Measurement of the neutron lifetime using a hybrid magnetic trap for ultra-cold neutrons

中子寿命τn是一个基本的观测值，它不仅决定了大爆炸核合成中轻元素的丰度，而且也是理解粒子物理标准模型框架内弱相互作用的关键因素。在这方面，中子寿命是角相关性的最重要补充，角相关性是新仪器PERC的范围。最近的一个实验引用的不确定度只有0.8秒，产生了一个令人困惑的情况：它的τn结果偏离了以前的世界平均值超过7秒。由于过去大多数精确的实验都是将超冷中子（UCN）储存在材料瓶中，因此这种差异需要采用不同的系统方法。因此，我们的目标是在此资助期内测量τn，精度远低于1 s，使用一种新的方法，在磁引力UCN阱中实时检测中子衰变产生的电子，并与新的高密度UCN源耦合。

The neutron lifetime τn is a basic observable that not only determines the light-element abundances in big-bang nucleosynthesis but is also a key ingredient for understanding weak interactions within the framework of the Standard Model of particle physics. In this respect the neutron lifetime is the most important complement to the angular correlations which are the scope of the new instrument PERC. A recent experiment with quoted uncertainty of only 0.8 seconds has generated a confusing situation: its result for τn deviates from the previous world average by more than seven seconds. Since most precise past experiments employed storage of ultra-cold neutrons (UCN) in material bottles, the discrepancy calls for an approach with different systematic. Our goal is thus to measure τn within this funding period with accuracy well below 1 s, using a novel method with live detection of electrons from neutron decay within a magneto-gravitational UCN trap, coupled to a new high-density UCN source.