We use recent evidence of TeV neutrino events from the most significant astrophysical sources detected by IceCube – NGC 1068, TXS 0506+056, PKS 1424+240– to constrain the local and global overdensity of relic neutrinos and to explore potential new neutrino self-interactions. Assuming a relic neutrino overdensity, such high-energy neutrinos have travelled considerable distances through a sea of relic neutrinos and could have undergone scattering, altering their observed flux on Earth. Considering only Standard Model interactions, we constrain the relic overdensity to <math altimg='si1.svg'><mi>&#951;</mi><mo>&#8804;</mo><mn>2</mn><mo>&#215;</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>14</mn></mrow></msup></math> at the 90% confidence level, assuming the sum of neutrino masses saturates the cosmological bound, <math altimg='si2.svg'><msub><mrow><mo>&#8721;</mo></mrow><mrow><mi>i</mi></mrow></msub><msub><mrow><mi>m</mi></mrow><mrow><mi>i</mi></mrow></msub><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mn>0.13</mn></math> eV. We demonstrate that this limit improves for larger neutrino masses and study how it depends on the scale of the overdensity region. Considering new interactions between TeV-scale neutrinos and relic neutrinos, mediated by a light boson, we probe couplings of approximately <math altimg='si3.svg'><mi>g</mi><mo>&#8764;</mo><msup><mrow><mn>10</mn></mrow><mrow><mo linebreak='badbreak' linebreakstyle='after'>&#8722;</mo><mn>2</mn></mrow></msup></math> with current data for a boson mass around the MeV scale. We demonstrate that this limit improves with larger neutrino masses and the scale of the overdensity region.

United Kingdom

Jack Franklin

Ivan Martinez-Soler

Spain

Yuber F. Perez-Gonzalez

Jessica Turner

Probing the cosmic neutrino background and new physics with TeV-scale astrophysical neutrinos

In the $\textit{ν}$SM extended by adding an eV-scale sterile state, the (3 + 1) model, the sterile-active level crossing entails the MSW resonance, here referred as the sterile-active (SA) resonance. In this paper, we construct an effective theory of SA resonance which involves only the sterile-active mixing angles and ∆ $$ {m}_{41}^2 $$ , thanks to the given environment of high matter potential which freezes the $\textit{ν}$SM oscillations. We give our first attempt at an analytic treatment of the effective theory to illuminate the global picture of the SA resonance at a glance. We formulate a perturbative framework in which the structure of “texture zeros” of the $\textit{S}$ matrix in the flavor space and the suppression by the small parameters sin $\textit{θ}$ ($\textit{j}$ = 1$\textit{,}$ 2$\textit{,}$ 3) allows us to reveal the flavor–event-type hierarchy of the resonance-effect strength in the probabilities. We have shown that the cascade events dominantly comes from the three paths through $\textit{P}$($\textit{ν}$ → $\textit{ν}$ ), $\textit{P}$( $$ {\overline{\nu}}_e $$ → $$ {\overline{\nu}}_e $$ ), and $\textit{P}$( $$ {\overline{\nu}}_{\mu } $$ → $$ {\overline{\nu}}_{\tau } $$ ), and a three-component fit is suggested to disentangle the SA resonance generation mechanisms.

Mark Brettell

United States

Hisakazu Minakata

Sterile-active resonance: A global qualitative picture

We present an updated global analysis of neutrino oscillation data as of September 2024. The parameters $\textit{θ}$ , $\textit{θ}$ , $$ \Delta {m}_{21}^2 $$ , and $$ \mid \Delta {m}_{3\ell}^2\mid $$ ($\textit{ℓ}$ = 1$\textit{,}$ 2) are well-determined with relative precision at 3$\textit{σ}$ of about 13%, 8%, 15%, and 6%, respectively. The third mixing angle $\textit{θ}$ still suffers from the octant ambiguity, with no clear indication of whether it is larger or smaller than 45 . The determination of the leptonic CP phase $\textit{δ}$ depends on the neutrino mass ordering: for normal ordering the global fit is consistent with CP conservation within 1$\textit{σ}$, whereas for inverted ordering CP-violating values of $\textit{δ}$ around 270$\textit{°}$ are favored against CP conservation at more than 3$\textit{.}$6$\textit{σ}$. While the present data has in principle 2$\textit{.}$5–3$\textit{σ}$ sensitivity to the neutrino mass ordering, there are different tendencies in the global data that reduce the discrimination power: T2K and NOvA appearance data individually favor normal ordering, but they are more consistent with each other for inverted ordering. Conversely, the joint determination of $$ \mid \Delta {m}_{3\ell}^2\mid $$ from global disappearance data prefers normal ordering. Altogether, the global fit including long-baseline, reactor and IceCube atmospheric data results into an almost equally good fit for both orderings. Only when the $\textit{χ}$ table for atmospheric neutrino data from Super-Kamiokande is added to our $\textit{χ}$ , the global fit prefers normal ordering with ∆$\textit{χ}$ = 6$\textit{.}$1. We provide also updated ranges and correlations for the effective parameters sensitive to the absolute neutrino mass from $\textit{β}$-decay, neutrinoless double-beta decay, and cosmology.

