Precision measurement of the angular correlation coefficient a in neutron beta-decay

中子β衰变角相关系数的精密测量

• 批准号: 335549596
• 负责人: Professor Dr. Werner Heil
• 金额: --
• 依托单位: Institut für Physik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2016
• 资助国家: 德国
• 起止时间: 2015-12-31 至 2020-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/335549596?language=en
• 关键词: Precision; measurement; angular; correlation; coefficient

In this proposal we ask for an expiry-financing of the aSPECT experiment. aSPECT has been funded in recent years via the DFG priority programme 1491 which expires end of 2016. In that period we were capable to perform a successful production run with the aSPECT spectrometer at ILL, Grenoble. We measured the electronantineutrino electron angular correlation coefficient a in ß decay of the free neutron via the recoil spectrum of the decay protons. A preliminary analysis of the data results in a relative uncertainty of ~ 0.7%. The total error bar is essentially determined by systematic errors which we want to investigate at the final analysis stage of our project in more detail. For that particle tracking simulations will be used for the recoil protons in the E und B field configurations of the aspect spectrometer. The final result will be published in peer reviewed journals. The present PDG value on a is known to 4%, relative. With our final result we will improve the accuracy on a significantly. Within the standard model of particle physics, a can be expressed as a function of lambda, the ratio of the weak axialvector and vector coupling constants. This value is an important input to calculate many semi-leptonic weak cross sections such as those relevant for big bang nucleosynthesis, stellar fusion and detection of neutrinos. It also enters the determination of the largest element of the CKM matrix which parameterizes mixing within the weak charged current interactions of quarks. On the other hand, a is sensitive to physics beyond the standard model as, e.g., scalar or tensor interactions. Our experiments will provide valuable input to global analyses of weak interaction parameters for applications and for tests of physics beyond the standard model.

在本提案中，我们要求为aSPECT实验提供到期融资。近年来，aSPECT通过DFG优先计划1491获得资助，该计划将于2016年底到期。在此期间，我们能够在格勒诺布尔的ILL进行成功的生产运行。我们通过衰变质子的反冲谱测量了自由中子衰变的电子-反中微子电子角相关系数a。对数据的初步分析得出了~ 0.7%的相对不确定度。总误差条本质上是由系统误差决定的，我们希望在项目的最终分析阶段更详细地研究系统误差。为此，粒子跟踪模拟将用于谱线谱仪E场和B场配置中的反冲质子。最终结果将发表在同行评议的期刊上。目前的PDG值已知为4%，相对而言。随着我们的最终结果，我们将大大提高准确度。在粒子物理的标准模型中，a可以表示为lambda的函数，lambda是弱轴向矢量和矢量耦合常数的比值。这个值是计算许多半轻子弱截面的重要输入，例如与大爆炸核合成、恒星聚变和中微子探测相关的截面。它还进入了CKM矩阵中最大元素的确定，该矩阵参数化了夸克弱带电电流相互作用中的混合。另一方面，a对标准模型之外的物理很敏感，例如标量或张量相互作用。我们的实验将为应用和标准模型之外的物理测试的弱相互作用参数的全局分析提供有价值的输入。