Observation of a neutrino burst from the supernova SN1987A

Emission lines due to ionizing radiation from a compact object in the remnant of Supernova 1987A

The nearby Supernova 1987A was accompanied by a burst of neutrino emission, which indicates that a compact object (a neutron star or black hole) was formed in the explosion. There has been no direct observation of this compact object. In this work, we observe the supernova remnant with JWST spectroscopy, finding narrow infrared emission lines of argon and sulfur. The line emission is spatially unresolved and blueshifted in velocity relative to the supernova rest frame. We interpret the lines as gas illuminated by a source of ionizing photons located close to the center of the expanding ejecta. Photoionization models show that the line ratios are consistent with ionization by a cooling neutron star or a pulsar wind nebula. The velocity shift could be evidence for a neutron star natal kick.

Detecting High-Energy Neutrinos from Galactic Supernovae with ATLAS

We show that ATLAS, a collider detector, can measure the flux of high-energy supernova neutrinos, which can be produced from days to months after the explosion. Using Monte Carlo simulations for predicted fluxes, we find at most O(0.1-1) starting events and O(10-100) throughgoing events from a supernova 10 kpc away. Possible Galactic supernovae from Betelgeuse and Eta Carinae are further analyzed as demonstrative examples. We argue that, even with limited statistics, ATLAS has the ability to discriminate among flavors and between neutrinos and antineutrinos, making it a unique neutrino observatory so far unmatched in this capability.

Physical mechanism of core-collapse supernovae that neutrinos drive

The current understanding of the mechanism of core-collapse supernovae (CCSNe), one of the most energetic events in the universe associated with the death of massive stars and the main formation channel of compact objects such as neutron stars and black holes, is reviewed for broad readers from different disciplines of science who may not be familiar with the object. Therefore, we emphasize the physical aspects than the results of individual model simulations, although large-scale high-fidelity simulations have played the most important roles in the progress we have witnessed in the past few decades. It is now believed that neutrinos are the most important agent in producing the commonest type of CCSNe. The so-called neutrino-heating mechanism will be the focus of this review and its crucial ingredients in micro- and macrophysics and in numerics will be explained one by one. We will also try to elucidate the remaining issues.

Toward Powerful Probes of Neutrino Self-Interactions in Supernovae

Neutrinos remain mysterious. As an example, enhanced self-interactions (νSI), which would have broad implications, are allowed. At the high neutrino densities within core-collapse supernovae, νSI should be important, but robust observables have been lacking. We show that νSI make neutrinos form a tightly coupled fluid that expands under relativistic hydrodynamics. The outflow becomes either a burst or a steady-state wind; which occurs here is uncertain. Though the diffusive environment where neutrinos are produced may make a wind more likely, further work is needed to determine when each case is realized. In the burst-outflow case, νSI increase the duration of the neutrino signal, and even a simple analysis of SN 1987A data has powerful sensitivity. For the wind-outflow case, we outline several promising ideas that may lead to new observables. Combined, these results are important steps toward solving the 35-year-old puzzle of how νSI affect supernovae.

Anomalous cyclic in the neutrino oscillations

Neutrino physics is one of the most important topics in particle physics and cosmology. As it is known, neutrinos are weakly interacting fundamental particles with chargeless and very small masses. One of the most characteristic features of the neutrino that make a difference from other elementary particles is that it oscillates between the mass and flavour eigenstates. Due to these oscillations, neutrinos change from one flavour to another. So far in theory the possible effects of deformed space-time effects on oscillation have not been considered. In this study, we show for the first time that a deformed space-time metric will lead to fractional dynamics between mass and flavour changes and therefore cause a phase shift in the oscillation period. We also shortly discuss the possible relation between anomalous cyclic and relic neutrinos. The modification in the oscillation probabilities due to the studied effect in this work could be seen using relic neutrinos.

