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arXiv 2103.07167hep-ph
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用Majoron求解U(1)$_{L_μ-L_τ}$模型的Hubble张力

Resolving the Hubble tension in a U(1)$_{L_μ-L_τ}$ model with Majoron

Takeshi Araki, Kento Asai, Kei Honda, Ryuta Kasuya, Joe Sato, Takashi Shimomura, Masaki J. S. Yang

摘要:

本文探讨了在含有Majoron的U(1)$_{L_μ- L_τ}$模型中同时解决Hubble张力和$(g-2)_μ$反常的可能性。我们只关注的情况下,Majoron $ϕ$不存在于宇宙的开始,并通过中微子逆衰变$νν\to ϕ$后,电子-正电子湮灭。在这种情况下,新的规范玻色子$Z'$和Majoron $ϕ$对中微子物质有效数$N_{\rm eff}$的贡献可以在不同的时期计算。这些贡献被标记为$N'_{\rm eff}$的U(1)$_{L_μ- L_τ}$规范玻色子和$ΔN_{\rm eff}^\prime$的Majoron。利用各周期内轻粒子的温度和化学势的演化方程计算了有效数$N_{\rm eff} = N'_{\rm eff} + ΔN_{\rm eff}^\prime$。结果,我们发现,较重的$Z'$质量$m_{Z^\prime}$导致较小的$N_{\mathrm{eff}}^\prime$,并需要较大的$ΔN_{\mathrm{eff}}^\prime$来解决哈勃张力。因此,与以前的研究相比,可以分辨哈勃张力的参数区域略微向$m_{Z^\prime}$的较大值移动。

英文摘要:

In this paper, we explore possibilities of resolving the Hubble tension and $(g-2)_μ$ anomaly simultaneously in a U(1)$_{L_μ- L_τ}$ model with Majoron. We only focus on a case where the Majoron $ϕ$ does not exist at the beginning of the universe and is created by neutrino inverse decay $νν\to ϕ$ after electron-positron annihilation. In this case, contributions of the new gauge boson $Z'$ and Majoron $ϕ$ to the effective number of neutrino species $N_{\rm eff}$ can be calculated in separate periods. These contribution are labelled $N'_{\rm eff}$ for the U(1)$_{L_μ- L_τ}$ gauge boson and $ΔN_{\rm eff}^\prime$ for the Majoron. The effective number $N_{\rm eff} = N'_{\rm eff} + ΔN_{\rm eff}^\prime$ is evaluated by the evolution equations of the temperatures and the chemical potentials of light particles in each period. As a result, we found that the heavier $Z'$ mass $m_{Z^\prime}$ results in the smaller $N_{\mathrm{eff}}^\prime$ and requires the larger $ΔN_{\mathrm{eff}}^\prime$ to resolve the Hubble tension. Therefore, compared to previous studies, the parameter region where the Hubble tension can be resolved is slightly shifted toward the larger value of $m_{Z^\prime}$.

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