arXiv subjects

Yago Porto

Publications and source records attributed to Yago Porto.

11 recordsLinked to original sources

arXiv2026

Ruling Out Spiky WIMP Dark Matter using Indirect Searches

The dark matter (DM) density profile in the innermost region of the Galaxy remains an open question. In particular, while adiabatic growth of the supermassive black hole Sgr A$^\ast$ at the Galactic Center (GC) can induce a 'spike' in central DM density, the existence of such a spike is still under debate. Here we present new constraints on the spike slope $\gamma_{\rm sp}$ using conventional DM indirect detection searches. We first recast existing photon and neutrino line searches, which include the contribution from the GC region, into constraints on the thermally-averaged DM annihilation cross section $\langle\sigma v\rangle$ in the presence of a DM spike. We then derive new bounds on the spike profile for a generic Weakly Interacting Massive Particle (WIMP) DM scenario, where the thermal freeze-out mechanism fixes the annihilation cross-section at $\langle\sigma v\rangle\sim (2-3) \times 10^{-26}~{\rm cm}^3~{\rm s}^{-1}$. We find that, for DM annihilation to photons, existing \emph{Fermi}-LAT and MAGIC data place strong constraints on spike profiles at the GC over a broad range of WIMP DM masses, from 10 GeV to 100 TeV, for photon branching fractions down to $\sim 10^{-2}$, and remain sensitive to values as small as $\sim 10^{-4}$ in parts of the parameter space. For the neutrino channel, we use the recent IceCube data to constrain the existence of an extremely steep spike in the $\mathscr{O}(1-10)$~TeV DM mass range. Our analysis can be easily extended to other annihilation channels.

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arXiv2025

$N_{\textrm{eff}}$ Constraint on Pseudo-Dirac Neutrinos

After the electroweak symmetry breaking, we can write down two types of mass for the Standard Model neutrinos, Dirac or Majorana. It is often said that both types of mass cannot be distinguished in neutrino oscillation phenomena. This is in fact not true if neutrinos are pseudo-Dirac (strictly speaking still Majorana) where they mix almost maximally with sterile neutrinos to form pseudo-Dirac pairs. If this is indeed realized in Nature, what we observe experimentally as three mass eigenstates are actually three pairs of mass eigenstates with yet-to-be-measured new mass splitting among each pair. While the new mass squared splitting of the first and second mass eigenstates have stringent constraints from solar neutrino to be $|\delta m_{1,2}^2| \lesssim10^{-11}\,\textrm{eV}^{2}$, the one regarding the third mass eigenstate has a weaker constraint $|\delta m_3^2| \lesssim10^{-5}\,\textrm{eV}^{2}$. By keeping only one nonzero pseudo-Dirac mass squared splitting at a time, we derive an effective 3+1 description for the pseudo-Dirac scenario. Then we use the Cosmic Microwave Background (CMB) constraint on neutrino relativistic degrees of freedom $N_{\textrm{eff}}$ to derive a new constraint $|\delta m_3^2| < 2 \times 10^{-6}\,{\rm eV}^2$ and show that the future CMB-S4 and CMB-HD can improve this bound by an order of magnitude.

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arXiv2025

Expected flavor composition of supernova neutrinos

We revisit the flavor composition of neutrinos from core-collapse supernovae (SN), focusing on robust predictions that are insensitive to the poorly known dynamics of collective flavor conversion in the inner core. Assuming that the many different trajectories and microscopic histories of neutrinos lead to decoherence of the ensemble at the boundary between the region of collective effects and the Mikheyev-Smirnov-Wolfenstein (MSW) dominated layers, we show that standard matter effects alone strongly constrain the electron-flavor fraction at Earth. For normal mass ordering (NO) we obtain $f_{\nu_e}^{\rm NO}\lesssim 0.5$ at all times and energies, while for inverted ordering (IO), we predict $f_{\nu_e}^{\rm IO}\simeq 1/3$, i.e.\ near flavor equipartition. Shock-wave propagation through the high (H) MSW resonance drives the system toward equipartition also in NO. In this way our framework links simple assumptions about decoherence and standard matter effects to robust expectations for the flavor evolution inside core-collapse supernovae. This contribution summarizes the main results of arXiv:2403.14762.