First Direct Observation of Collider Neutrinos with FASER at the LHC

We report the first direct observation of neutrino interactions at a particle collider experiment. Neutrino candidate events are identified in a 13.6 TeV center-of-mass energy pp collision dataset of 35.4  fb^{-1} using the active electronic components of the FASER detector at the Large Hadron Collider. The candidates are required to have a track propagating through the entire length of the FASER detector and be consistent with a muon neutrino charged-current interaction. We infer 153_{-13}^{+12} neutrino interactions with a significance of 16 standard deviations above the background-only hypothesis. These events are consistent with the characteristics expected from neutrino interactions in terms of secondary particle production and spatial distribution, and they imply the observation of both neutrinos and anti-neutrinos with an incident neutrino energy of significantly above 200 GeV.

Strong Supernova 1987A Constraints on Bosons Decaying to Neutrinos

Majoron-like bosons would emerge from a supernova (SN) core by neutrino coalescence of the form νν→ϕ and ν[over ¯]ν[over ¯]→ϕ with 100-MeV-range energies. Subsequent decays to (anti)neutrinos of all flavors provide a flux component with energies much larger than the usual flux from the "neutrino sphere." The absence of 100-MeV-range events in the Kamiokande-II and Irvine-Michigan-Brookhaven signal of SN 1987A implies that less than 1% of the total energy was thus emitted and provides the strongest constraint on the Majoron-neutrino coupling of g≲10^{-9}  MeV/m_{ϕ} for 100  eV≲m_{ϕ}≲100  MeV. It is straightforward to extend our new argument to other hypothetical feebly interacting particles.

Galactic neutrinos in the Milky Way

A source of neutrinos may lie within the midplane of the Galaxy.

Characterization of a kg-scale archaeological lead-based PbWO4 cryogenic detector for the RES-NOVA experiment

Core-collapse Supernovae (SNe) are one of the most energetic events in the Universe, during which almost all the star's binding energy is released in the form of neutrinos. These particles are direct probes of the processes occurring in the stellar core and provide unique insights into the gravitational collapse. RES-NOVA will revolutionize how we detect neutrinos from astrophysical sources, by deploying the first ton-scale array of cryogenic detectors made from archaeological lead. Pb offers the highest neutrino interaction cross-section via coherent elastic neutrino-nucleus scattering (CEνNS). Such process will enable RES-NOVA to be equally sensitive to all neutrino flavours. For the first time, we propose the use archaeological Pb as sensitive target material in order to achieve an ultra-low background level in the region of interest (O(1 keV)). All these features make possible the deployment of the first cm-scale neutrino telescope for the investigation of astrophysical sources. In this contribution, we will characterize the radiopurity level and the performance of a small-scale proof-of-principle detector of RES-NOVA, consisting in a PbWO₄ crystal made from archaeological-Pb operated as cryogenic detector.

Searching for Afterglow: Light Dark Matter Boosted by Supernova Neutrinos

A novel analysis is performed, incorporating time-of-flight (TOF) information to study the interactions of dark matter (DM) with standard model particles. After supernova (SN) explosions, DM with mass m_{χ}≲O(MeV) in the halo can be boosted by SN neutrinos (SNν) to relativistic speed. The SNν boosted DM (BDM) arrives on Earth with TOF which depends only on m_{χ} and is independent of the cross section. These BDMs can interact with detector targets in low-background experiments and manifest as afterglow events after the arrival of SNν. The characteristic TOF spectra of the BDM events can lead to large background suppression and unique determination of m_{χ}. New cross section constraints on sqrt[σ_{χe}σ_{χν}] are derived from SN1987a in the Large Magellanic Cloud with data from the Kamiokande and Super-Kamiokande experiments. Potential sensitivities for the next galactic SN with Hyper-Kamiokande are projected. This analysis extends the existing bounds on sqrt[σ_{χe}σ_{χν}] over a broad range of r_{χ}=σ_{χν}/σ_{χe}. In particular, the improvement is by 1-3 orders of magnitude for m_{χ}<O(100  keV) for σ_{χe}∼σ_{χν}. Prospects of exploiting TOF information in other astrophysical systems to probe exotic physics with other DM candidates are discussed.

