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arXiv 1608.03591hep-phhep-exnucl-exnucl-th
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铍核衰变中17 MeV异常的粒子物理模型

Particle Physics Models for the 17 MeV Anomaly in Beryllium Nuclear Decays

Jonathan L. Feng, Bartosz Fornal, Iftah Galon, Susan Gardner, Jordan Smolinsky, Tim M. P. Tait, Philip Tanedo

摘要:

用一种新的粒子解释很好地拟合了激发态~ 8Be核衰变中的$σ$异常。在以前的分析中,我们表明,17兆电子伏的疏质子规范玻色子提供了一个粒子物理解释的异常与所有现有的限制。在这里,我们开始与8Be衰变的内部对创建的物理和观察到的异常的特点进行审查。为了发展其粒子的解释,我们提供了一个有效的运营商分析激发8Be衰变到粒子与各种自旋和宇称,这些考虑排除简单的模型与标量粒子。我们讨论了所需的耦合规范玻色子给出所观察到的信号,突出了显着的依赖精确质量的玻色子和同位旋混合和破碎的效果。我们提出了无异常扩展的标准模型,包含质子憎规范玻色子与所需的耦合来解释8Be异常。在第一个模型中,新的力载体是一个与光子动力学混合的U(1)B规范玻色子;在第二个模型中,它是一个具有类似动力学混合的U(1)(B-L)规范玻色子。在这两种情况下,模型预测相对较大的带电轻子耦合~ 0.001,可以解决μ子异常磁矩的差异,并服从许多实验探测。该模型还包含矢量轻子在弱标度,可能会访问不久的未来大型强子对撞机搜索。

英文摘要:

The 6.8$σ$ anomaly in excited 8Be nuclear decays via internal pair creation is fit well by a new particle interpretation. In a previous analysis, we showed that a 17 MeV protophobic gauge boson provides a particle physics explanation of the anomaly consistent with all existing constraints. Here we begin with a review of the physics of internal pair creation in 8Be decays and the characteristics of the observed anomaly. To develop its particle interpretation, we provide an effective operator analysis for excited 8Be decays to particles with a variety of spins and parities and show that these considerations exclude simple models with scalar particles. We discuss the required couplings for a gauge boson to give the observed signal, highlighting the significant dependence on the precise mass of the boson and isospin mixing and breaking effects. We present anomaly-free extensions of the Standard Model that contain protophobic gauge bosons with the desired couplings to explain the 8Be anomaly. In the first model, the new force carrier is a U(1)B gauge boson that kinetically mixes with the photon; in the second model, it is a U(1)(B-L) gauge boson with a similar kinetic mixing. In both cases, the models predict relatively large charged lepton couplings ~ 0.001 that can resolve the discrepancy in the muon anomalous magnetic moment and are amenable to many experimental probes. The models also contain vectorlike leptons at the weak scale that may be accessible to near future LHC searches.

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