Dark-matter QCD-axion searches
Dark-matter QCD-axion searches
复制标题
暗物质 QCD 轴子搜索
DOI：
--
复制
发表时间：
2015
影响因子：
11.1
通讯作者：
L. Rosenberg
中科院分区：
文献类型：
--
作者：
L. Rosenberg
20世纪末，宇宙学成为一门精密科学。现在，在下个世纪初，描述我们的宇宙如何从大爆炸演化而来的参数通常只有百分之几的人知道。一个关键参数是宇宙的总质量密度。正常物质仅占总质量密度的一小部分。观测表明，这种额外的质量，即暗物质，是冷的（即在早期宇宙中非相对论性移动），并且与正常物质和辐射的相互作用即使有也微弱。目前还没有已知的这种基本粒子，因此强烈的假设是暗物质由大爆炸遗留下来的一种新型粒子遗迹组成。科学中最重要的问题之一是这种暗物质的性质。轴子是一种有吸引力的暗物质候选粒子。轴子是一种假设的基本粒子，是粒子物理标准模型简单而优雅的扩展，它消除了量子色动力学 (QCD) 中其他可观察到的 CP 破坏效应（其中 CP 是电荷反转 C 和宇称反转 P 的乘积）。质量为 10−(6–3) eV 的光轴子（看不见的轴子）与正常物质和辐射的耦合非常弱，因此在实验室中极难检测到。然而，这样的轴子是一种引人注目的暗物质候选者，因此是许多搜索的目标。与其他粒子暗物质候选者相比，轴子暗物质耦合和质量的合理范围受到严格限制。这种集中的搜索范围允许进行明确的搜索，如果不进行观察，就会严重质疑暗物质 QCD 轴子假说。轴子搜索使用了广泛的技术，实验灵敏度现已达到可能的暗物质轴子耦合和质量。本文是对当前一代敏感轴子搜索的选择性概述。并未讨论所有技术和实验，但我希望能让人了解当前寻找暗物质轴子的实验景观。
In the late 20th century, cosmology became a precision science. Now, at the beginning of the next century, the parameters describing how our universe evolved from the Big Bang are generally known to a few percent. One key parameter is the total mass density of the universe. Normal matter constitutes only a small fraction of the total mass density. Observations suggest this additional mass, the dark matter, is cold (that is, moving nonrelativistically in the early universe) and interacts feebly if at all with normal matter and radiation. There’s no known such elementary particle, so the strong presumption is the dark matter consists of particle relics of a new kind left over from the Big Bang. One of the most important questions in science is the nature of this dark matter. One attractive particle dark-matter candidate is the axion. The axion is a hypothetical elementary particle arising in a simple and elegant extension to the standard model of particle physics that nulls otherwise observable CP-violating effects (where CP is the product of charge reversal C and parity inversion P) in quantum chromo dynamics (QCD). A light axion of mass 10−(6–3) eV (the invisible axion) would couple extraordinarily weakly to normal matter and radiation and would therefore be extremely difficult to detect in the laboratory. However, such an axion is a compelling dark-matter candidate and is therefore a target of a number of searches. Compared with other particle dark-matter candidates, the plausible range of axion dark-matter couplings and masses is narrowly constrained. This focused search range allows for definitive searches, where a nonobservation would seriously impugn the dark-matter QCD-axion hypothesis. Axion searches use a wide range of technologies, and the experiment sensitivities are now reaching likely dark-matter axion couplings and masses. This article is a selective overview of the current generation of sensitive axion searches. Not all techniques and experiments are discussed, but I hope to give a sense of the current experimental landscape of the search for dark-matter axions.