Diffuse neutrino background from past core collapse supernovae

Core collapse supernovae are among the most powerful explosions in the Universe, which emit thermal neutrinos that carry away most of the gravitational binding energy released. These neutrinos produce a diffuse supernova neutrino background (DSNB), which is one of the largest energy budgets among all radiation backgrounds. Detecting the DSNB is an important goal of modern high-energy astrophysics and particle physics, which provides valuable insights into core collapse modeling, neutrino physics, and cosmic supernova rate history. In this review, the key ingredients of DSNB calculation and what can be learned from future detections, including black hole formation and non-standard neutrino interactions are discussed. Moreover, an overview of the latest updates in neutrino experiments, which could lead to the detection of the DSNB in the next decade, is provided. With the promise of this breakthrough discovery on the horizon, the study of DSNB has great potential to further our understanding of the Universe.

Absolute ν Mass Measurement with the DUNE Experiment

Time of flight delay in the supernova neutrino signal offers a unique tool to set model-independent constraints on the absolute neutrino mass. The presence of a sharp time structure during a first emission phase, the so-called neutronization burst in the electron neutrino flavor time distribution, makes this channel a very powerful one. Large liquid argon underground detectors will provide precision measurements of the time dependence of the electron neutrino fluxes. We derive here a new ν mass sensitivity attainable at the future DUNE far detector from a future supernova collapse in our galactic neighborhood, finding a sub-eV reach under favorable scenarios. These values are competitive with those expected for laboratory direct neutrino mass searches.

Minimal Realization of Light Thermal Dark Matter

We propose a minimal UV-complete model for kinematically forbidden dark matter (DM) leading to a sub-GeV thermal relic. Our crucial realization is that the two-Higgs-doublet model can provide a light mediator through which the DM can annihilate into standard model leptons, avoiding indirect detection constraints. The DM mass is predicted to be very close to the mass of the leptons, which can potentially be identified from DM annihilation into gamma rays. Because of the sizable couplings to muons required to reproduce the DM relic abundance, this framework naturally favors a resolution to the (g-2)_{μ} anomaly. Furthermore, by embedding this setup to the Zee model, we show that the phenomenon of neutrino oscillations is inherently connected to the observed relic abundance of DM. All new physics involved in our framework lies at or below the electroweak scale, making it testable at upcoming colliders, beam-dump experiments, and future sub-GeV gamma-ray telescopes.

A Multidimensional Multicomponent Gas Dynamic with the Neutrino Transfer in Gravitational Collapse

The self-consistent problem of gravitational collapse is solved using 2D gas dynamics with taking into account the neutrino transfer in the flux-limited diffusion approximation. Neutrino are described by spectral energy density, and weak interaction includes a simplified physical model of neutrino interactions with nucleons. I investigate convection on the stage of the collapse and then in the center of the core, where the unstable entropy profile was probably formed. It is shown that convection has large scale. Convection appears only in the semitransparent region near the neutrinosphere due to non-equilibrium nonreversible neutronization. Convection increases the energy of emitted neutrino up to 15÷18 MeV. The obtained neutrino spectrum is important for the registration of low-energy neutrinos from a supernova.

Maximum Likelihood Reconstruction of Water Cherenkov Events With Deep Generative Neural Networks

Large water Cherenkov detectors have shaped our current knowledge of neutrino physics and nucleon decay, and will continue to do so in the foreseeable future. These highly capable detectors allow for directional and topological, as well as calorimetric information to be extracted from signals on their photosensors. The current state-of-the-art approach to water Cherenkov reconstruction relies on maximum-likelihood estimation, with several simplifying assumptions employed to make the problem tractable. In this paper, we describe neural networks that produce probability density functions for the signals at each photosensor, given a set of inputs that characterizes a particle in the detector. The neural networks we propose allow for likelihood-based approaches to event reconstruction with significantly fewer assumptions compared to traditional methods, and are thus expected to improve on the current performance of water Cherenkov detectors.

