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 .

United States

Vedran Brdar

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.

Carlos A. Argüelles

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

Germany

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

CERN

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

A series of experiments studying neutrinos from intense radioactive sources have reported a deficit in the measured event rate which, in combination, has reached a statistical significance of ∼ 5σ. In this paper, we explore avenues for explaining this anomaly, both within the Standard Model and beyond. First, we discuss possible biases in the predicted cross section for the detection reaction ν  e  + 71Ga → e  −  + 71Ge, which could arise from mismeasurement of the inverse process, 71Ge decay, or from the presence of as yet unknown low-lying excited states of 71Ga. The latter would imply that not all 71Ge decays go to the ground state of 71Ga, so the extraction of the ground state-to-ground state matrix element relevant for neutrino capture on gallium would be incorrect. Second, we scrutinize the measurement of the source intensity in gallium experiments, and we point out that a ∼ 2% error in the branching ratios for 51Cr decay would be enough to explain the anomaly. Third, we investigate the calibration of the radiochemical germanium extraction efficiency as a possible origin of anomaly. Finally, we outline several new explanations beyond the Standard Model, including scenarios with sterile neutrinos coupled to fuzzy dark matter or to dark energy, as well as a model with decaying sterile neutrinos. We critically assess the viability of these scenarios, and others that have been proposed, in a summary table.

Julia Gehrlein

Joachim Kopp

Towards resolving the gallium anomaly

We scrutinize the hypothesis that gauge singlet fermions—sterile neutrinos—interact with Standard Model particles through the transition magnetic moment portal. These interactions lead to the production of sterile neutrinos in supernovae followed by their decay into photons and active neutrinos which can be detected at <math><mi>γ</mi></math>-ray telescopes and neutrino detectors, respectively. We find that the nonobservation of active neutrinos and photons from sterile-neutrino decay associated to SN1987A yields the strongest constraints to date on magnetic-moment-coupled sterile neutrinos if their masses are inside a 0.1–100 MeV window. Assuming a near-future galactic supernova explosion, we estimate the sensitivity of several present and near-future experiments, including Fermi-LAT, e-ASTROGAM, DUNE, and Hyper-Kamiokande, to magnetic-moment-coupled sterile neutrinos. We also study the diffuse photon and neutrino fluxes produced in the decay of magnetic-moment coupled sterile neutrinos produced in all past supernova explosions and find that the absence of these decay daughters yields the strongest constraints to date for sterile neutrino masses inside a 1–100 keV window.

André de Gouvêa

Pedro A. N. Machado

Neutrino magnetic moment portal and supernovae: New constraints and multimessenger opportunities

In this work we demonstrate that a future accelerator-based neutrino experiment such as DUNE can greatly increase its sensitivity to a variety of new physics scenarios by operating in a mode where the proton beam impinges on a beam dump. We consider two new physics scenarios, namely light dark matter and axionlike particles and show that by utilizing a dump mode at a DUNE-like experiment, unexplored new regions of parameter space can be probed with an exposure of only 3 months with half of its expected initial beam power. Specifically, targetless configuration of future high intensity neutrino experiments will probe the parameter space for thermal relic dark matter as well as the QCD axion. The strength of such a configuration in the context of new physics searches stems from the fact that the neutrino flux is significantly reduced compared to that of the target, resulting in much smaller backgrounds from neutrino interactions. We have verified this in detail by explicitly computing neutrino fluxes which we make publicly available in order to facilitate further studies with a targetless configuration.

Bhaskar Dutta

Wooyoung Jang

Doojin Kim

Ian M. Shoemaker

Zahra Tabrizi

Adrian Thompson

Jaehoon Yu

Probing new physics at DUNE operating in a beam-dump mode

LHAASO collaboration detected photons with energy above 10 TeV from the most recent gamma-ray burst (GRB), GRB221009A. Given the redshift of this event, <math><mi>z</mi><mo>∼</mo><mn>0.15</mn></math>, photons of such energy are expected to interact with the diffuse extragalactic background light (EBL) well before reaching Earth. In this paper we provide a novel neutrino-related explanation of the most energetic 18 TeV event reported by LHAASO. We find that the minimal viable scenario involves both mixing and transition magnetic moment portal between light and sterile neutrinos. The production of sterile neutrinos occurs efficiently via mixing while the transition magnetic moment portal governs the decay rate in the parameter space where tree-level decays via mixing to non-photon final states are suppressed. Our explanation of this event, while being consistent with the terrestrial constraints, points to the non-standard cosmology.

Neutrino origin of LHAASO's 18 TeV GRB221009A photon

Several neutrino experiments have reported results that are potentially inconsistent with our current understanding of the lepton sector. A candidate solution to these so-called short-baseline anomalies is postulating the existence of new, eV-scale, mostly sterile neutrinos that mix with the active neutrinos. This hypothesis, however, is strongly disfavored once one considers all neutrino data, especially those that constrain the disappearance of muon and electron neutrinos at short baselines. Here, we show that if the sterile-active mixing parameters depend on the energy scales that characterize neutrino production and detection, then the sterile-neutrino hypothesis may provide a reasonable fit to all neutrino data. The reason for the improved fit is that the stringent disappearance constraints on the different elements of the extended neutrino mixing matrix are associated to production and detection energy scales that are different from those that characterize the anomalous appearance data at MiniBooNE. We show, via a concrete example, that secret interactions among the sterile neutrinos can lead to the results of interest.

K. S. Babu

Addressing the short-baseline neutrino anomalies with energy-dependent mixing parameters