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arXiv2025

Scalar non-standard neutrino interactions in Galactic supernovae

We analyze the prospects for studying scalar non-standard interactions (SNSI) using the neutrino burst from a Galactic supernova. SNSI modify the resonant flavor conversion and, correspondingly, the neutronization burst signal, and may be identifiable in future multi-tonne-scale experiments such as DUNE. We show that, in the presence of SNSI, neutrinos propagating out of the dense supernova environment acquire a density-squared-dependent contribution to their mass-squared differences, which in turn modifies the energy levels of the neutrino mass eigenstates. This phenomenon is not present in less dense environments like the Earth or the Sun. For a given mass ordering, supernova neutrinos can improve the sensitivity to SNSI parameters by up to four orders of magnitude compared to that achievable with solar or terrestrial neutrino sources.

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arXiv2025

Neutrino Theory in the Precision Era

This document summarises discussions on future directions in theoretical neutrino physics, which are the outcome of a neutrino theory workshop held at CERN in February 2025. The starting point is the realisation that neutrino physics offers unique opportunities to address some of the most fundamental questions in physics. This motivates a vigorous experimental programme which the theory community fully supports. \textbf{A strong effort in theoretical neutrino physics is paramount to optimally take advantage of upcoming neutrino experiments and to explore the synergies with other areas of particle, astroparticle, and nuclear physics, as well as cosmology.} Progress on the theory side has the potential to significantly boost the physics reach of experiments, as well as go well beyond their original scope. Strong collaboration between theory and experiment is essential in the precision era. To foster such collaboration, \textbf{we propose to establish a CERN Neutrino Physics Centre.} Taking inspiration from the highly successful LHC Physics Center at Fermilab, the CERN Neutrino Physics Centre would be the European hub of the neutrino community, covering experimental and theoretical activities.

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arXiv2025

Signatures of quasi-Dirac neutrinos in diffuse high-energy astrophysical neutrino data

Although the sources of astrophysical neutrinos are still unknown, they are believed to be produced by a population of sources in the distant universe. Measurements of the diffuse, all-sky astrophysical flux can thus be sensitive to flavor and energy-dependent propagation effects, such as very long baseline oscillations. These oscillations are present in certain neutrino mass models, such as when neutrinos are quasi-Dirac. Assuming generic models for the source flux, we find that these oscillations can still be resolved even when integrated over wide distributions in source redshift. We use two sets of IceCube all-sky flux measurements, made with muon and all-flavor neutrino samples, to set constraints at the $3\sigma$ level on quasi-Dirac mass-splittings between $(5 \times 10^{-19}, 8 \times 10^{-19})~\textrm{eV}^2$. We also consider systematic uncertainties on the source population and find that our results are robust under alternate spectral hypotheses or physical redshift distributions. Our analysis shows that spectral features in the all-sky neutrino measurements provide strong constraints on massive neutrino scenarios and are sensitive to uncharted parameter space.

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arXiv2024

Non-Standard Interactions of Supernova Neutrinos and Mass Ordering Ambiguity at DUNE

We show that non-standard neutrino interactions (NSI) can notably modify the pattern of resonant flavor conversion of neutrinos within supernovae and significantly impact the neutronization burst signal in forthcoming experiments such as the Deep Underground Neutrino Experiment (DUNE). The presence of NSI can invert the energy levels of neutrino matter eigenstates and even induce a new resonance in the inner parts close to the proto-neutron star. We demonstrate how DUNE can use these new configurations of energy levels to have sensitivity to NSIs down to $\mathcal{O}(0.1)$. We also elucidate how the effect may result in a puzzling confusion of normal and inverted mass orderings by highlighting the emergence or vanishing of the neutronization peak, which distinguishes between the two mass orderings. Potential implications are analyzed thoroughly.

