Revisiting the Bound on Axion-Photon Coupling from Globular Clusters
Revisiting the Bound on Axion-Photon Coupling from Globular Clusters
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DOI：
10.1103/physrevlett.113.191302
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发表时间：
2014-11-04
影响因子：
8.6
通讯作者：
Straniero, Oscar
中科院分区：
文献类型：
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作者：
Ayala, Adrian;Dominguez, Inma;Straniero, Oscar
通过对39个球状星团的分析，我们得到了一个强的轴子-光子耦合g（a γ）的束缚。正如很久以前所认识到的，R参数，即，恒星核中光子转换产生的轴子会降低老星团中红巨星分支的水平恒星数比。在这方面，我们已经比较了测量的R与国家的最先进的恒星模型下获得的不同假设g（伽马）。我们表明，估计值的g（伽马）基本上取决于所采用的He质量分数Y，在以前的调查中往往被忽视的效果。作为我们研究的基准，我们得到了在95%置信水平下，H Ⅱ区O/H在相同范围内的He丰度的上限g（α γ）<0.66 × 10（-10）GeV~（-1）。这一结果显着改善了以前的分析的约束，是目前最强的限制在一个广泛的质量范围内的轴子光子耦合。
We derive a strong bound on the axion-photon coupling g(a gamma) from the analysis of a sample of 39 Galactic Globular Clusters. As recognized long ago, the R parameter, i.e., the number ratio of stars in horizontal over red giant branch of old stellar clusters, would be reduced by the axion production from photon conversions occurring in stellar cores. In this regard, we have compared the measured R with state-of-the-art stellar models obtained under different assumptions for g(a gamma). We show that the estimated value of g(a gamma) substantially depends on the adopted He mass fraction Y, an effect often neglected in previous investigations. Taking as a benchmark for our study the most recent determinations of the He abundance in H II regions with O/H in the same range of the Galactic Globular Clusters, we obtain an upper bound g(a gamma) < 0.66 x 10(-10) GeV-1 at 95% confidence level. This result significantly improves the constraints from previous analyses and is currently the strongest limit on the axion-photon coupling in a wide mass range.