Violations of classicality can be probed through measurements performed on a system at different times, as proposed by Leggett and Garg. Specifically, violations of Leggett-Garg inequalities suggest the presence of quantum effects in macroscopic systems. Long-baseline neutrino experiments provide some of the longest available propagation distances over which such tests can be performed. Previous studies of Leggett-Garg tests in the neutrino sector have largely focused on showing that the oscillation probabilities can violate classical bounds for certain parameter choices. In this work, we develop a more complete and data-driven framework that treats both the distributions representing the classical and quantum behavior, as well as the experimental uncertainties. We consider MINOS, T2K, NOvA, as well as the upcoming DUNE, and present the respective statistical significance for distinguishing quantum behavior from classical scenarios at these long-baseline neutrino experiments. Among them, we find that T2K yields the most significant violation of classicality, at the level of ∼ 14$\textit{σ}$, with NOvA and projections for DUNE also resulting in a significance of more than 5$\textit{σ}$.

United States

Murshed Alam

Vedran Brdar

Dibya Chattopadhyay

Exploring quantumness at long-baseline neutrino experiments

Neutrino oscillation parameters are subject to renormalization group (RG) evolution, just like all couplings and masses of Standard Model (SM) particles. Within the SM extended with three massive neutrinos, it is well known that RG running effects in the neutrino sector are small. However, the RG running of the elements of the leptonic mixing (PMNS) matrix below the electroweak symmetry breaking scale can be enhanced in the presence of light neutrinophilic new particles. In this work, using a particular low-scale neutrino mass model as an example, and by taking into account both atmospheric and astrophysical neutrino fluxes, we show that RG running of the PMNS matrix can lead to an increased number of high-energy tau neutrino events at IceCube. This excess manifests as an increased number of spatially displaced showers called “double bangs”. We find that the number of double bangs induced by new physics through RG effects can be comparable to that arising from SM interactions of astrophysical tau neutrinos.

Samiur R. Mir

Carlos A. Argüelles

K.S. Babu

Double bangs at IceCube as a window to the neutrino mass origin

The KM3NeT collaboration recently reported the observation of KM3-230213A, a neutrino event with an energy exceeding 100 PeV, more than an order of magnitude higher than the most energetic neutrino in IceCube’s catalog. Given its longer data-taking period and larger effective area relative to KM3NeT, IceCube should have observed events around that energy. This tension has recently been quantified to lie between <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>2</mn><mi>σ</mi></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>3.5</mn><mi>σ</mi></math>, depending on the neutrino source. A <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">O</mi><mo stretchy="false">(</mo><mn>100</mn><mo stretchy="false">)</mo><mtext> </mtext><mtext> </mtext><mi>PeV</mi></math> neutrino detected at KM3NeT has traversed approximately 147 km of rock and sea en route to the detector, whereas neutrinos arriving from the same location in the sky would have only traveled through about 14 km of ice before reaching IceCube. We use this difference in propagation distance to address the tension between KM3NeT and IceCube. Specifically, we consider a scenario in which the source emits sterile neutrinos that partially convert to active neutrinos through oscillations. We scrutinize two such realizations, one where a new physics matter potential induces a resonance in sterile-to-active transitions and another one where off-diagonal neutrino nonstandard interactions are employed. In both cases, sterile-to-active neutrino oscillations become relevant at length scales of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo>∼</mo><mn>100</mn><mtext> </mtext><mtext> </mtext><mi>km</mi></math>, resulting in increased active neutrino flux near the KM3NeT detector, alleviating the tension between KM3NeT and IceCube. Overall, we propose the exciting possibility that neutrino telescopes may have started detecting new physics.

Dibya S. Chattopadhyay

Does the 220 PeV Event at KM3NeT Point to New Physics?

