arXiv subjects

A. Yebra

Publications and source records attributed to A. Yebra.

5 recordsLinked to original sources

arXiv2026

Factorization vs. Non-Factorization: S-Matrix Corrections for Precision Neutrino Physics

The standard treatment of neutrino oscillations usually relies on factorization which assumes neutrino production, propagation, and detection are independent processes. As a consequence, the total probability is given by the product of production, oscillation and detection probabilities. As next-generation experiments are bringing neutrino physics to a high level of precision, the validity of this assumption must be checked. We present an S matrix treatment of the entire experimental chain, pion decay, neutrino propagation, and nucleon interaction, as a single, coherent quantum process. Our results reveal non-factorizable terms arising from spin and angular correlations between production and detection final states.In the $\Delta L=0$ channel, these corrections introduce a $\sim 1\%$ systematic shift in the energy spectrum and a non-vanishing azimuthal asymmetry, important to be taken into account for precision measurements of $\delta_{CP}$. For the $\Delta L=2$ Majorana channel, we demonstrate that the S-matrix formalism is generating an azimuthal modulation that provides a direct way to access to the Majorana CP phases, which remain hidden in standard factorized effective mass approximations.

hep-ph↗

arXiv2026

Solar Flares as a Probe of Neutrino Nature: Distinguishing Dirac and Majorana via Resonant Spin-Flavor Precession

Resonant Spin-Flavor Precession (RSFP) of solar neutrinos is studied using the quantum density matrix formalism, explicitly taking into account collisional decoherence and solar matter density profiles. The transition probabilities for standard $^8$B solar neutrinos ($E \approx 10$ MeV) and ultra-high-energy flare neutrinos ($E \gtrsim 1$ GeV) under three magnetic field hypotheses: core-concentrated (Wood-Saxon), tachocline-confined (Gaussian), and turbulent convective (Power Law) are compared. For standard LMA parameters, we show the resonance for 10 MeV neutrinos is strictly confined to the deep solar core ($r < 0.2 R_\odot$), 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 fields ($B \sim 50$ kG) drive efficient spin conversion. We apply this effect to compute the difference between Dirac or Majorana neutrino scattering cross section as electron-neutrino scattering and Coherent Elastic Neutrino-Nucleus Scattering (CE$\nu$NS). We show that significant asymmetry in these cross section are possible allowing in case of detection to distinguish between Dirac or Majorana neutrinos. In case of null observation, we show that this method can potentially improved the limit on the neutrino magnetic moment by one order to magnitude compared to current limits.

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arXiv2026

Distinguishing Dirac and Majorana Neutrinos: Resonant Spin-Flavor Precession of GeV-Scale Astrophysical Transients

We present a unified formalism to study the Resonant Spin-Flavor Precession (RSFP) of high-energy ($\sim 1$ GeV) transient astrophysical neutrinos as a probe of their fundamental Dirac or Majorana nature. Current MeV scale neutrino studies face stringent restrictions: efficient core RSFP for Dirac supernova neutrinos is excluded by SN1987A cooling bounds, while solar neutrino conversion is tightly constrained by Borexino data. We show that considering the 1 GeV energy scale accessible through solar flares modifies the resonance conditions. For 1 GeV solar flare neutrinos, the resonance shifts to the tachocline and convective zones, where toroidal magnetic fields ($B \sim 50$ kG) induce adiabatic spin flavor conversion. In contrast, for supernovae, to avoid the cooling constraints, the RSFP is moved from the core supernovae to the stellar envelope. As for non thermal 1 GeV supernova neutrinos, the resonance is located in the dilute stellar wind where magnetic fields are negligible, suppressing RSFP and preserving the flux, one can use these non-thermal neutrinos as a candle to calibrate our signal, reducing its dependence on astrophysical uncertainties. Evaluating these helicity transitions through a density matrix approach, we predict distinct asymmetries in Coherent Elastic Neutrino-Nucleus Scattering (CE$\nu$NS) and neutrino-electron scattering cross-sections for solar flare neutrinos and supernova neutrinos. Our proposal provides a viable method to distinguish Dirac from Majorana neutrinos and to probe magnetic moments down to $\mu_\nu \sim 10^{-14} \mu_B$.

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arXiv2026

The Dirac Majorana Confusion Theorem in the Presence of Flavor-Changing Neutral Currents: A CP-Filter Mechanism

The Practical Dirac Majorana Confusion Theorem(PDMCT) asserts that phenomenological differences between Dirac and Majorana neutrinos are kinematically suppressed by (neutrino mass/E)^2 in lepton number conserving processes. The PDMCT relies on standard lefthanded neutrino interactions, as in the SM, in which case Dirac and Majorana neutrinos are experimentally indistinguishable in lepton-number-conserving processes. Our scenario explicitly goes beyond these assumptions by introducing a neutral vector boson Zprime with CP-violating, flavor changing neutral current (FCNC) couplings, which generate observable Dirac Majorana differences while remaining fully consistent with the PDMCT. In strict accordance with the PDMCT, Fermi Dirac statistics dictate that the flavor-diagonal vector current identically vanishes for Majorana neutrinos.For non diagonal transitions, the Majorana condition strictly forbids the real (CP conserving) component of the vector interaction, leaving only a imaginary coupling. As a consequence, the observable difference in inclusive scattering cross-sections between Dirac and Majorana neutrinos is driven entirely by the FCNC CP-violating couplings. We apply these results to Coherent Elastic Neutrino-Nucleus Scattering (CEnuNS), showing that for spin-zero targets, the distinguishability of the neutrino's nature is determined by the CP structure of the new interaction.

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arXiv2017

Distinguishing Dirac and Majorana neutrinos with astrophysical fluxes

Massive neutrinos can have helicity $s_{\parallel}\neq -1$. Neutrino helicity changes when the neutrino interacts with an external magnetic field and it is possible that the left-handed neutrinos born inside the Sun or a supernova could leave their sources with a different helicity. Since Dirac and Majorana neutrinos have different cross sections in the scattering on electrons for different neutrino helicities, a change in the final neutrino helicity may generate a different number of events and spectra in terrestrial detectors when astrophysical neutrinos have travelled regions with strong magnetic fields. In this work, we show that looking for these effects in solar neutrinos, it could be possible to set bounds in the neutrino properties such as the neutrino magnetic moment. Furthermore, for neutrinos coming from a supernova, we show that even in the case of an extremely small neutrino magnetic moment, $\mu_\nu \sim 10^{-19}\mu_B$, there will be measurable differences in both the number of events and in the spectra of Majorana and Dirac neutrinos.

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