LBNE and the Fermilab Liquid Argon TPC Programme

最近在大型强子对撞机上发现希格斯玻色子是一项重大的技术和科学胜利，但这并不是故事的结束。粒子物理学中仍有许多悬而未决的问题。其中，也许最耐人寻味的问题是，为什么宇宙中的物质比反物质多。如果不是这样的话，基本上所有的粒子都会和它们的反粒子伙伴一起湮灭，宇宙将是一个非常不同的地方；不会有大尺度的结构，我们也不会在这里回答这个问题。对于这种物质--反物质的不对称性，一定有某种解释，无论答案是什么，它都意味着“违反了CP”，即物质的行为与反物质略有不同。在强相互作用粒子的衰变中观察到了CP破坏，但这不足以解释物质主导的宇宙。然而，有迹象表明，中微子可能通过一种名为瘦素发生的过程提供了答案。中微子领域的CP破坏可能代表着粒子物理学的下一个重大发现。中微子是中性的“幽灵”粒子，几乎不与物质相互作用。当中微子长途旅行时，它们会改变其性质，这一过程被称为中微子味道振荡，其中一种类型的中微子振荡成不同类型的中微子。中微子的CP破坏意味着中微子和反中微子的振荡速率略有不同。观察这种差异是实验粒子物理学面临的下一个重大挑战。LBNE实验是未来美国粒子物理计划的旗舰。它被设计用来发现中微子的CP破坏。一束强大的中微子将从芝加哥附近的费米实验室发射1300公里，射向南达科他州的一个巨大的地下探测器。这个地下探测器将在87K(-186摄氏度)的温度下包含5万吨液氮。液态Ar技术使中微子能够以“照片质量”的细节被探测到，标志着中微子实验的一项突破。在这项提案中，英国物理学家要求在三年内达到250万GB，以在LBNE实验中发挥主导作用，并开发液态Ar探测器技术。这一研发阶段将使英国成为这项令人难以置信的令人兴奋的实验的领先非美国合作伙伴。

The recent discovery of the Higgs boson at the LHC was a major technical and scientific triumph, but it is not the end of the story. There are still many unanswered questions in particle physics. Of these, perhaps the most intriguing is the question of why there is more matter in the Universe than antimatter. If this wasn't the case essentially all the particles would have annihilated with their antiparticle partners and the Universe would be a very different place; there would be no large-scale structure and we wouldn't be here to answer this question. There must be some explanation for this matter-antimatter asymmetry, and what ever the answer, it implies that "CP is violated", i.e. matter behaves slightly differently from antimatter. CP violation has been observed in the decays of strongly interacting particles, but this is not sufficient to explain the matter-dominated Universe. However, there are indications that neutrinos might provide the answer through a process called lepto-genesis. CP violation in the neutrino sector could represent the next major discovery in particle physics.Neutrinos are neutral "ghost" particles that hardly interact with matter. When the travel over large distances they change their nature, a process called neutrino flavour oscillations, whereby one type of neutrino oscillates into a different type. CP violation for neutrinos would imply that these oscillation rates are slightly different for neutrinos and antineutrinos. Observing this difference is the next big challenge to experimental particle physics. The LBNE experiment is the flagship of the future US particle physics programme. It is designed to discover CP violation for neutrinos. A powerful beam of neutrinos will be fired 1300 km from Fermilab, near Chicago, towards a huge underground detector in South Dakota. This underground detector will contain 50,000 tons of liquid argon at a temperature of 87 K (-186 degree Celsius). The liquid argon technology enables neutrinos to be detected with "photograph-quality" detail, marking a breakthrough in neutrino experiments. In this proposal, UK physicists are requesting £2.5M over three years to take leading roles in the LBNE experiment and to develop the liquid argon detector technology. This research and development phase will allow the UK to be the leading non-US partner in this incredibly exciting experiment.