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arXiv2024

Constraining the pseudo-Dirac nature of neutrinos using astrophysical neutrino flavor data

The three Standard Model neutrinos can have Majorana mass or strictly Dirac mass, but both scenarios are practically indistinguishable in neutrino oscillation experiments. If they are pseudo-Dirac, however, there will be new mass splittings among the pseudo-Dirac pairs, potentially leaving traces in neutrino oscillation phenomena. In this work, we use flavor ratios of astrophysical neutrinos to discriminate different possible mass spectra of pseudo-Dirac neutrinos. We show that it will be possible to impose robust bounds of order $\delta m^2_3 \lesssim 10^{-12}$ $\text{eV}^2$ on the new mass squared splitting involving the third pseudo-Dirac mass eigenstates (those with the least electron flavor composition) with the future experiment IceCube-Gen2. The derived sensitivity is robust because it only assumes an extragalactic origin for the astrophysical neutrinos and hierarchical pseudo-Dirac mass spectrum. In case the neutrino sources are known in the future, such bounds can potentially improve by up to five orders of magnitude, reaching $\delta m^2_3 \lesssim 10^{-17}$ $\text{eV}^2$.

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arXiv2024

Flavor composition of supernova neutrinos

Predicting the flavor composition of neutrinos from supernovae is a challenging task, primarily due to the high neutrino densities at their core. In such an environment, neutrino self-interactions give rise to collective effects that have dramatic yet poorly understood consequences for their flavor evolution. In this paper, however, we show that standard matter effects in the outer layers of supernovae can significantly constrain the flavor composition of the neutrino flux. We assume that, since a large number of neutrinos undergo different evolutions within the core, their state upon entering the MSW-dominated region is affected by decoherence. This assumption simplifies the problem and suggests that the fraction of neutrinos with electron flavor reaching Earth, denoted as $f_{\nu_e}$, is constrained to be less than $0.5$ for all energies throughout the emission phase in the case of normal mass ordering. In contrast, for inverted mass ordering, we anticipate neutrinos arriving in near flavor equipartition ($f_{\nu_e} \approx 1/3$). These predictions, and consequently their underlying assumptions, could be tested by future observations and may provide valuable insights into the properties of neutrino fluxes emerging from supernovae.

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arXiv2024

New Resonances of Supernova Neutrinos in Twisting Magnetic Fields

We investigate the effect of resonant spin conversion of the neutrinos induced by the geometrical phase in a twisting magnetic field. We find that the geometrical phase originating from the rotation of the transverse magnetic field along the neutrino trajectory can trigger a new resonant spin conversion of Dirac neutrinos inside the supernova, even if there were no such transitions in the fixed-direction field case. We have shown that even though resonant spin conversion is too weak to affect solar neutrinos, it could have a remarkable consequence on supernova neutronization bursts where very intense magnetic fields are quite likely. We demonstrate how the flavor composition at Earth can be used as a probe to establish the presence of non-negligible magnetic moments, potentially down to $10^{-15}~μ_B$ in upcoming neutrino experiments like the Deep Underground Neutrino Experiment (DUNE), and the Hyper-Kamiokande (HK). Possible implications are analyzed.

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arXiv2023

Flavor Matters, but Matter Flavors: Matter Effects on Flavor Composition of Astrophysical Neutrinos

We show that high-energy astrophysical neutrinos produced in the cores of heavily obscured active galactic nuclei (AGNs) can undergo strong matter effects, thus significantly influencing their source flavor ratios. In particular, matter effects can completely modify the standard interpretation of the flavor ratio measurements in terms of the physical processes occurring in the sources (e.g., $pp$ versus $p\gamma$, full pion-decay chain versus muon-damped pion decay). We contrast our results with the existing flavor ratio measurements at IceCube, as well as with projections for next-generation neutrino telescopes like IceCube-Gen2. Signatures of these matter effects in neutrino flavor composition would not only bring more evidence for neutrino production in central AGN regions, but would also be a powerful probe of heavily Compton-thick AGNs, which escape conventional observation in $X$-rays and other electromagnetic wavelengths.

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