Neutrino Dynamics in a Quantum-Corrected Schwarzschild Spacetime

We study neutrino propagation in a curved spacetime background described by the Schwarzschild solution with the addition of quantum corrections evaluated in the framework of perturbative quantum gravity at lowest order. In particular, we investigate neutrino oscillations and decoherence within the Gaussian wave packet description, finding that quantum gravity corrections significantly affect the intrinsic features of mixed particles and induce potentially measurable physical effects.

Searches for Violation of CPT Symmetry and Lorentz Invariance with Astrophysical Neutrinos

Neutrinos are a powerful tool for searching physics beyond the standard model of elementary particles. In this review, we present the status of the research on charge-parity-time (CPT) symmetry and Lorentz invariance violations using neutrinos emitted from the collapse of stars such as supernovae and other astrophysical environments, such as gamma-ray bursts. Particularly, supernova neutrino fluxes may provide precious information because all neutrino and antineutrino flavors are emitted during a burst of tens of seconds. Models of quantum gravity may allow the violation of Lorentz invariance and possibly of CPT symmetry. Violation of Lorentz invariance may cause a modification of the dispersion relation and, therefore, in the neutrino group velocity as well in the neutrino wave packet. These changes can affect the arrival time signal registered in astrophysical neutrino detectors. Direction or time-dependent oscillation probabilities and anisotropy of the neutrino velocity are manifestations of the same kind of new physics. CPT violation, on the other hand, may be responsible for different oscillation patterns for neutrino and antineutrino and unconventional energy dependency of the oscillation phase or of the mixing angles. Future perspectives for possible CPT and Lorentz violating systems are also presented.

Digging into Axion Physics with (Baby)IAXO

Dark matter searches have been ongoing for three decades; the lack of a positive discovery of the main candidate, the WIMP, after dedicated efforts, has put axions and axion-like particles in the spotlight. The three main techniques employed to search for them complement each other well in covering a wide range in the parameter space defined by the axion decay constant and the axion mass. The International AXion Observatory (IAXO) is an international collaboration planning to build the fourth generation axion helioscope, with an unparalleled expected sensitivity and discovery potential. The distinguishing characteristic of IAXO is that it will feature a magnet that is designed to maximise the relevant parameters in sensitivity and which will be equipped with X-ray focusing devices and detectors that have been developed for axion physics. In this paper, we review aspects that motivate IAXO and its prototype, BabyIAXO, in the axion, and ALPs landscape. As part of this Special Issue, some emphasis is given on Spanish participation in the project, of which CAPA (Centro de Astropartículas y Física de Altas Energías of the Universidad de Zaragoza) is a strong promoter.

On the Time Distribution of Supernova Antineutrino Flux

Neutrino leptonic flavor symmetry violation is the only evidence for physics beyond the standard model. Much of what we have learned on these particles is derived from the study of their natural sources, such as the Sun or core-collapse supernovae. Neutrino emission from supernovae is particularly interesting and leptonic flavor transformations in supernova neutrinos have attracted a lot of theoretical attention. Unfortunately, the emission of core-collapse supernovae is not fully understood: thus, an inescapable preliminary step to progress is to improve on that, and future neutrino observations can help. One pressing and answerable question concerns the time distribution of the supernova anti-neutrino events. We propose a class of models of the time distribution that describe emission curves similar to those theoretically expected and consistent with available observations from the data of supernova SN1987A. They have the advantages of being motivated on physical bases and easy to interpret; they are flexible and adaptable to the results of the observations from a future galactic supernova. Important general characteristics of these models are the presence of an initial ramp and that a significant portion of the signal is in the first second of the emission.