We propose heavy decaying dark matter (DM) as a new probe of the cosmic neutrino background (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="normal">C</mi><mi>ν</mi><mi mathvariant="normal">B</mi></mrow></math>). Heavy DM, with mass <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo>≳</mo><msup><mn>10</mn><mn>9</mn></msup><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>, decaying into neutrinos can be a new source of ultrahigh-energy (UHE) neutrinos. Including this contribution along with the measured astrophysical and predicted cosmogenic neutrino fluxes, we study the scattering of UHE neutrinos with the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="normal">C</mi><mi>ν</mi><mi mathvariant="normal">B</mi></mrow></math> via standard weak interactions mediated by the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>Z</mi></math> boson. We solve the complete neutrino transport equation, taking into account both absorption and reinjection effects, to calculate the expected spectrum of UHE neutrino flux at future neutrino telescopes, such as the IceCube-Gen2 radio. We argue that such observations can be used to probe the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="normal">C</mi><mi>ν</mi><mi mathvariant="normal">B</mi></mrow></math> properties and, in particular, local <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="normal">C</mi><mi>ν</mi><mi mathvariant="normal">B</mi></mrow></math> clustering. We find that, depending on the absolute neutrino mass and the DM mass and lifetime, a local <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="normal">C</mi><mi>ν</mi><mi mathvariant="normal">B</mi></mrow></math> overdensity <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo>≳</mo><msup><mn>10</mn><mn>6</mn></msup></math> can be probed at the IceCube-Gen2 radio within ten years of data taking.

Writasree Maitra

Anna M. Suliga

Germany

P.S. Bhupal Dev

Dark-matter-enhanced probe of relic neutrino clustering

In this work, motivated by several beyond the Standard Model signal topologies, we perform detailed background mitigation analyses for the DUNE near detector. Specifically, we investigate <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi>e</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>e</mi></mrow><mrow><mo>−</mo></mrow></msup></mrow></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi>e</mi></mrow><mrow><mo>−</mo></mrow></msup><mi>γ</mi></mrow></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>γ</mi></math>, and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>γ</mi><mi>γ</mi></math> final states that may arise from long-lived particles, including light mediators, dark matter, heavy neutral leptons, and axionlike particles (ALPs), decaying or scattering inside the liquid argon detector. To this end, we employ both photophilic and leptophilic ALPs as phenomenological benchmarks. The aforementioned final states leave a hard electromagnetic signature with no hadronic activity above the detector energy thresholds. Nevertheless, such signatures are not immune to backgrounds from neutrino scattering in the detector, which are in the focus of our study. In order to model realistic experimental analyses, we take into account particle misidentification rates, cross-contamination effects, and detector responses. We calculate confidence limit projections for DUNE, thereby presenting realistic capabilities for constraining or discovering new physics manifested through electromagnetic showers.

Bhaskar Dutta

Wooyoung Jang

Doojin Kim

Ian M. Shoemaker

CERN

Zahra Tabrizi

Adrian Thompson

Jaehoon Yu

Finding BSM needles in electromagnetic haystacks at DUNE

The transition magnetic moment between active and sterile neutrinos is theoretically well-motivated scenario beyond the Standard Model, which can be probed in cosmology, astrophysics, and at terrestrial experiments. In this work, we focus on the latter by examining such an interaction at proposed lepton colliders. Specifically, in addition to revisiting LEP, we consider CEPC, FCC-ee, CLIC, and the muon collider, motivated by the potential realization of any of them. Within the effective field theory framework, we present parameter regions that can be probed, highlighting the dependence on the lepton flavor interacting with the sterile neutrino. By including several new processes with large sterile neutrino production cross sections at high-energy lepton colliders, we find that the expected sensitivity for the active-to-sterile neutrino transition magnetic moment can reach $\textit{d}$ ≃ $$ \mathcal{O}\left({10}^{-7}\right) $$ GeV .

China

Ying-Ying Li

Samiur Mir

Yi-Lin Wang

Collider prospects for the neutrino magnetic moment portal

Neutrino telescopes, including IceCube, can detect galactic supernova events by observing the collective rise in photomultiplier count rates with a subsecond time resolution. Leveraging precise timing, we demonstrate for the first time the ability of neutrino telescopes to explore new weakly coupled states emitted from supernovae and subsequently decaying to neutrinos. Our approach utilizes publicly available packages, asteria and snewpy, for simulating detector responses and parametrizing neutrino fluxes originating from the standard model and new physics. We present results for two beyond-the-standard model scenarios and introduce the tool developed for testing a diverse range of new physics models.

