A parts-per-billion measurement of the antiproton magnetic moment
A parts-per-billion measurement of the antiproton magnetic moment
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DOI：
10.1038/nature24048
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发表时间：
2017-10-19
期刊：
影响因子：
64.8
通讯作者：
Ulmer, S.
中科院分区：
文献类型：
--
作者：
Smorra, C.;Sellner, S.;Ulmer, S.
对物质-反物质共轭的基本性质的精确比较提供了电荷-宇称-时间（CPT）不变性的敏感测试（1），这是一个重要的对称性，依赖于粒子物理学标准模型的基本假设。介子（2），轻子（3，4）和重子（5，6）的实验比较了物质-反物质共轭的不同性质，分数不确定度在十亿分之几或更好的水平。然而，到目前为止，我们只知道一个具体的量，它的不确定度在百万分之一的水平上（7，8）：反质子的磁矩，μ（（p）除以巴）。要高精度地测量μ（（p）/bar）是非常困难的，这是由于μ的固有的小;例如，它比正电子（3）的磁矩小660倍。在这里，我们报告了一个高精度的测量μ（（p）在酒吧）的单位的核磁子μ N的分数精度为1.5十亿分之一（68%的置信水平）。我们在一个先进的低温多潘宁阱系统中使用了双粒子谱方法。我们的结果mu（（p）over bar）= -2.7928473441（42）mu（N）（其中括号中的数字表示该值最后一位数字的68%置信区间）将先前最佳mu（p）over bar）测量（8）的精度提高了约350倍。测量值与质子磁矩（9）μ（（p）/bar）= 2.792847350（9）μ（N）一致，并符合CPT不变性。因此，这种测量将某些CPT破坏效应的大小限制在1.8 × 10（-24）千兆电子伏特以下，并将CPT奇数维5相互作用对质子-反质子磁矩的可能分裂限制在6 × 10（-12）玻尔磁子以下。
Precise comparisons of the fundamental properties of matter-antimatter conjugates provide sensitive tests of charge-parity-time (CPT) invariance(1), which is an important symmetry that rests on basic assumptions of the standard model of particle physics. Experiments on mesons(2), leptons(3,4) and baryons(5,6) have compared different properties of matter-antimatter conjugates with fractional uncertainties at the parts-per-billion level or better. One specific quantity, however, has so far only been known to a fractional uncertainty at the parts-per-million level(7,8): the magnetic moment of the antiproton, mu((p) over bar). The extraordinary difficulty in measuring mu((p) over bar) with high precision is caused by its intrinsic smallness; for example, it is 660 times smaller than the magnetic moment of the positron(3). Here we report a high-precision measurement of mu((p) over bar) in units of the nuclear magneton mu N with a fractional precision of 1.5 parts per billion (68% confidence level). We use a two-particle spectroscopy method in an advanced cryogenic multi-Penning trap system. Our result mu((p) over bar) = -2.7928473441(42) mu(N) (where the number in parentheses represents the 68% confidence interval on the last digits of the value) improves the precision of the previous best mu((p) over bar) measurement(8) by a factor of approximately 350. The measured value is consistent with the proton magnetic moment(9), mu((p) over bar) = 2.792847350(9) mu(N), and is in agreement with CPT invariance. Consequently, this measurement constrains the magnitude of certain CPT-violating effects(10) to below 1.8 x 10(-24) gigaelectronvolts, and a possible splitting of the protonantiproton magnetic moments by CPT-odd dimension-five interactions to below 6 x 10(-12) Bohr magnetons(11).