Ivan Esteban

M. Gonzalez-Garcia

Michele Maltoni

João Pinheiro

Germany

Thomas Schwetz

NuFit-6.0: updated global analysis of three-flavor neutrino oscillations

In this letter, we study the potential of boosting the atmospheric neutrino experiments sensitivity to the neutrino mass ordering (NMO) sensitivity by incorporating inelasticity measurements. We show how this observable improves the sensitivity to the NMO and the precision of other neutrino oscillation parameters relevant to atmospheric neutrinos, specifically in the IceCube-Upgrade and KM3NeT-ORCA detectors. Our results indicate that an oscillation analysis of atmospheric neutrinos, including inelasticity information, has the potential to enhance the ordering discrimination by several units of <math><msup><mi>χ</mi><mn>2</mn></msup></math> in the assumed scenario of five and three years of running of IceCube-Upgrade and KM3NeT-ORCA detectors, respectively.

Santiago Giner Olavarrieta

Miaochen Jin

Carlos A. Argüelles

Pablo Fernández

Boosting neutrino mass ordering sensitivity with inelasticity for atmospheric neutrino oscillation measurement

Recently, the ANITA collaboration announced the detection of new, unsettling upgoing Ultra-High-Energy (UHE) events. Understanding their origin is pressing to ensure success of the incoming UHE neutrino program. In this work, we study their internal consistency and the implications of the lack of similar events in IceCube. We introduce a generic, simple parametrization to study the compatibility between these two observatories in Standard Model-like and Beyond Standard Model scenarios: an incoming flux of particles that interact with Earth nucleons with cross section σ, producing particle showers along with long-lived particles that decay with lifetime τ and generate a shower that explains ANITA observations. We find that the ANITA angular distribution imposes significant constraints, and when including null observations from IceCube only τ ~ 10 −3–10 −2 s and σ ~ 10 −33– 10 −32 cm2 can explain the data. This hypothesis is testable with future IceCube data. Finally, we discuss a specific model that can realize this scenario. Our analysis highlights the importance of simultaneous observations by high-energy optical neutrino telescopes and new UHE radio detectors to uncover cosmogenic neutrinos or discover new physics.

Toni Bertólez-Martínez

Carlos Argüelles

Jacobo Lopez-Pavon

Jordi Salvado

IceCube and the origin of ANITA-IV events

The relic neutrinos from old supernova explosions are among the most ancient neutrino fluxes within experimental reach. Thus, the diffuse supernova neutrino background (DSNB) could teach us if neutrino masses were different in the past (redshifts <math><mi>z</mi><mo>≲</mo><mn>5</mn></math>). Oscillations inside the supernova depend strongly on the neutrino mass-squared differences and the values of the mixing angles, rendering the DSNB energy spectrum sensitive to variations of these parameters. Considering a purely phenomenological parametrization of the neutrino masses as a function of redshift, we compute the expected local DSNB spectrum here on Earth. Given the current knowledge of neutrino oscillation parameters, especially the fact that <math><mo>|</mo><msub><mi>U</mi><mrow><mi>e</mi><mn>3</mn></mrow></msub><msup><mo>|</mo><mn>2</mn></msup></math> is small, we find that the <math><msub><mi>ν</mi><mi>e</mi></msub></math> spectrum could be significantly different from standard expectations if neutrinos were effectively massless at <math><mi>z</mi><mo>≳</mo><mn>1</mn></math> as long as the neutrino mass ordering is normal. On the other hand, the <math><msub><mover><mi>ν</mi><mo>¯</mo></mover><mi>e</mi></msub></math> flux is not expected to be significantly impacted. Hence, a measurement of both the neutrino and antineutrino components of the DSNB should allow one to test the possibility of recent neutrino mass generation.

André de Gouvêa

Manibrata Sen

Diffuse supernova neutrino background as a probe of late-time neutrino mass generation

