Search Results (535)

In this work, we present a detailed comparison of the SuSAv2 (SuperScaling Approach version 2) and RDWIA (Relativistic Distorted-Wave Impulse Approximation) models with measurements of charged-current neutrino-induced single-pion production from different experiments (T2K, MINERvA and MiniBooNE), studying the differences between the two theoretical descriptions. The neutrino energy range in these experiments spans from hundreds of MeV to roughly 20 GeV, and the nuclear targets are mainly composed of ${}^{12}$C. The SuSAv2 model uses the single-nucleon inelastic structure functions from the ANL-Osaka DCC model, which allows for a separation of pion production channels, distinguishing between the ${\pi }^{+}$, ${\pi }^{-}$ and ${\pi }^0$ final states. In the RDWIA approach, the Hybrid model developed by the Ghent group is used for the description of the boson–pion–nucleon vertex. Full article

Motivated by the persistent short-baseline anomalies that hint at the possible existence of physics beyond the standard three-flavor paradigm, we study the phenomenology of light sterile neutrinos in the minimal (3 + 1) framework using two future experiments: the MuOn-decay MEdium-baseline NeuTrino beam experiment (MOMENT) and the Deep Underground Neutrino Experiment (DUNE). We place constraints on active–sterile mixing parameters, probe CP-violation discovery potential, and examine correlations between the standard Dirac CP phase and the additional CP phases arising from active–sterile mixing to quantify phase degeneracies. We present exclusion limits and demonstrate the crucial role of the near detector in improving sensitivities by one or two orders of magnitude compared to a configuration with only the far detector. We find that the presence of sterile neutrinos can reduce the CP-violation sensitivity in long-baseline neutrino oscillation experiments. For large sterile mass splittings, the rapid oscillations average out, leading to strong parameter degeneracies in DUNE. In contrast, MOMENT retains strong sensitivity to CP violation and efficiently disentangles the standard and sterile CP phases. Our results highlight the strong complementarity between DUNE and MOMENT and show that their combined capabilities provide a powerful test of the light sterile neutrino hypothesis in regions of the parameter space that remain weakly constrained by current data. Full article

We have used long observations of galaxy clusters obtained with the Rossi X-ray Timing Explorer to search for the 3.55 keV line from sterile neutrino decay. If a lepton-number asymmetry exists in one or more types of active neutrinos in the early Universe, sterile neutrinos can be produced via the Shi–Fuller mechanism. The data consist of 11 clusters observed for a total of 3.1 megaseconds using the Proportional Counter Array. A 2.5$\sigma$ excess of emission over a thermal model is found over the energy span of the 3.55 keV line in the combined spectra of the eight clusters that individually have an excess. These residuals are added to increase the signal to noise ratio of the excess, which is then modeled with a Gaussian to simulate the instrumental spectral response. We find a significant correlation (r = 0.76) for a line centered at 3.6 keV with a model flux of 3.07 × 10⁻⁵ ph cm⁻² s⁻¹. Mixing angle for detected clusters ranges from 2.0 to 21.6 × 10⁻¹⁰. The decay rate inferred from the line flux is strongly correlated (r = 0.87) with cluster temperature, which is due to hotter, more massive clusters having a larger amount of dark matter. Approximately half of the total flux comes from the Coma cluster. The mixing angle for Coma is calculated to be 6.2 × 10⁻¹⁰. We fit the Coma cluster spectrum with two different three-component models. The first includes a Gaussian fixed at 3.55 keV to model soft emission. The flux of the Gaussian is 5.6 × 10⁻¹² ph cm⁻² s⁻¹ or 1.3% of the total flux. The second three-component model uses a second thermal component to model soft emission. This model gives a temperature of 0–17 keV for the second thermal component and a lower temperature for the hot component. This indicates that the second thermal component is modeling high-energy residuals rather than low ones, where the Gaussian is. Though our line fluxes exceed most reported detections and upper limits, they do not overproduce the dark matter. We conclude that some fraction of the marginally detected excess could be attributed to the decay line since low-temperature thermal emission and systematics fail to model it completely. Full article

