27 August 2026

We investigate the connection between resonant leptogenesis and a primordial stochastic gravitational-wave background in a minimal two-right-handed-neutrino type-I seesaw with a real singlet scalar. The scalar sector admits a $\mathbb Z_2$-symmetric tree-level potential, while the tiny right-handed-neutrino coupling to the $\mathbb Z_2$-odd scalar generates a radiative vacuum-energy bias that causes the domain-wall network to annihilate. For quasi-degenerate heavy neutrinos, we describe the heavy-neutrino system with a density-matrix kinetic framework and use the ratio $r_q=\Delta M/\Gamma_{N_1}$ as an organizing variable for the separated, resonant and coherent regimes. The heavy-neutrino parameters that control the physical mass splitting also enter the radiatively generated domain-wall bias, providing a model-dependent link between the quantum-kinetic baryon asymmetry and the gravitational-wave peak frequency and amplitude. We emphasize that the gravitational- wave signal is not a direct measurement of an individual low-energy neutrino parameter; rather, it provides a model-dependent consistency relation among neutrino data, resonant leptogenesis, domain-wall annihilation and the stochastic gravitational-wave background.

Left--right symmetric theories with generalized parity restrict the bare QCD angle to a CP-conserving value and relate the physical strong-CP phase \(\bar\theta\) to a CP-odd parity-breaking parameter \(\eps\). We show that, in the Dirac-neutrino realization, imposing a sectorial reality condition on the Dirac lepton Yukawa matrices turns observable leptonic CP violation from an independent input into a branch-dependent prediction. Parity reconstructs the right-handed leptonic mixing matrix, whereas leptonic reality requires it to be rephasing-equivalent to the complex conjugate of the left-handed one. For generic three-generation Yukawas, compatibility is equivalent to the vanishing of a single Jarlskog-type CP-odd invariant. In the physical Dirac hierarchy, for fixed oscillation data, mass ordering, and discrete leptonic branch, compatibility determines the PMNS Jarlskog invariant as a function of the lightest neutrino mass and \(\eps\). We derive its leading analytic behavior and obtain the nonlinear compatibility branches numerically. In compressed mixed-sign Dirac-neutrino spectra, small signed mass sums can amplify a tiny parity deformation into order-one values of the normalized PMNS Jarlskog invariant, including maximal CP violation. The corresponding quark reconstruction independently provides a calculable, branch-dependent conversion between \(\eps\) and \(\bar\theta\). Together, the leptonic and quark relations define a family of correlations among leptonic CP violation, the absolute neutrino mass scale, and strong CP.

We study neutrino oscillations in an ultralight axion-like particle (ALP) dark-matter background using a bottom-up derivative interaction for active neutrinos. For couplings diagonal in the neutrino mass basis, the leading relative phase is fixed by the difference of the ALP field between production and detection. More generally, an unresolved background multiplies each interference term by the characteristic function of this endpoint field difference. For a single fixed-amplitude coherent mode with uniformly sampled phase, the factor is $J_0(A_{ij})$. In the slow-flight and small-dephasing regimes, this result and a Gaussian virialized-halo treatment agree at quadratic order and produce a leading $L^2E^0$ suppression. We identify the finite-exposure and coherence conditions under which the two statistical descriptions apply. As an application, we analytically map the energy-independent damping constraint derived from the first JUNO data onto the flavor benchmark $g_2=g_3$. For a local ALP density of $0.4\mathrm{GeV}/\mathrm{cm}^3$, the low-mass plateau gives $|\Delta g_{21}|=|\Delta g_{31}|\lesssim0.90\mathrm{GeV}^{-1}$. This number is a baseline-matched EFT recast of the reference damping analysis. No specific ultraviolet completion is assumed.

In this note, we describe the Gepner construction purely as orbifold (rather than a beta-prescription or orbifold-like process). This is done by distinguishing orbifolding by a chiral symmetry from that by a left-right diagonal symmetry, and also by exploiting an extra degree of freedom available in orbifolds of Type 0 SCFTs. We also describe by using the Arf theory how the extra freedom in Type 0 SCFT orbifolds in general (not just in the Gepner construction) should be implemented in higher genus amplitudes. This note also determines when a combinatorial data set of a Gepner construction has a mirror Gepner construction, and also provides two thinking frameworks to determine the SCFT vertex operators of the Gepner model SCFTs with phase ambiguity and branch cuts under control.

In this work, we revamp the democratic mixing matrix (DM) by adding a perturbation term such that the mixing angles derived from it are compatible with the NuFIT 6.1 and recent findings from the Jiangmen Underground Neutrino Observatory (JUNO). To do this, we have incorporated perturbation term in the elements of the mixing matrix such that it does not lose its unitarity. Thus, the democratic mixing matrix, once ruled out by the experimental evidences from T2K, Double Chooz, and Daya Bay, can be modified with rotational perturbation in the (1,2), (1,3), and (2,3) sectors and additional real parameters added in each element of DM. Finally, we analyze the allowed and disallowed textures in light of the JUNO findings.

