论文标题
QCD轴的信号为17 MeV/c^2：核转变和光中膜衰变
Signals of the QCD axion with mass of 17 MeV/c^2: nuclear transitions and light meson decays
论文作者
论文摘要
如果（i）主要与第一代SM费米子耦合，则QCD轴在O（10 MeV）的质量范围内保持实验性。 （ii）它会衰减到$ e^+ e^ - $，而短寿命$τ_a\ Lessim 10^{ - 13} \，$ s; （iii）它已抑制了等分离器耦合，即如果是恐惧症。 Remarkably, these are precisely the properties required to explain recently observed anomalies in nuclear de-excitations, to wit: the $e^+e^-$ emission spectra of isoscalar magnetic transitions of $^{8\!}$Be and $^{4\!}$He nuclei showed a "bump-like" feature peaked at $m_{e^+e^-}\sim 17$ MeV.在本文中，我们认为QCD轴上的壳发射（带有上述特性）为这些核能解脱中观察到的过量物质提供了极为充分的动机，兼容的解释。在其他测得的过渡中缺乏异常特征也自然解释了：恐惧轴的发射在等异载克磁过渡中被强烈抑制，并且在电过渡中被禁止。独立观察结果进一步证实了该QCD轴上假设：$ 2-3 \，σ$偏差在$γ（π^0 \ to e^+e^ - ）$中的测量中，从标准模型的理论期望中进行了。本文还包括对稀有光中衰减中各种轴子特征的详细估计，考虑到低倾斜的QCD共振交换所做的贡献，并且在罕见的Kaon衰减的情况下，$ΔS= 1 $ $ΔS= 1 $ octet的有效实现在手学扰动理论中增强。在低能量下强相互作用的有效描述的这些固有的不确定性会导致QCD轴的望子信号的预测有很大差异。尽管如此，此处获得的稀有中膜衰减率的估计范围可以在不久的将来以$η/η^\ Prime $和Kaon工厂进行探测。
The QCD axion remains experimentally viable in the mass range of O(10 MeV) if (i) it couples predominantly to the first generation of SM fermions; (ii) it decays to $e^+ e^-$ with a short lifetime $τ_a\lesssim 10^{-13}\,$s; and (iii) it has suppressed isovector couplings, i.e., if it is piophobic. Remarkably, these are precisely the properties required to explain recently observed anomalies in nuclear de-excitations, to wit: the $e^+e^-$ emission spectra of isoscalar magnetic transitions of $^{8\!}$Be and $^{4\!}$He nuclei showed a "bump-like" feature peaked at $m_{e^+e^-}\sim 17$ MeV. In this article, we argue that on-shell emission of the QCD axion (with the aforementioned properties) provides an extremely well-motivated, compatible explanation for the observed excesses in these nuclear de-excitations. The absence of anomalous features in other measured transitions is also naturally explained: piophobic axion emission is strongly suppressed in isovector magnetic transitions, and forbidden in electric transitions. This QCD axion hypothesis is further corroborated by an independent observation: a $2-3\,σ$ deviation in the measurement of $Γ(π^0\to e^+e^-)$ from the Standard Model theoretical expectation. This article also includes detailed estimations of various axionic signatures in rare light meson decays, which take into account contributions from low-lying QCD resonance exchange, and, in the case of rare Kaon decays, the possible effective implementations of $ΔS=1$ octet enhancement in chiral perturbation theory. These inherent uncertainties of the effective description of the strong interactions at low energies result in large variations in the predictions for hadronic signals of the QCD axion; in spite of this, the estimated ranges for rare meson decay rates obtained here can be probed in the near future in $η/η^\prime$ and Kaon factories.