Pulsar wind nebulae (PWNe), formed when the wind originating from a rapidly rotating neutron star flows out into its surroundings, have now been observed across the electromagnetic spectrum from the radio to the PeV gamma-ray regime. For most of these sources, leptonic processes, where electrons interacting with background photon fields produce high-energy photons through inverse Compton scattering, are believed to be the origin of associated very-high-energy gamma-ray emission. As such, these objects cannot contribute significantly to the galactic hadronic cosmic ray flux at ∼TeV-PeV energies. However, in a handful of cases, the possibility for an energetically sub-dominant hadron population being accelerated and producing very to ultra-high energy gamma-rays through pion decay has not yet been comprehensively excluded. Such scenarios have received renewed attention in the light of recent results from the Large High Altitude Air Shower Observatory (LHAASO). In this review, we explore the theoretical background positing hadronic acceleration in galactic PWNe, considering cases where the hadrons escape from the pulsar surface and/or are accelerated in the wind, as well as potential ‘shock mixing’ scenarios. We also explore current and future possible constraints on a hadronic component to PWNe from observations. Full article

The 2x2 Demonstrator, a prototype for the Deep Underground Neutrino Experiment (DUNE) liquid argon (LAr) Near Detector, was exposed to the Neutrinos from the Main Injector (NuMI) neutrino beam at Fermi National Accelerator Laboratory (Fermilab). This detector is a prototype of a new modular design for a liquid argon time-projection chamber (LArTPC), comprising a two-by-two array of four modules, each further segmented into two optically isolated LArTPCs. The 2x2 Demonstrator features a number of pioneering technologies, including a low-profile resistive field shell to establish drift fields, native 3D ionization pixelated imaging, and a high-coverage dielectric light readout system. The 2.4-tonne active mass detector is flanked upstream and downstream by supplemental solid-scintillator tracking planes, repurposed from the MINERvA experiment, which track ionizing particles exiting the argon volume. The antineutrino beam data collected by the detector over a 4.5 day period in 2024 include over 30,000 neutrino interactions in the LAr active volume—the first neutrino interactions reported by a DUNE detector prototype. During its physics-quality run, the 2x2 Demonstrator operated at a nominal drift field of 500 V/cm and maintained good LAr purity, with a stable electron lifetime of approximately 1.25 ms. This paper describes the detector and supporting systems, summarizes the installation and commissioning, and presents the initial validation of collected NuMI beam and off-beam self-triggers. In addition, it highlights observed interactions in the detector volume, including candidate muon antineutrino events. Full article

We review the main neutrino emission mechanisms operating in dense quark matter under strong magnetic fields, with particular emphasis on conditions expected in the interiors of compact stars. We discuss the direct Urca and neutrino synchrotron processes in unpaired quark matter, incorporating the effects of Landau-level quantization. For the direct Urca process, the quantization of the electron energy spectrum plays a critical role, whereas quark quantization can often be neglected at sufficiently high baryon densities. The resulting field-dependent neutrino emissivity is anisotropic and exhibits an oscillatory behavior as a function of magnetic-field strength. We explore the implications of these effects for magnetar cooling and for possible anisotropic neutrino emission that could contribute to pulsar kicks. In addition, we review the $\nu \overline{\nu }$ synchrotron emission process, which, although subdominant, provides valuable insights into the interplay between magnetic fields and weak interactions in dense quark matter. Overall, our analysis highlights the nontrivial influence of strong magnetic fields on neutrino production in magnetized quark cores, with potential consequences for the thermal and dynamical evolution of compact stars. Full article

The announcement of the KM3-230213A neutrino is generating a flood of astrophysics studies, mostly investigating its origin. We here focus on aspects of this observation that could be relevant for research programs on quantum gravity and spacetime quantization. It is at least amusing that KM3-230213A most likely traveled billions of light-years, but its rest-frame existence only lasted less than 0.1 seconds and ended with it being hit by a nucleon of Planckian energy. In addition, and perhaps more significantly, KM3-230213A is a remarkable probe of the types of microscopic structure of spacetime conjectured in some quantum-spacetime scenarios, and according to one of these scenarios, there is a candidate source: the gamma-ray burst GRB090401B observed 14 years earlier. Full article

