Diffuse Supernova Neutrino Background Research Articles

Impact of binary interactions on the diffuse supernova neutrino background

Binary interactions, especially mass transfer and mergers, can strongly influence the evolution of massive stars and change their final properties and the occurrence of supernovae. Here, we investigate how binary interactions affect predictions of the diffuse flux of neutrinos. By performing stellar population syntheses including prescriptions for binary interactions, we show that the resulting detection rates of the diffuse supernova neutrino background is enhanced by 15%-20% compared to estimates without binary considerations. A source of significant uncertainty arises due to the presently sparse knowledge of the evolution of rapidly rotating carbon-oxygen cores, especially those created as a result of mergers near the white dwarf to core collapse boundary. The enhancement effect may be as small as a few percent if the effects of rotation in postmerger systems are neglected, or as large as 75% if trends are extrapolated. Our estimates serve to highlight that binary effects can be important.

Detecting the diffuse supernova neutrino background in the future water-based liquid scintillator detector Theia

A large-scale neutrino observatory based on Water-based Liquid Scintillator (WbLS) will be excellently suited for a measurement of the Diffuse Supernova Neutrino Background (DSNB). The WbLS technique offers high signal efficiency and effective suppression of the otherwise overwhelming background from neutral-current interactions of atmospheric neutrinos. To illustrate this, we investigate the DSNB sensitivity for two configurations of the future Theia detector by developing the expected signal and background rejection efficiencies along a full analysis chain. Based on a statistical analysis of the remaining signal and background rates, we find that a rather moderate exposure of 190kt$\cdot$yrs will be sufficient to claim a ($5\sigma$) discovery of the faint DSNB signal for standard model assumptions. We conclude that, in comparison with other experimental techniques, WbLS offers the highest signal efficiency of more than 80\% and best signal significance over background.

Resonant neutrino self-interactions

If neutrinos have self-interactions, these will induce scatterings between astrophysical and cosmic neutrinos. Prior work proposed to look for possible resulting resonance features in astrophysical neutrino spectra in order to seek a neutrino self-interaction which can be either diagonal in the neutrino flavor space or couple different neutrino flavors. The calculation of the astrophysical spectra involves either a Monte Carlo simulation or a computationally intensive numerical integration of an integro-partial-differential equation. As a result only limited regions of the neutrino self-interaction parameter space have been explored, and only flavor-diagonal self-interactions have been considered. Here, we present a fully analytic form for the astrophysical neutrino spectra for arbitrary neutrino number and arbitrary self-coupling matrix that accurately obtains the resonance features in the observable neutrino spectra. The results can be applied to calculations of the diffuse supernova neutrino background and of the spectrum from high-energy astrophysical neutrino sources. We illustrate with a few examples.

Fundamental physics with the diffuse supernova background neutrinos

The Universe is awash with tens-of-MeV neutrinos of all species coming from all past core-collapse supernovae. These have never been observed, but this state of affairs will change in the near future. In the less than ten years, the Super-Kamiokande experiment, loaded with gadolinium, is expected to collect dozens of events induced by the scattering of neutrinos from the diffuse supernova neutrino background (DSNB). Next-generation projects, including Hyper-Kamiokande and Theia, are expected to collect data samples with hundreds of DSNB events after a decade of running. Here, we study quantitatively how well the DSNB, including its energy spectrum, will be measured by different current or upcoming large neutrino detectors. We analyze the simulated data in order to estimate how well measurements of the DSNB can be used to inform research topics in cosmology -- including measurements of the Hubble parameter -- astrophysics -- including the star-formation-rate -- and particle physics -- including the neutrino lifetime and the possibility that neutrinos are pseudo-Dirac fermions.

Search for hep solar neutrinos and the diffuse supernova neutrino background using all three phases of the Sudbury Neutrino Observatory

A search has been performed for neutrinos from two sources, the $hep$ reaction in the solar $pp$ fusion chain and the $\nu_e$ component of the diffuse supernova neutrino background (DSNB), using the full dataset of the Sudbury Neutrino Observatory with a total exposure of 2.47 kton-years after fiducialization. The $hep$ search is performed using both a single-bin counting analysis and a likelihood fit. We find a best-fit flux that is compatible with solar model predictions while remaining consistent with zero flux, and set a one-sided upper limit of $\Phi_{hep} < 30\times10^{3}~\mathrm{cm}^{-2}~\mathrm{s}^{-1}$ [90% credible interval (CI)]. No events are observed in the DSNB search region, and we set an improved upper bound on the $\nu_e$ component of the DSNB flux of $\Phi^\mathrm{DSNB}_{\nu_e} < 19~\textrm{cm}^{-2}~\textrm{s}^{-1}$ (90% CI) in the energy range $22.9 < E_\nu < 36.9$~MeV.

