• Discriminating between Thermal and Nonthermal Cosmic Relic Neutrinos through Annual Modulation at PTOLEMY

    分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-11-10

    摘要: If massive neutrinos are Dirac particles, the proposed PTOLEMY experiment will hopefully be able to discover cosmic neutrino background via e+3H ! 3He+e􀀀 with a capture rate of 􀀀D 4 yr􀀀1. Recently, it has been pointed out that right-handed com-ponents of Dirac neutrinos could also be copiously produced in the early Universe and become an extra thermal or nonthermal ingredient of cosmic relic neutrinos, enhancing the capture rate to 􀀀D 5:1 yr􀀀1 or 􀀀D 6:1 yr􀀀1. In this work, we investigate the possibility to distinguish between thermal and nonthermal spectra of cosmic relic neu-trinos by measuring the annual modulation of the capture rate. For neutrino masses of 0:1 eV, we have found the amplitude of annual modulation in the standard case is M 0:05%, which will be increased to 0:1% and 0:15% in the presence of additional thermal and nonthermal right-handed neutrinos, respectively. The future detection of such a modulation will be helpful in understanding the Majorana or Dirac nature of massive neutrinos.

  • Cosmology-friendly time-varying neutrino masses via the sterile neutrino portal

    分类: 天文学 >> 天文学 提交时间: 2023-02-19

    摘要: We investigate a consistent scenario of time-varying neutrino masses, and discuss its impact on cosmology, beta decay, and neutrino oscillation experiments. Such time-varying masses are assumed to be generated by the coupling between a sterile neutrino and an ultralight scalar field, which in turn affects the light neutrinos by mixing. Besides, the scalar could act as an ultralight dark matter candidate. We demonstrate how various cosmological bounds, such as those coming from Big Bang nucleosynthesis, the cosmic microwave background, as well as large scale structures, can be evaded in this model. This scenario can be further constrained using multiple terrestrial experiments. In particular, for beta-decay experiments like KATRIN, non-trivial distortions to the electron spectrum can be induced, even when time-variation is fast and gets averaged out. Furthermore, the presence of time-varying masses of sterile neutrinos will alter the interpretation of light sterile neutrino parameter space in the context of the reactor and gallium anomalies. In addition, we also study the impact of such time-varying neutrino masses on results from the BEST collaboration, which have recently strengthened the gallium anomaly. If confirmed, we find that the time-varying neutrino mass hypothesis could give a better fit to the recent BEST data.