PandaX-4T reports the first direct spectral search for scalar-mediated neutrino self-interactions in 136Xe double beta decay, setting new upper limits for mediator masses below 2 MeV/c².
Interacting neutrinos in cosmology: exact description and constraints
6 Pith papers cite this work. Polarity classification is still indexing.
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abstract
We consider the impact of neutrino self-interactions described by an effective four-fermion coupling on cosmological observations. Implementing the exact Boltzmann hierarchy for interacting neutrinos first derived in [arxiv:1409.1577] into the Boltzmann solver CLASS, we perform a detailed numerical analysis of the effects of the interaction on the cosmic microwave background (CMB) anisotropies, and compare our results with known approximations in the literature. While we find good agreement between our exact approach and the relaxation time approximation used in some recent studies, the popular $\left( c_{\text{eff}}^2,c_{\text{vis}}^2 \right)$-parameterisation fails to reproduce the correct scale dependence of the CMB temperature power spectrum. We then proceed to derive constraints on the effective coupling constant $G_{\text{eff}}$ using currently available cosmological data via an MCMC analysis. Interestingly, our results reveal a bimodal posterior distribution, where one mode represents the standard $\Lambda$CDM limit with $G_{\rm eff} \lesssim 10^8 \, G_{\rm F}$, and the other a scenario in which neutrinos self-interact with an effective coupling constant $G_{\rm eff} \simeq 3 \times 10^9 \, G_{\rm F}$.
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representative citing papers
A new scheme for the neutrino collision term valid from light to heavy mediator regimes, with smooth transition as the universe cools, for scalar-mediated NSI in Dirac and Majorana cases.
Ultralight scalar dark matter amplifies the lepton-flavor-violating muon-to-positron conversion rate via an effective Majorana mass m_μe, yielding new constraints on flavor-off-diagonal neutrino couplings from SINDRUM II, COMET, and Mu2e bounds.
Final Planck CMB data confirms the flat 6-parameter ΛCDM model with Ω_c h² = 0.120 ± 0.001, Ω_b h² = 0.0224 ± 0.0001, n_s = 0.965 ± 0.004, τ = 0.054 ± 0.007, H_0 = 67.4 ± 0.5 km/s/Mpc, and no strong evidence for extensions.
Fisher forecasts indicate that Lyα-21cm cross-spectra with PUMA and CMB data can improve constraints on neutrino self-interaction strength G_eff by 1-2 orders of magnitude over CMB alone.
Presents the science case, reference design, and project plan for the CMB-S4 ground-based CMB experiment.
citing papers explorer
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Probing scalar-neutrino and scalar-dark-matter interactions with PandaX-4T
PandaX-4T reports the first direct spectral search for scalar-mediated neutrino self-interactions in 136Xe double beta decay, setting new upper limits for mediator masses below 2 MeV/c².
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Towards a complete scheme of cosmological neutrino self-interactions: Collision term for a wide range of mediator masses
A new scheme for the neutrino collision term valid from light to heavy mediator regimes, with smooth transition as the universe cools, for scalar-mediated NSI in Dirac and Majorana cases.
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Amplifying muon-to-positron conversion in nuclei with ultralight dark matter
Ultralight scalar dark matter amplifies the lepton-flavor-violating muon-to-positron conversion rate via an effective Majorana mass m_μe, yielding new constraints on flavor-off-diagonal neutrino couplings from SINDRUM II, COMET, and Mu2e bounds.
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Planck 2018 results. VI. Cosmological parameters
Final Planck CMB data confirms the flat 6-parameter ΛCDM model with Ω_c h² = 0.120 ± 0.001, Ω_b h² = 0.0224 ± 0.0001, n_s = 0.965 ± 0.004, τ = 0.054 ± 0.007, H_0 = 67.4 ± 0.5 km/s/Mpc, and no strong evidence for extensions.
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Neutrino self-interactions in post-reionization era: Lyman-$\alpha$, 21-cm and cross-spectra
Fisher forecasts indicate that Lyα-21cm cross-spectra with PUMA and CMB data can improve constraints on neutrino self-interaction strength G_eff by 1-2 orders of magnitude over CMB alone.
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CMB-S4 Science Case, Reference Design, and Project Plan
Presents the science case, reference design, and project plan for the CMB-S4 ground-based CMB experiment.