Advanced Virgo: Status of the Detector, Latest Results and Future Prospects

The Virgo detector, based at the EGO (European Gravitational Observatory) and located in Cascina (Pisa), played a significant role in the development of the gravitational-wave astronomy. From its first scientific run in 2007, the Virgo detector has constantly been upgraded over the years; since 2017, with the Advanced Virgo project, the detector reached a high sensitivity that allowed the detection of several classes of sources and to investigate new physics. This work reports the main hardware upgrades of the detector and the main astrophysical results from the latest five years; future prospects for the Virgo detector are also presented.

Astrophysical Neutrinos in Testing Lorentz Symmetry

An overview of searches related to neutrinos of astronomical and astrophysical origin performed within the framework of the Standard-Model Extension is provided. For this effective field theory, key definitions, intriguing physical consequences, and the mathematical formalism are summarized within the neutrino sector to search for effects from a background that could lead to small deviations from Lorentz symmetry. After an introduction to the fundamental theory, examples of various experiments within the astronomical and astrophysical context are provided. Order-of-magnitude bounds of SME coefficients are shown illustratively for the tight constraints that this sector allows us to place on such violations.

New Opportunities at the Next-Generation Neutrino Experiments (Part 1: BSM Neutrino Physics and Dark Matter

With the advent of a new generation of neutrino experiments which leverage high-intensity neutrino beams for precision neutrino oscillation parameter and for CP violation phase measurements, it is timely to explore physics topics beyond the standard neutrino-related physics. Given that beyond the standard model (BSM) physics phenomena have been mostly sought at high-energy regimes, such as the LHC at CERN, the exploration of BSM physics in neutrino experiments will enable complementary measurements at the energy regimes that balance that of the LHC. This is in concert with new ideas for high-intensity beams for fixed target and beam-dump experiments world-wide. The combination of the high intensity beam facilities and large mass detectors with highly precise track and energy measurements, excellent timing resolution, and low energy thresholds will help make BSM physics reachable even in low energy regimes in accelerator-based experiments and searches for BSM phenomena from cosmogenic origin. Therefore, it is conceivable that BSM topics could be the dominant physics topics in the foreseeable future. In this spirit, this paper provides a review of the current theory landscape theory in neutrino experiments in two selected areas of the BSM topics - dark matter and neutrino related BSM - and summarizes the current results from existing neutrino experiments for benchmark. This paper then provides a review of upcoming neutrino experiments and their capabilities to set the foundation for potential reach in BSM physics in the two themes. One of the most important outcomes of this paper is to ensure theoretical and simulation tools exist to perform studies of these new areas of physics from the first day of the experiments, such as DUNE and Hyper-K. Tasks to accomplish this goal, and the time line for them to be completed and tested to become reliable tools in a timely fashion are also discussed.

Observation of Atmospheric Neutrinos

In 1998, the Super-Kamiokande discovered neutrino oscillation using atmospheric neutrino anomalies. It was the first direct evidence of neutrino mass and the first phenomenon to be discovered beyond the standard model of particle physics. Recently, more precise measurements of neutrino oscillation parameters using atmospheric neutrinos have been achieved by several detectors, such as Super-Kamiokande, IceCube, and ANTARES. In addition, precise predictions and measurements of atmospheric neutrino flux have been performed. This paper presents the history, current status, and future prospects of the atmospheric neutrino observation.

Neutrino oscillations and instabilities in degenerate relativistic astrophysical plasmas

We set up a proposal to extend significantly recent works on neutrino-plasma interaction, allowing the possibility of deep degenerate and relativistic electrons, which are often present in compact stars such as high-density white dwarfs. The methodology involves the covariant hydrodynamic formulation of ultradense plasmas. We propose the generalization of previous studies, on the interaction between ion-acoustic waves and resonant neutrino flavor oscillations in a mixed neutrino beam, admitting degenerate and relativistic electron populations. Destabilization of the ion acoustic wave has higher growth rates, thanks to the very high densities present in plasmas under these extreme conditions. We take into account applications to white dwarf stars in the process of collapsing, producing type II supernovas.