Belgium

Jeffrey Lazar

Supernovae Time Profiles as a Probe of New Physics at Neutrino Telescopes

We scrutinize the potential of upcoming ultranear reactor neutrino experiments to detect radiative corrections in the elastic neutrino-electron scattering channel, focusing on the JUNO-TAO and CLOUD detectors, which employ advanced scintillator detection technologies. Previous reactor experiments have already constrained the electron neutrino charge radius, which is a neutrino property associated with a certain subset of the total radiative corrections, and have achieved limits that are only about an order of magnitude away from the Standard Model prediction. Our study demonstrates that JUNO-TAO and CLOUD could discover the neutrino charge radius in the near future, considering the established treatment of the charge radius. However, we show that it is necessary to go beyond this standard treatment. By including the complete set of one-loop level radiative corrections, we find a partial cancellation with the charge radius effect, reducing the experimental sensitivity to this quantity. Nevertheless, JUNO-TAO and CLOUD still have the potential to achieve a <math><mn>5</mn><mi>σ</mi></math> discovery but over longer timescales within a reasonable operational time frame.

Brazil

Leonardo J. Ferreira Leite

George A. Parker

Xun-Jie Xu

Neutrino charge radius and additional one-loop radiative corrections at ultranear reactor experiments

In this Letter, we propose reactoscope, a novel experimental setup for axionlike particle (ALP) searches. Nuclear reactors produce a copious number of photons, a fraction of which could convert into ALPs via Primakoff process in the reactor core. The generated flux of ALPs leaves the nuclear power plant and its passage through a region with a strong magnetic field results in the efficient conversion to photons that can be detected. Such magnetic field is the key component of axion haloscope experiments. Adjacent nuclear reactor and axion haloscope experiments exist in Grenoble, France. There, the Institut Laue-Langevin research reactor is situated only <math><mrow><mo>∼</mo><mn>700</mn><mtext> </mtext><mtext> </mtext><mi>m</mi></mrow></math> from GrAHal, the axion haloscope platform designed to offer several volume and magnetic field (up to 43 T) configurations. We derive sensitivity projections for photophilic ALP searches with the institute and GrAHal, and also scrutinize analogous realizations, such as the one comprising the Axion Solar Telescope experiment at CERN and the Bugey nuclear power plant. The results that we obtain complement and extend the reach of existing laboratory experiments, e.g., the light-shining-through-walls experiment. While the derived sensitivities are not competitive when compared to the astrophysical limits, our analysis is free from the assumptions associated with those limits.

France

Italy

Fernando Arias-Aragón

Jérémie Quevillon

New Directions for Axionlike Particle Searches Combining Nuclear Reactors and Haloscopes

After being produced as electron neutrinos (<math><msub><mrow><mi>ν</mi></mrow><mrow><mi>e</mi></mrow></msub></math>), solar neutrinos partially change their flavor to <math><msub><mrow><mi>ν</mi></mrow><mrow><mi>μ</mi></mrow></msub></math> and <math><msub><mrow><mi>ν</mi></mrow><mrow><mi>τ</mi></mrow></msub></math> en route to Earth. Although the flavor ratio of the <math><msub><mrow><mi>ν</mi></mrow><mrow><mi>e</mi></mrow></msub></math> flux to the total flux has been well measured, the <math><msub><mrow><mi>ν</mi></mrow><mrow><mi>μ</mi></mrow></msub><mo>:</mo><msub><mrow><mi>ν</mi></mrow><mrow><mi>τ</mi></mrow></msub></math> composition has not yet been experimentally probed. In this work we investigate the potential of the next-generation experiments for measuring the <math><msub><mrow><mi>ν</mi></mrow><mrow><mi>μ</mi></mrow></msub><mo>:</mo><msub><mrow><mi>ν</mi></mrow><mrow><mi>τ</mi></mrow></msub></math> flavor ratio by utilizing flavor-dependent radiative corrections in the cross sections for <math><msub><mrow><mi>ν</mi></mrow><mrow><mi>μ</mi></mrow></msub></math> and <math><msub><mrow><mi>ν</mi></mrow><mrow><mi>τ</mi></mrow></msub></math> scattering. Since the transition probabilities of <math><msub><mrow><mi>ν</mi></mrow><mrow><mi>e</mi></mrow></msub></math> to <math><msub><mrow><mi>ν</mi></mrow><mrow><mi>μ</mi></mrow></msub></math> and <math><msub><mrow><mi>ν</mi></mrow><mrow><mi>τ</mi></mrow></msub></math> depend on the leptonic CP phase, we also investigate the sensitivity to the CP phase and show that a statistical significance of <math><mo>∼</mo><mn>1</mn><mi>σ</mi></math> could be reached through precision measurements of solar neutrino spectra.

Beyond tree level with solar neutrinos: Towards measuring the flavor composition and CP violation