We perform a systematic analysis of the nuclear dependence of two-particle–two-hole meson-exchange current contributions to inclusive lepton-nucleus scattering within the relativistic mean-field framework. We present microscopic calculations of nuclear responses for a set of 17 nuclei, ranging from helium to uranium, using a model with different Fermi momenta for protons and neutrons. We propose a novel scaling prescription based on the two-particle phase space and key nuclear parameters. The resulting description is accurate over a wide range of nuclear targets, with typical deviations below 10%, and allows for a separate treatment of the different emission channels. In addition, a consistent benchmark against electron-scattering data is provided. The parametrization presented provides a practical framework for extending the responses to different nuclear targets in neutrino event generators. Full article

The Probe Of Extreme Multi-Messenger Astrophysics (POEMMA) is a proposed dual-satellite mission to observe Ultra-High-Energy Cosmic Rays (UHECRs), increase the statistics at the highest energies, and observe Very-High-Energy Neutrinos (VHENs) following multi-messenger alerts of astrophysical transient events, such as gamma-ray bursts and gravitational wave events, throughout the universe. POEMMA–Balloon with radio (PBR) is a small-scale version of the POEMMA design, adapted to be flown as a payload on one of NASA’s suborbital Super Pressure Balloons (SPBs) circling over the Southern Ocean for more than 20 days after a launch from Wanaka, New Zealand. The main science objectives of PBR are: (1) to observe UHECRs via the fluorescence technique from suborbital space; (2) to observe horizontal high-altitude air showers (HAHAs) with energies above the cosmic ray knee (E > 3PeV) using optical and radio detection for the first time; and (3) to follow astrophysical event alerts in the search of VHENs. The PBR instrument consists of a 1.1 m aperture Schmidt telescope similar to the POEMMA design, with two cameras on its focal surface: a Fluorescence Camera (FC) and a Cherenkov Camera (CC). In addition, PBR has a Radio Instrument (RI) optimized for detecting EASs (covering the 60–660 Mhz range). The FC observes UHECR-induced EASs in the ultraviolet (UV) spectrum using an array of 9216-pixel Multi-Anode Photo-Multiplier Tubes (MAPMTs) imaged every 1 $\mathsf{\mu }$s. The CC uses a 2048-pixel Silicon Photo-Multiplier (SiPM) imager to observe cosmic-ray-induced HAHAs and search for neutrino-induced upward-going EASs. The CC covers a spectral range of 320–900 nm, with an integration time of 10 ns. This contribution provides an overview of PBR instruments and their current status. Full article

This work describes the development of the Multi-channel Integrated Zone-sampling Analogue-memory based Readout (MIZAR) ASIC. This 64-channel chip was designed as part of NASA’s POEMMA Balloon with RADIO (PBR) mission, which aims to detect Ultra-High-Energy Cosmic Rays (UHECRs) and $\tau$ showers produced by the interaction of Cosmic Neutrinos (CNs) in the crust. The ASIC was implemented to read out a tile of 8 × 8 Silicon Photomultipliers (SiPMs) used to acquire the optical Cherenkov signals generated by Extensive Air Showers (EASs). A channel is partitioned into 256 cells where each one integrates an analogue memory, a Wilkinson Analog-to-Digital Converter (ADC) and a digital memory operating at the nominal sampling rate of 200 MS/s (with a 5 ns integration time). The signal is digitized on-chip, then the converted data is read out by an FPGA. The MIZAR also provides a 64-bit hitmap as a first-level trigger which can be elaborated by an external firmware. This ASIC can also be configured to further segment the channels into units of 32 or 64 cells each and the ADC resolution can be set to a range between 8 and 12 bits. The chip was designed in a commercial 65 nm CMOS technology node and it was submitted for production in December 2024. The ASICs were delivered in March 2025. Full article

Theories of flavor operate at various scales. Recently it has been pointed out that in the context of modular flavor symmetries, certain combinations of observables are highly constrained, or even uniquely fixed, by modular invariance and holomorphicity. We find that even in the absence of supersymmetry, these combinations are surprisingly immune against quantum corrections. Full article

