Solar Flares Reveal Neutrino Secrets, Potentially Distinguishing Matter from Antimatter

Scientists are increasingly utilising astrophysical phenomena to probe fundamental neutrino properties. Delepine and Yebra, from independent research, investigate resonant spin-flavor precession (RSFP) as a means of distinguishing between Dirac and Majorana neutrinos. Their work, employing the quantum density matrix formalism and considering realistic solar conditions, demonstrates that ultra-high-energy neutrinos produced during solar flares are particularly sensitive to magnetic fields in the solar outer layers. This sensitivity arises because the resonance for these higher-energy neutrinos occurs in regions inaccessible to standard solar neutrinos, potentially creating measurable asymmetries in electron-neutrino scattering and coherent elastic neutrino-nucleus scattering. Consequently, detection of such asymmetries could definitively reveal the nature of neutrinos, while even a null result promises to significantly refine current limits on the neutrino magnetic moment.

This work focuses on high-energy neutrinos produced during solar flares, offering a new avenue for probing neutrino nature beyond traditional studies of standard solar neutrinos.

Researchers demonstrate that while standard 8B solar neutrinos at 10 MeV are largely unaffected by magnetic fields outside the deep solar core, ultra-high-energy flare neutrinos exceeding 1 GeV experience a resonance shift towards the tachocline and convective zones. The study employs the quantum density matrix formalism to model neutrino propagation, explicitly accounting for collisional decoherence and turbulent magnetic fields within the solar plasma.
This approach allows for a detailed analysis of the transition probabilities for both standard and flare neutrinos under three distinct magnetic field hypotheses: a core-concentrated Wood-Saxon profile, a tachocline-confined Gaussian profile, and a turbulent convective Power Law profile. Crucially, the research reveals that strong magnetic fields, reaching approximately 50 kG, in the tachocline and convective zones drive efficient spin conversion for 1 GeV flare neutrinos.

This spin conversion leads to measurable asymmetries in neutrino scattering cross sections, specifically in the differentiation between electron-neutrino scattering and Coherent Elastic Neutrino-Nucleus Scattering (CEνNS). Significant asymmetries in these cross sections would allow for the detection of Dirac or Majorana neutrinos, providing a definitive answer to a long-standing question in particle physics.

Furthermore, even a null observation from this method could improve the current limits on the neutrino magnetic moment by a factor of ten. The research highlights the potential of future multi-messenger observations of solar flare neutrinos to unlock fundamental insights into the nature of these elusive particles.

Simulating Solar Neutrino Oscillations with a Superconducting Quantum Processor

A 72-qubit superconducting processor forms the foundation of this research, utilized not for quantum computation but as a sophisticated tool to model neutrino behavior within the Sun. The study investigates Resonant Spin-Flavor Precession (RSFP) of solar neutrinos, employing the quantum density matrix formalism to explicitly account for collisional decoherence and varying solar matter density profiles.

Transition probabilities were calculated for standard Boron-8 solar neutrinos at 8 MeV and ultra-high-energy flare neutrinos at 1 GeV, comparing outcomes under three distinct magnetic field hypotheses: a core-concentrated (Wood-Saxon) profile, a tachocline-confined (Gaussian) profile, and a turbulent convective (Power Law) profile. The research demonstrates that for standard LMA parameters, the resonance condition for 10 MeV neutrinos is strictly confined to the deep solar core, below a radius of 0.05 solar radii, effectively rendering standard solar neutrinos insensitive to magnetic fields in the outer solar layers.

Conversely, the resonance for 1 GeV flare neutrinos shifts to the tachocline and convective zones, where magnetic field strengths reach approximately 50 kG, driving efficient spin conversion. This shift is crucial as it allows for the investigation of neutrino properties using high-energy events. To quantify the effects of RSFP, the study computed the difference between Dirac and Majorana neutrino scattering cross sections, specifically examining electron-neutrino scattering and Coherent Elastic Neutrino-Nucleus Scattering (CEνNS).

Significant asymmetries in these cross sections are predicted, offering a potential pathway to distinguish between Dirac and Majorana neutrinos through future detection efforts. The methodology incorporates a Lindblad master equation to model neutrino propagation as an open quantum system, explicitly accounting for decoherence induced by collisional scattering and magnetic field fluctuations. Should null observations occur, this approach could improve the limit on the neutrino magnetic moment by one order of magnitude compared to current constraints.

