轻子。它还包括三种基本的自然力，但不包括重力。轻子包括带电的电子、介子和介子，以及三个电中性粒子--电子中微子、介子中微子和陶子中微子。然而，与夸克和带电轻子的情况不同，标准模型预测中微子没有质量！对于物质粒子来说，这似乎很奇怪，但标准模型预测，中微子总是左旋--就像步枪子弹逆时针旋转一样。如果右手中微子被添加到标准模型中，那么中微子的质量可能与夸克和带电轻子的质量相同，该理论还将预测反中微子的存在。然而，即使没有右手中微子，有质量的中微子也是可能的，前提是中微子是它自己的反粒子。这样的质量后来被称为马约拉纳质量，以西西里物理学家埃托雷·马约拉纳的名字命名。但目前的标准模型禁止这种马约拉纳质量。这些关于中微子性质的微妙理论争论现在已经浮出水面，因为探测来自太阳的中微子以及由宇宙射线产生的大气中微子的实验结果表明，它们毕竟有质量。这些结果随后被来自核反应堆和束流的中微子的地面来源所证实。关于中微子质量和混合物的实验信息意味着超越标准模型的新物理，关于这些结果的理论含义已经有了很多活动。解释小中微子质量的一种有吸引力的机制是由Peter Minkowski于1977年提出的所谓的拉锯机制，1979年由在美国工作的Murray Gell-Mann、Pierre Ramond和Richard Slansky提出，并由东京大学的Tsutomu Yanagida独立提出。这个想法是将右手中微子引入标准模型，这些中微子是马约拉纳型粒子，具有非常重的质量，可能与标准模型的三种力统一的大质量尺度有关。海森堡测不准原理允许能量守恒在很小的时间间隔内被违反，然后允许左手中微子在短暂时间内自发转换为重的右手中微子，然后恢复为左手中微子。这导致观测到的左手中微子的马约拉纳质量非常小，它的微小与右手中微子的重量有关，很像跳蚤和大象栖息在拉锯机的两端。对小中微子质量的另一种解释来自于我们所知的三维以外的额外维度的概念，其动机是理论上试图将标准模型扩展到包括引力。额外的维度是在非常小的范围内“卷起来”的，因此它们通常是看不到的。这项提议的目的是让英国的理论家和实验者能够召开会议，讨论与中微子物理有关的最新理论和实验结果，并有望形成或促进新的想法和合作。

In 1930, the Austrian physicist Wolfgang Pauli proposed the existence of particles called neutrinos as a ``desperate remedy'' to account for the missing energy in a type of radioactivity called beta decay. He deduced that some of the energy must have been taken away by a new particle emitted in the decay process, the neutrino. Since then, after decades of painstaking experimental and theoretical work, neutrinos have become enshrined as an essential part of the accepted quantum description of fundamental particles and forces, the Standard Model of Particle Physics. This is a highly successful theory in which elementary building blocks of matter are divided into three generations of two kinds of particle - quarks and leptons. It also includes three of the fundamental forces of Nature, but does not include gravity. The leptons consist of the charged electron, muon and tau, together with three electrically neutral particles - the electron neutrino, muon neutrino and tau neutrino. Unlike the case for quarks and charged leptons, however, the Standard Model predicts that neutrinos have no mass! This might seem curious for a matter particle, but the Standard Model predicts that neutrinos always have a left handed spin - rather like rifle bullets which spin counter clockwise to the direction of travel. If right-handed neutrinos were to be added to the Standard Model, then neutrinos could have the same sort of masses as the quarks and charged leptons, and the theory would also predict the existence of antineutrinos. However, even without right-handed neutrinos, neutrinos with mass are possible, providing that the neutrino is its own antiparticle. Such a mass is then called a Majorana mass, named after the Sicilian physicist, Ettore Majorana. But the current Standard Model forbids such Majorana masses. These subtle theoretical arguments about the nature of neutrinos have now come to the fore, as the results from experiments detecting neutrinos from the Sun, as well as atmospheric neutrinos produced by cosmic rays, suggest that they do have mass after all. These results have subsequently been confirmed by terrestrial sources of neutrinos from nuclear reactors and beams. Experimental information on neutrino masses and mixings implies new physics beyond the Standard Model, and there has been much activity on the theoretical implications of these results. An attractive mechanism for explaining small neutrino masses is the so-called see-saw mechanism proposed in 1977 by Peter Minkowski and 1979 by Murray Gell-Mann, Pierre Ramond and Richard Slansky working in the U.S., and independently by Tsutomu Yanagida of Tokyo University. The idea is to introduce right-handed neutrinos into the Standard Model which are Majorana-type particles with very heavy masses, possibly associated with large mass scale at which the three forces of the Standard Model unify. The Heisenberg Uncertainty Principle, which allows energy conservation to be violated on small time intervals, then allows a left-handed neutrino to convert spontaneously into a heavy right handed neutrino for a brief moment before reverting back to being a left-handed neutrino. This results in the very small observed Majorana mass for the left-handed neutrino, its smallness being associated with the heaviness of the right-handed neutrino, rather like a flea and an elephant perched on either end of a see-saw. An alternative explanation of small neutrino masses comes from the concept of extra dimensions beyond the three that we know of, motivated by theoretical attempts to extend the Standard Model to include gravity. The extra dimensions are 'rolled up' on a very small scale so that they are not normally observable. The purpose of this proposal is to enable UK theorists and experimenters to hold meetings in which the latest theories and experimental results relating to neutrino physics can be discussed, and hopefully new ideas and collaborations can be formed or fostered.