AMON Multimessenger Alerts: Past and Future

The Astrophysical Multimessenger Observatory Network (AMON) was founded to tie the world’s high-energy and multimessenger observatories into a single network, with the purpose to enable the discovering of multimessenger sources, to exploit these sources for purposes of astrophysics, fundamental physics, and cosmology, and to explore archival datasets for evidence of multimessenger source populations. Contributions of AMON to date include the GCN prompt alerts for likely-cosmic neutrinos, multiple follow-up campaigns for likely-cosmic neutrinos including the IceCube-170922A event, and several archival searches for transient and flaring γ + ν and ν + CR multimessenger sources. Given the new dawn of multimessenger astronomy recently realized with the detection of the neutron binary star merger and the possible γ + ν coincidence detection from the blazar TXS0506+056, in 2019, we are planning to commission several multimessenger alert streams, including GW + γ and high-energy γ + ν coincidence alerts. We will briefly summarize the current status of AMON and review our monitoring plans for high-energy and multimessenger AMON alerts during what promises to be a very exciting year for multimessenger astrophysics.

Invisible Neutrino Decay Could Resolve IceCube's Track and Cascade Tension

The IceCube Neutrino Observatory detects high energy astrophysical neutrinos in two event topologies: tracks and cascades. Since the flavor composition of each event topology differs, tracks and cascades can be used to test the neutrino properties and the mechanisms behind the neutrino production in astrophysical sources. Assuming a conventional model for the neutrino production, the IceCube data sets related to the two channels are in >3σ tension with each other. Invisible neutrino decay with lifetime τ/m=10^{2}  s/eV solves this tension. Noticeably, it leads to an improvement over the standard nondecay scenario of more than 3σ while remaining consistent with all other multimessenger observations. In addition, our invisible neutrino decay model predicts a reduction of 59% in the number of observed ν_{τ} events which is consistent with the current observational deficit.

Possible explanation of the neutrino signal from SN1987A detected with the LSD

On February 23 1987 in 2:52 UT the neutrino telescope LSD under Mont Blanc detected neutrino signal, which could not be explained within the framework of the standard collapse model. We show that the LSD signal could be a consequence of the detection of gamma-quanta emitted from neutron-capture reactions on by iron nuclei contained in the composition of the experimental setup. Neutrons are produced in neutrino-nuclei reactions in the surrounding granite rock and steel structures of the detector.

Neutrino Intensity Interferometry: Measuring Protoneutron Star Radii During Core-Collapse Supernovae

Intensity interferometry is a technique that has been used to measure the size of sources ranging from the quark-gluon plasma formed in heavy ion collisions to the radii of stars. We investigate using the same technique to measure protoneutron star (PNS) radii with the neutrino signal received from a core-collapse supernovae. Using a full wave-packet analysis, including the neutrino mass for the first time, we derive criteria where the effect can be expected to provide the desired signal, and find that neutrinos from the next Galactic supernova should contain extractable PNS radius information.

Coupling between ion-acoustic waves and neutrino oscillations

The work investigates the coupling between ion-acoustic waves and neutrino flavor oscillations in a nonrelativistic electron-ion plasma under the influence of a mixed neutrino beam. Neutrino oscillations are mediated by the flavor polarization vector dynamics in a material medium. The linear dispersion relation around homogeneous static equilibria is developed. When resonant with the ion-acoustic mode, the neutrino flavor oscillations can transfer energy to the plasma exciting a new fast unstable mode in extreme astrophysical scenarios. The growth rate and the unstable wavelengths are determined in typical type II supernova parameters. The predictions can be useful for a new indirect probe on neutrino oscillations in nature.