Measurement of the neutron lifetime using a magneto-gravitational trap and in situ detection-猫眼课题宝

DOI：

10.1126/science.aan8895

发表时间：

2017-07

期刊：

Science

影响因子：

56.9

通讯作者：

中科院分区：

综合性期刊1区

文献类型：

作者：

R. Pattie;N. Callahan;C. Cude-Woods;E. Adamek;L. Broussard;S. Clayton;S. Currie;E. Dees;X. Ding;E. M. Engel;D. Fellers;W. Fox;P. Geltenbort;K. Hickerson;M. Hoffbauer;A. Holley;A. Komives;C-Y. Liu;S. W. T. MacDonald;M. Makela;C. Morris;J. Ortiz;J. Ramsey;D. Salvat;A. Saunders;S. Seestrom;E. Sharapov;S. Sjue;Z. Tang;J. Vanderwerp;B. Vogelaar;P. Walstrom;Z. Wang;W. Wei;H. Weaver;J. Wexler;T. Womack;A. R. Young;B. Zeck

中子能活多久？质子的寿命比宇宙的年龄还要长，而自由中子的衰变寿命只有15分钟。测量中子的确切寿命是令人惊讶的棘手;把它们放在容器中并监测它们的衰变可能会导致错误，因为一些中子会由于与容器壁的相互作用而丢失。为了克服这个问题，Pattie等人测量了超冷极化中子被磁场悬浮的阱中的寿命，排除了与阱壁的相互作用（参见Mumm的观点）。中子寿命的更精确测定将有助于我们理解大爆炸后第一个原子核是如何形成的。《科学》，本期第627页;另见第605页超冷极化中子悬浮在阱中，以减少系统的不确定性来测量它们的寿命。中子平均寿命τn的精确值在核物理、粒子物理和宇宙学中起着重要的作用。它被用来预测原始宇宙中质子与氦原子的比例，并搜索粒子物理学标准模型之外的物理。我们消除了在以前的陷阱实验中存在的损失机制，通过使用排斥磁场梯度使极化超冷中子悬浮在非对称存储陷阱的表面上方，使得存储的中子不与材料陷阱壁相互作用。由于采用了这种方法和原位中子探测器，这里报告的寿命[877.7 ± 0.7（stat）+0.4/-0.2（sys）s]不需要比引用的不确定度更大的修正。

How long does a neutron live? Unlike the proton, whose lifetime is longer than the age of the universe, a free neutron decays with a lifetime of about 15 minutes. Measuring the exact lifetime of neutrons is surprisingly tricky; putting them in a container and monitoring their decay can lead to errors because some neutrons will be lost owing to interactions with the container walls. To overcome this problem, Pattie et al. measured the lifetime in a trap where ultracold polarized neutrons were levitated by magnetic fields, precluding interactions with the trap walls (see the Perspective by Mumm). This more precise determination of the neutron lifetime will aid our understanding of how the first nuclei formed after the Big Bang. Science, this issue p. 627; see also p. 605 Ultracold polarized neutrons are levitated in a trap to measure their lifetime with reduced systematic uncertainty. The precise value of the mean neutron lifetime, τn, plays an important role in nuclear and particle physics and cosmology. It is used to predict the ratio of protons to helium atoms in the primordial universe and to search for physics beyond the Standard Model of particle physics. We eliminated loss mechanisms present in previous trap experiments by levitating polarized ultracold neutrons above the surface of an asymmetric storage trap using a repulsive magnetic field gradient so that the stored neutrons do not interact with material trap walls. As a result of this approach and the use of an in situ neutron detector, the lifetime reported here [877.7 ± 0.7 (stat) +0.4/–0.2 (sys) seconds] does not require corrections larger than the quoted uncertainties.

Measurement of the neutron lifetime using a magneto-gravitational trap and in situ detection

文献摘要

被引文献

相似文献