Neutrino and Positron Constraints on Spinning Primordial Black Hole Dark Matter.

Primordial black holes can have substantial spin-a fundamental property that has a strong effect on its evaporation rate. We conduct a comprehensive study of the detectability of primordial black holes with non-negligible spin, via the searches for the neutrinos and positrons in the MeV energy range. Diffuse supernova neutrino background searches and observation of the 511keV gamma-ray line from positrons in the Galactic center set competitive constraints. Spinning primordial black holes are probed up to a slightly higher mass range compared to nonspinning ones. Our constraint using neutrinos is slightly weaker than that due to the diffuse gamma-ray background, but complementary and robust. Our positron constraints are typically weaker in the lower mass range and stronger in the higher mass range for the spinning primordial black holes compared to the nonspinning ones. They are generally stronger than those derived from the diffuse gamma-ray measurements for primordial black holes having masses greater than a few ×10^{16} g.

Physics prospects of the JUNO experiment

JUNO is a 20 kton multi-purpose liquid scintillator detector currently being built in China in a dedicated underground laboratory and expected to complete the detector construction in 2021. JUNO primary physics goal is the determination of the neutrino mass ordering, with a significance of 3-4 sigma in six years of data taking, by measuring the oscillation pattern of electron antineutrinos coming from two nuclear power plants at a baseline of about 53 km. Besides this fundamental aim, its large target mass, unprecedented energy resolution of 3% at 1 MeV, and vertex reconstruction capability will provide vast opportunities in particle physics and astrophysics. JUNO will have a very rich physics program, which includes the precise measurement at a sub-percent level of the solar neutrino oscillation parameters, the detection of low-energy neutrinos coming from galactic core-collapse supernova, the measurement of the diffuse supernova neutrino background, the detection of neutrinos coming from the Sun and the Earth (geo-neutrinos). In this paper I will give an overview on the JUNO physics potential and discuss the performance of the JUNO detector for the various proposed measurements.

Geant4 based Simulation Study for Super-Kamiokande

Super-Kamiokande (SK) will start a new phase “SK-Gd” from next year. Currently, SK uses Geant3 based simulation, however, its development has already stopped. For the next 10 years of SK-Gd operation, updated detector simulation is essential. For diffuse supernova neutrino background search in SK-Gd, precise neutron simulation is crucial. Therefore, we developed Geant4 based SK simulation software, named’ SKG4’ . Starting from the construction of SK geometry, some comparisons with the current SK detector simulation has been done. In this presentation, the current status of the development for SKG4 and the result of the several physics simulations will be reported.

The Diffuse Supernova Neutrino Background

The Diffuse Supernova Neutrino Background (DSNB) in the MeV regime represents the cumulative cosmic neutrino emission, predominantly due to core collapse supernovae. We estimate the DSNB flux for different Star Formation Rate Density (SFRD) models. We find that the DSNB flux estimated using the SFRD derived from Fermi-LAT Collaboration et al. (2018) is significantly higher ($\approx$ 32$\%$) relative to the flux estimated using the SFRD from Madau & Fragos (2017). This depicts the sensitivity between the DSNB flux and the SFRD estimates which shows that future detection of the DSNB can be used as a valuable tool to constrain the SFRD.

The Super Kamionade Gadolinium Project

Super-Kamiokande (SK) will be upgraded to Super-Kamiokande Gd (SK-Gd). This modification will enable it to identify low energy anti-neutrinos for the world’s first observation of the Diffuse Supernova Neutrino Background (DSNB). On average, there is one core-collapse supernova somewhere in the universe each second. The neutrinos emitted from all of these supernovae since the onset of stellar formation have suffused the universe. The flux of the DSNB is expected to be several tens per square centimeter per second. Theoretical models vary, but as many as five diffused supernova neutrinos per year above 10 MeV are expected to interact in SK. However, in order to separate these signals from the much more common solar and atmospheric neutrinos and other backgrounds, we need a new detection method. In 2015, the Super-Kamiokande Collaboration approved the SK-Gd project. It is the upgrade of the SK detector via the addition of water-soluble gadolinium (Gd) salt. Since then, we have been conducting many dedicated studies and developments for deploying Gd to SK.