The microscopic origin of the de Sitter entropy remains a central puzzle in quantum gravity that is related to the cosmological constant problem. Within the paradigm of $\mathcal{H}$olographic $\mathcal{N}$aturalness, we propose that this entropy is carried by a vast number of light, coherent degrees of freedom—called “hairons”—which emerge as the moduli of gravitational instantons on orbifolds. Starting from the Euclidean de Sitter instanton ($S^4$), we construct a new class of orbifold gravitational instantons, $S^4/{\mathbb{Z}}_N$, where N corresponds to the de Sitter entropy. We demonstrate that the dimension of the moduli space of these instantons scales linearly with N, and we identify these moduli with the hairon fields. A ${\mathbb{Z}}_N$ symmetry, derived from Wilson loops in the instanton background, ensures the distinguishability of these modes, leading to the correct entropy count. The hairons acquire a mass of the order of the Hubble scale and exhibit negligible mutual interactions, suggesting that the de Sitter vacuum is a coherent state, or Bose–Einstein condensate, of these fundamental excitations. Then, we present a novel framework which unifies neutrino mass generation with the cosmological constant through gravitational topology and holography. The small neutrino mass scale emerges naturally from first principles, without requiring new physics beyond the Standard Model and Gravity. The gravitational Chern–Simons structure and its anomaly with neutrinos force a topological Higgs mechanism, leading to neutrino condensation via $S^4/{\mathbb{Z}}_N$ gravitational instantons. The number of topological degrees of freedom $N\sim M_{\mathrm{P}}^2/\mathrm{\Lambda }\sim {10}^{120}$ provides both the holographic counting of the de Sitter entropy and a $1/N$information see-saw mechanism for neutrino masses. Our framework makes the following predictions: (i) a neutrino superfluid condensation forming Cooper pairs below meV energies, as a viable candidate for cold dark matter; (ii) a possible resolution of the strong CP problem through a QCD composite axion state; (iii) time-varying neutrino masses which track the evolution of dark energy; and (iv) several distinctive signatures in astroparticle physics, ultra-high-energy cosmic rays and high magnetic field experiments. Full article

The aim of this paper is to present a more complete analysis of the theoretical concepts and experimental aspects of the physics of photoproduction interactions involving nuclei. We thus determine the relative contributions of excited nucleon, $p\pi$, and $p\pi \pi$ resonances and $\rho$, $\eta$, $\omega$ and K production, as well as the subsequent decay channels leading to neutrino and $\gamma$-ray production. This treatment is based, in large part, on the most recent and extensive empirical data on particle photoproduction interactions off protons and He nuclei. It is shown that, in astrophysical sources with steep proton energy spectra, the $\Delta$(1232) resonance channel clearly dominates. However, a blend of $N^{*}$ resonances at ∼1400 GeV can contribute as much as 20% to the neutrino flux. It is further found that $\gamma$–He interactions produce approximately 10% of astrophysical pions, as compared with $\gamma p$ interactions. Full article

We discuss the problem of defining rest frames for mixed particles, showing that Quantum Reference Frames are necessary to incorporate mass superpositions. This approach reveals a strictly frame-dependent nature of entanglement. We investigate the phenomenological impact on neutrinos and neutral mesons, demonstrating that the transition to the rest frame generates entanglement. Full article

Recent analyses on the central compact object in the HESS J1731-347 supernova remnant reported not only surprising structural properties (mass M and radius R), but also an interesting thermal evolution. More precisely, it has been estimated that $M=0.{77}_{-0.17}^{+0.20}{M}_{\odot }$ and $R=10.4_{-0.78}^{+0.86}$ km (at the $1\sigma$ level), while a redshited surface temperature of ${153}_{-2}^{+4}$ keV at an age of 2–6 kyrs has been reported. In the present work, we conduct an in-depth investigation on the possible nature (hadronic, hybrid, quark) of this compact object by attempting to not only explain its mass and radius but also the corresponding estimations for its temperature and age. In the case of hybrid stars we also examine possible effects of the symmetry energy on the activation of different neutrino emitting process, and hence on the resulting cooling curves. We found that the reported temperature and age may be compatible to hadronic stellar configurations regardless of whether pairing effects are included. In the scenario of hybrid stars, we found that the strange quark matter core has to be in a superconducting state in order to reach an agreement with the observational constraints. In addition, the hadronic phase must be soft enough so that the direct Urca process is not activated. Furthermore, we have shown that the considered cooling constraints can be reconciled within the framework of strange stars. However, quark matter has to be in a superconducting state and the quark direct Urca process needs to be blocked. Full article