The DARWIN collaboration recently argued that DARWIN (dark matter wimp search with liquid xenon) can collect, via neutrino-electron scattering, a large, useful sample of solar <math><mrow><mi>p</mi><mi>p</mi></mrow></math>-neutrinos, and measure their survival probability with subpercent precision. We explore the physics potential of such a sample in more detail. We estimate that, with 300 ton-years of data, DARWIN can also measure, with the help of current solar neutrino data, the value of <math><mrow><msup><mrow><mi>sin</mi></mrow><mrow><mn>2</mn></mrow></msup><msub><mrow><mi>θ</mi></mrow><mrow><mn>13</mn></mrow></msub></mrow></math>, with the potential to exclude <math><mrow><msup><mrow><mi>sin</mi></mrow><mrow><mn>2</mn></mrow></msup><msub><mrow><mi>θ</mi></mrow><mrow><mn>13</mn></mrow></msub><mo>=</mo><mn>0</mn></mrow></math> close to the three-sigma level. We explore in some detail how well DARWIN can constrain the existence of a new neutrino mass-eigenstate <math><msub><mi>ν</mi><mn>4</mn></msub></math> that is quasimass-degenerate with <math><msub><mi>ν</mi><mn>1</mn></msub></math> and find that DARWIN’s sensitivity supersedes that of all current and near-future searches for new, very light neutrinos. In particular, DARWIN can test the hypothesis that <math><msub><mi>ν</mi><mn>1</mn></msub></math> is a pseudo-Dirac fermion as long as the induced mass-squared difference is larger than <math><mrow><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>13</mn></mrow></msup><mtext> </mtext><mtext> </mtext><msup><mrow><mi>eV</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></math>, one order of magnitude more sensitive than existing constraints. Throughout, we allowed for the hypotheses that DARWIN is filled with natural xenon or <math><mrow><mmultiscripts><mrow><mi>Xe</mi></mrow><mprescripts></mprescripts><none></none><mrow><mn>136</mn></mrow></mmultiscripts></mrow></math>-depleted xenon.

Emma McGinness

<math><mrow><mi>p</mi><mi>p</mi></mrow></math> solar neutrinos at DARWIN

In this paper we show that the DUNE experiment can measure the Earth’s density profile by analyzing atmospheric neutrino oscillations. The crucial feature that enables such measurement is the detailed event reconstruction capability of liquid argon time projection chambers. This allows for studying the sub-GeV atmospheric neutrino component, which bears a rich oscillation phenomenology, strongly dependent on the matter potential sourced by the Earth. We provide a pedagogical discussion of the MSW and parametric resonances and their role in measuring the core and mantle densities. By performing a detailed simulation, accounting for particle reconstruction at DUNE, nuclear physics effects relevant to neutrino-argon interactions and several uncertainties on the atmospheric neutrino flux, we manage to obtain a robust estimate of DUNE’s sensitivity to the Earth matter profile. We find that DUNE can measure the total mass of the Earth at 9.3% precision with an exposure of 400 kton-year. By accounting for previous measurements of the total mass and moment of inertia of the Earth, the core, lower mantle and upper mantle densities can be determined with 9%, 14% and 22% precision, respectively, for the same exposure. Finally, for a low exposure run of 60 kton-year, which would correspond to two far detectors running for three years, we have found that the core density could be measured by DUNE at ∼ 30% precision.

Kevin Kelly

Pedro Machado

Puerto Rico

Yuber Perez-Gonzalez

DUNE atmospheric neutrinos: Earth tomography

Ever since the discovery of neutrinos, we have wondered if neutrinos are their own antiparticles. One remarkable possibility is that neutrinos have a pseudo-Dirac nature, predicting a tiny mass difference between active and sterile states. We analyze the neutrino data from SN1987A in the light of active-sterile oscillations and find a mild preference (<math><mi>Δ</mi><msup><mi>χ</mi><mn>2</mn></msup><mo>≈</mo><mn>3</mn></math>) for <math><mi>δ</mi><msup><mi>m</mi><mn>2</mn></msup><mo>=</mo><mn>6.31</mn><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>20</mn></mrow></msup><mtext> </mtext><mtext> </mtext><msup><mrow><mi>eV</mi></mrow><mn>2</mn></msup></math>. Notably, the same data is able to exclude <math><mi>δ</mi><msup><mi>m</mi><mn>2</mn></msup><mo>∼</mo><mo>[</mo><mn>2.55</mn><mo>,</mo><mn>3.01</mn><mo>]</mo><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>20</mn></mrow></msup><mtext> </mtext><mtext> </mtext><msup><mrow><mi>eV</mi></mrow><mn>2</mn></msup></math> with <math><mi>Δ</mi><msup><mi>χ</mi><mn>2</mn></msup><mo>&gt;</mo><mn>9</mn></math>, the tiniest mass differences constrained so far. We further consider the next-generation of experiments and demonstrate their sensitivity exploring the nature of the neutrino mass.

Signs of pseudo-Dirac neutrinos in SN1987A data

A variety of new physics scenarios allows for neutrinos to up-scatter into a heavy neutral lepton state. For a range of couplings and neutrino energies, the heavy neutrino may travel some distance before decaying to visible final states. When both the up-scattering and decay occur within the detector volume, these “double bang” events produce distinctive phenomenology with very low background. In this work, we first consider the current sensitivity at Super-Kamiokande via the atmospheric neutrino flux, and find current data may already provide new constraints. We then examine projected future sensitivity at DUNE and Hyper-Kamiokande, including both atmospheric and beam flux contributions to double-bang signals.

Canada

M. Atkinson

Pilar Coloma

Noemi Rocco

Ian Shoemaker

Heavy neutrino searches through double-bang events at Super-Kamiokande, DUNE, and Hyper-Kamiokande