We propose a novel approach to detecting low-energy electron antineutrinos based on the induced capture of orbital electrons by nuclei. This process is resonant, requiring the antineutrino energy to precisely match the energy difference between the final and initial atomic systems. For continuous-spectrum sources, the resonance conditions can be satisfied without fine-tuning, and the effective cross sections depend on the spectral intensity of the $\bar{\nu}_e$ flux at the resonance rather than on the neutrino energy itself. This opens the possibility of detecting neutrinos of never previously probed low energies. We identify a number of candidate nuclides that allow transitions to excited states of the daughter nuclei corresponding to resonant $\bar{\nu}_e$ energies below the inverse $\beta$ decay threshold of 1.8 MeV, and we consider a distinctive atomic-nuclear coincidence signature for background rejection. We discuss implications of the proposed method for detecting low-energy reactor neutrinos, geoneutrinos, and keV-scale thermal solar neutrinos. Applications to neutrino oscillation experiments and to reactor monitoring are also briefly discussed.

The NUCLEUS experiment aims to study coherent elastic neutrino-nucleus scattering (CE$\nu$NS) of reactor electron antineutrinos at the Chooz nuclear power plant in France. In this work, the cryogenic target-detector module for the NUCLEUS Technical Run was developed and commissioned at the Technical University of Munich. The module comprises four gram-scale CaWO$_4$ detectors, each equipped with two Transition Edge Sensors (TES), providing a total target mass of 6.96 g. We present the design, integration, detector characterization, and X-ray-based energy calibration of these detectors. Across six characterized detectors, a mean baseline resolution of $\overline{\sigma}_{\mathrm{BL}} = (2.79 \pm 0.60)\,\mathrm{eV}$ was achieved. The best-performing detector reached $\sigma_{\mathrm{BL}} = (2.16 \pm 0.02_{\mathrm{stat}})\,\mathrm{eV}$, surpassing the design goal by a factor of two and representing a state-of-the-art result for a cryogenic CaWO$_4$ detector. The target detector module was successfully operated simultaneously with the surrounding Cryogenic Outer Veto, which consists of six kg-scale Ge detectors for background discrimination, showing no measurable cross-talk. These results demonstrate the readiness of the target-detector system for the NUCLEUS Technical Run at Chooz and mark a key milestone in the development of cryogenic detectors for reactor-CE$\nu$NS measurements.

Neutrino interaction generators are central to precision oscillation analyses, but conventional implementations do not directly provide derivatives of their predictions with respect to physics parameters, leaving analyses to obtain this dependence through reweighting, finite differences or external response models. We present ADoNIS, a fully differentiable neutrino interaction event generator that makes event reweighting and its gradients directly available, propagating exact derivatives through the nuclear ground state, hard-scattering amplitudes and stochastic intranuclear cascade. Following the physics choices of ACHILLES, we demonstrate agreement with its predictions across neutrino, electron and hadron probes, showing that differentiability is achieved without loss of physical fidelity. We then show how the resulting Jacobian exposes which measurements and regions of phase space constrain each parameter and how different probes break degeneracies, providing a quantitative tool for fit design, model tuning, measurement design and experiment design. The same differentiable predictions can be used directly in frequentist and Bayesian inference and carried through detector response to reconstructed observables for unfolding, while also yielding computational gains. In sum, ADoNIS provides a practical recipe for constructing differentiable neutrino event generators, applicable beyond the particular physics models implemented here, and this paper demonstrates their use across a wide range of tasks relevant to both theory and experiment.

Neutrino oscillation phenomenology is usually communicated through two-dimensional projections (probability curves, oscillograms, and bi-probability plots), each of which flattens a function of many parameters (baseline, energy, matter density, mass ordering, and the CP-violating phase) onto a single static figure. We present NuGlass, an open-source, web-based application that renders six complementary, fully interactive 3D views of the same underlying three-flavor evolution: an oscillogram surface, a bi-probability trajectory extruded along energy, a Bloch-sphere projection of the quantum flavor state, a matter-eigenstate phasor decomposition of the oscillation amplitude, a flavor-composition tube along the propagation baseline, and a worldline view that plots the probabilities against L/E and makes the matter-induced breaking of the vacuum degeneracy visible. An oscillation channel switcher, experiment presets, and customizable animation controls are provided. NuGlass can be used both as a research exploration tool and as a public-engagement exhibit. The application runs entirely client-side and is deployed at https://czczc.github.io/nuglass/ .

We present a first application of sparse-autoencoder-based mechanistic interpretability to particle physics. Studying a neutrino foundation model pretrained on IceCube data and fine-tuned for direction reconstruction, we identify a validated atlas of physical concepts in the model representation, using a strict validation protocol consisting of held-out tests, matched nuisance controls, and replication across independent dictionary trainings. Causal interventions show that the direction head barely draws on this atlas. Motivated by this underused information, we train an uncertainty head on the same event-level representation to predict the model's angular reconstruction error. Unlike the direction head, it depends causally on quality and brightness features from the atlas. At $20\%$ selection efficiency, this interpretable estimator improves the median angular resolution from $20.2^\circ$ to $3.2^\circ$. These results suggest that mechanistic interpretability can reveal learned latent physics encoded within a model's internal representation and help design downstream tasks that exploit it.