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1. The TeV Diffuse Cosmic Neutrino Spectrum and the Nature of Astrophysical Neutrino Sources

   https://doi.org/10.3847/1538-4357/ac7649  

   Fang, Ke; Gallagher, John S.; Halzen, Francis (July 2022, The Astrophysical Journal)

   Abstract The diffuse flux of cosmic neutrinos has been measured by the IceCube Observatory from TeV to PeV energies. We show that an improved characterization of this flux at lower energies, TeV and sub-TeV, reveals important information on the nature of the astrophysical neutrino sources in a model-independent way. Most significantly, it could confirm the present indications that neutrinos originate in cosmic environments that are optically thick to GeV–TeV γ -rays. This conclusion will become inevitable if an uninterrupted or even steeper neutrino power law is observed in the TeV region. In such γ -ray-obscured sources, the γ -rays that inevitably accompany cosmic neutrinos will cascade down to MeV–GeV energies. The requirement that the cascaded γ -ray flux accompanying cosmic neutrinos should not exceed the observed diffuse γ -ray background puts constraints on the peak energy and density of the radiation fields in the sources. Our calculations inspired by the existing data suggest that a fraction of the observed diffuse MeV–GeV γ -ray background may be contributed by neutrino sources with intense radiation fields that obscure the high-energy γ -ray emission accompanying the neutrinos. 

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2. Neutrino forces in neutrino backgrounds

   https://doi.org/10.1007/JHEP02(2023)092  

   Ghosh, Mitrajyoti; Grossman, Yuval; Tangarife, Walter; Xu, Xun-Jie; Yu, Bingrong (February 2023, Journal of High Energy Physics)

   A bstract The Standard Model predicts a long-range force, proportional to $$ {G}_F^2/{r}^5 $$ G F 2 / r 5 , between fermions due to the exchange of a pair of neutrinos. This quantum force is feeble and has not been observed yet. In this paper, we compute this force in the presence of neutrino backgrounds, both for isotropic and directional background neutrinos. We find that for the case of directional background the force can have a 1 /r dependence and it can be significantly enhanced compared to the vacuum case. In particular, background effects caused by reactor, solar, and supernova neutrinos enhance the force by many orders of magnitude. The enhancement, however, occurs only in the direction parallel to the direction of the background neutrinos. We discuss the experimental prospects of detecting the neutrino force in neutrino backgrounds and find that the effect is close to the available sensitivity of the current fifth force experiments. Yet, the angular spread of the neutrino flux and that of the test masses reduce the strength of this force. The results are encouraging and a detailed experimental study is called for to check if the effect can be probed. 

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3. eV-Scale Sterile Neutrino Search Using Eight Years of Atmospheric Muon Neutrino Data from the IceCube Neutrino Observatory

   https://doi.org/10.1103/PhysRevLett.125.141801  

   Aartsen, M. G.; Abbasi, R.; Ackermann, M.; Adams, J.; Aguilar, J. A.; Ahlers, M.; Ahrens, M.; Alispach, C.; Amin, N. M.; Andeen, K.; et al (September 2020, Physical Review Letters)

   null (Ed.)
4. The neutrino force in neutrino backgrounds: Spin dependence and parity-violating effects

   https://doi.org/10.1007/JHEP07(2024)107  

   Ghosh, Mitrajyoti; Grossman, Yuval; Tangarife, Walter; Xu, Xun-Jie; Yu, Bingrong (July 2024, Journal of High Energy Physics)

   A<sc>bstract</sc> The neutrino force results from the exchange of a pair of neutrinos. A neutrino background can significantly influence this force. In this work, we present a comprehensive calculation of the neutrino force in various neutrino backgrounds with spin dependence taken into account. In particular, we calculate the spin-independent and spin-dependent parity-conserving neutrino forces, in addition to the spin-dependent parity-violating neutrino forces with and without the presence of a neutrino background for both isotropic and anisotropic backgrounds. Compared with the vacuum case, the neutrino background can effectively violate Lorentz invariance and lead to additional parity-violating terms that are not suppressed by the velocity of external particles. We estimate the magnitude of the effect of atomic parity-violation experiments, and it turns out to be well below the current experimental sensitivity. 

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5. Impact of late-time neutrino emission on the diffuse supernova neutrino background

   https://doi.org/10.1103/PhysRevD.106.043026  

   Ekanger, Nick; Horiuchi, Shunsaku; Kotake, Kei; Sumiyoshi, Kohsuke (August 2022, Physical Review D)