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arXiv 2001.06522hep-phhep-ex
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$(g-2)_μ$和KOTO反常的轻标量解释

A Light Scalar Explanation of $(g-2)_μ$ and the KOTO Anomaly

Jia Liu, Navin McGinnis, Carlos E. M. Wagner, Xiao-Ping Wang

摘要:

KOTO实验最近进行了一项寻找中性K介子衰变为中性π介子和一对中微子的研究。在KOTO信号区观测到三个事件,预计背景值约为0.05。由于没有发现系统误差的明确信号,因此衰变$K_{L}\rightarrowπ^0ν\barν$中的过剩事件是相当有趣的。一种可能的解释是存在一个质量为π质量量级的标量$ϕ$,并诱导出模拟观测信号的衰变$K_L \to π^0 ϕ$;一个质量为π质量量级的标量和一个标准模型希格斯耦合量级的μ子耦合也可以解释μ子磁矩异常$(g-2)_μ$。我们建立在这些事实表明,一个轻的单重标量与轻子和夸克的耦合,因为在两个希格斯二重态模型中与希格斯态混合引起的,可能会导致这两个异常的解释。更具体地说,我们表明,这是在所谓的X型模型中的情况下,轻子和夸克耦合到两个不同的希格斯双重态,并为标量质量的范围在40和70兆电子伏之间。由于需要相对较大的耦合到轻子,以适应$(g-2)_μ$,标量寿命意外地落入亚纳秒范围内,这是必要的,以逃避严重的质子束流收集实验和天体物理学的限制,虽然它变得敏感的限制,从电子束流收集实验。讨论了该模型的其他唯象性质。

英文摘要:

The KOTO experiment has recently performed a search for neutral Kaons decaying into neutral pions and a pair of neutrinos. Three events were observed in the KOTO signal region, with an expected background of about 0.05. Since no clear signal of systematic errors have been found, the excess of events in the decay $K_{L}\rightarrowπ^0ν\barν$ is quite intriguing. One possibility to explain this anomaly would be the presence of a scalar $ϕ$ with mass of the order of the pion mass and inducing decays $K_L \to π^0 ϕ$ which mimic the observed signal.A scalar with mass of the order of the pion mass and a coupling to muons of the order of the Standard Model Higgs coupling could also explain the muon anomalous magnetic moment anomaly $(g-2)_μ$. We built on these facts to show that a light singlet scalar with couplings to the leptons and quarks as the ones induced by mixing with Higgs states in two Higgs doublet models may lead to an explanation of both anomalies. More specifically, we show that this is the case in the so-called type-X models in which leptons and quarks couple to two different Higgs doublets, and for scalar masses that are in the range between 40 and 70 MeV. Due to the relatively large coupling to leptons required to fit $(g-2)_μ$, the scalar lifetime accidentally falls into the sub-nanosecond range which is essential to evade the severe proton beam dump experiments and astrophysical constraints, though it becomes sensitive to constraints from electron beam dump experiments. The additional phenomenological properties of this model are discussed.

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