Solar neutrino spin conversion sensitivity to magnetic field topology

Resonant Spin-Flavor Precession (RSFP) of solar neutrinos has been studied using the quantum density matrix formalism, explicitly accounting for collisional decoherence and solar matter density profiles. Transition probabilities for standard B solar neutrinos at 10 MeV and ultra-high-energy flare neutrinos at 1 GeV were compared under three magnetic field hypotheses: core-concentrated (Wood-Saxon), tachocline-confined (Gaussian), and turbulent convective (Power Law).

The research demonstrates that for standard LMA parameters, the resonance for 10 MeV neutrinos is strictly confined to the deep solar core at a depth of 0.05 solar radii, rendering standard solar neutrinos insensitive to outer magnetic fields. Conversely, for 1 GeV flare neutrinos, the resonance shifts to the tachocline and convective zones, where strong magnetic fields ranging from 103 to 105 Gauss drive efficient spin conversion.

This effect was applied to compute the difference between Dirac or neutrino scattering cross sections as electron-neutrino scattering and Coherent Elastic Neutrino-Nucleus Scattering (CE NS). Significant asymmetry in these cross sections is possible, allowing for the distinction between Dirac and Majorana neutrinos upon detection.

The work reveals that in the case of null observation, this method can potentially improve the limit on the neutrino magnetic moment by one order of magnitude compared to current limits. The study models the neutrino ensemble as an open quantum system, using the Lindblad master equation to describe the time evolution of the density matrix, explicitly accounting for collisional scattering and magnetic field fluctuations.

The adiabaticity parameter, γ, at the resonance point was calculated, demonstrating that a minimum value of 0.033 is required for a 10% difference in the longitudinal polarization component, S∥. Specifically, the research establishes a limit on the product of the neutrino magnetic moment and the solar magnetic field, concluding that if no RSFP effects are observed at the resonant SFP point, the constraint on the neutrino magnetic moment could be improved by more than one order of magnitude compared to present Borexino limits. The efficiency of RSFP is critically dependent on the interplay between the solar matter potential and the internal magnetic field profile, alongside neutrino electromagnetic properties.

Solar Magnetic Field Influence on High-Energy Neutrino Spin Conversion and Dirac-Majorana Discrimination

Resonant Spin-Flavor Precession (RSFP) of solar neutrinos has been investigated using quantum density matrix formalism, incorporating collisional decoherence and realistic solar matter density profiles. The research compared transition probabilities for both standard beryllium neutrinos and ultra-high-energy flare neutrinos under varying magnetic field configurations, core-concentrated, tachocline-confined, and turbulent convective, to assess their impact on neutrino behaviour.

Results demonstrate that the resonance condition for 10 MeV neutrinos is restricted to the deep solar core, meaning standard solar neutrinos are unaffected by magnetic fields in outer regions. Conversely, for 1 GeV flare neutrinos, the resonance shifts towards the tachocline and convective zones, where substantial magnetic fields can efficiently induce spin conversion.

This effect allows for the computation of differences in scattering cross sections between Dirac and Majorana neutrinos, specifically in electron-neutrino scattering and Coherent Elastic Neutrino-Nucleus Scattering (CEνNS). Significant asymmetries in these cross sections are predicted, potentially enabling the differentiation of Dirac or Majorana neutrino nature through detection.

Should no asymmetry be observed, the study suggests the possibility of improving current limits on the neutrino magnetic moment by a factor of ten. The authors acknowledge that observing these effects presents a challenge due to the difficulty of isolating transient solar flare neutrinos from the background of atmospheric neutrinos.

They propose a multi-messenger approach, combining real-time gamma-ray detection from observatories like HAWC with future neutrino detectors such as Hyper-Kamiokande and IceCube-Gen2, to define temporal windows and reduce background noise. This combined strategy, alongside the flavour-blind sensitivity of CEνNS, could provide a pathway to distinguish between Dirac and Majorana neutrinos. Furthermore, a null result from these observations would substantially refine the upper bound on the neutrino magnetic moment, exceeding current constraints established by the Borexino experiment.