Constraining Chaplygin models using diffuse supernova neutrino background

In this work, we examine the possibility of using the diffuse supernova neutrino background (DSNB) to test the Chaplygin gas (CG) models of the Universe. With a typical supernova rate $R_{\mathrm{SN}}(z)$ and supernova neutrino spectrum $\mathrm{d} N(E_\nu)/\mathrm{d} E_\nu$, the DSNB flux spectrum $n(E_\nu)$ in three categories of CG models, the generalized CG (GCG), modified CG (MCG) and extended CG (ECG) models, are studied. It is found that generally the flux spectra take a form similar to a Fermi-Dirac distribution with a peak centered around 3.80-3.97 MeV. The spectrum shape and peak positions are primarily determined by $R_{\mathrm{SN}}(z)$ and $\mathrm{d} N(E_\nu)/\mathrm{d} E_\nu$ and only slightly affected by the CG models. However, the height of the spectra in each category of the CG models can vary dramatically for different models, with variances of 13.2%, 23.6% and 14.9% for GCG, MCG and ECG categories respectively. The averaged total flux in each category are also different, with the ECG model average 10.0% and 12.7% higher than that of the GCG and MCG models. These suggest that the DSNB flux spectrum height and total flux can be used to constrain the CG model parameters, and if the measured to a sub-10% accuracy, might be used to rule out some models.

Status of the Jiangmen Underground Neutrino Observatory

The Jiangmen Underground Neutrino Observatory (JUNO) is a next generation multipurpose antineutrino detector currently under construction in Jiangmen, China. The central detector, containing 20 kton of a liquid scintillator, will be equipped with ∼18 000 20 inch and 25 600 3 inch photomultiplier tubes. Measuring the reactor antineutrinos of two powerplants at a baseline of 53 km with an unprecedented energy resolution of 3%/√︀E(MeV), the main physics goal is to determine the neutrino mass hierarchy within six years of run time with a significance of 3–4q. Additional physics goals are the measurement of solar neutrinos, geoneutrinos, supernova burst neutrinos, the diffuse supernova neutrino background, and the oscillation parameters sin2 O12, Δm212, and |Δm2ee| with a precision &lt;1%, as well as the search for proton decays. The construction is expected to be completed in 2021.

Developing the MeV potential of DUNE: Detailed considerations of muon-induced spallation and other backgrounds

The Deep Underground Neutrino Experiment (DUNE) could be revolutionary for MeV neutrino astrophysics, because of its huge detector volume, unique event reconstruction capabilities, and excellent sensitivity to the $\nu_e$ flavor. However, its backgrounds are not yet known. A major background is expected due to muon spallation of argon, which produces unstable isotopes that later beta decay. We present the first comprehensive study of MeV spallation backgrounds in argon, detailing isotope production mechanisms and decay properties, analyzing beta energy and time distributions, and proposing experimental cuts. We show that above a nominal detection threshold of 5-MeV electron energy, the most important backgrounds are --- surprisingly --- due to low-A isotopes, such as Li, Be, and B, even though high-A isotopes near argon are abundantly produced. We show that spallation backgrounds can be powerfully rejected by simple cuts, with clear paths for improvements. We compare these background rates to rates of possible MeV astrophysical neutrino signals in DUNE, including solar neutrinos (detailed in a companion paper [Capozzi et al. arXiv:1808.08232 [hep-ph]]), supernova burst neutrinos, and the diffuse supernova neutrino background. Further, to aid trigger strategies, in the Appendixes we quantify the rates of single and multiple MeV events due to spallation, radiogenic neutron capture, and other backgrounds, including through pileup. Our overall conclusion is that DUNE has high potential for MeV neutrino astrophysics, but reaching this potential requires new experimental initiatives.

Recent results and future prospects of Super-Kamiokande

Abstract Super-Kamiokande (SK) is a water Cherenkov detector located 1000 m underground in Kamioka Observatory , ICRR, University of Tokyo in Japan. It consists of a cylindrical stainless steel tank, 50,000 ton of purified water, and 11,000 of 20-inch PMTs. The fiducial volume of the SK detector is 22.5 kton. The experiment was started in April 1996, and currently phase IV (SK-IV) is running. SK has been the world largest water Cherenkov detector with purified water in underground since 1996. SK has a variety of measurement or physics targets, namely, solar neutrinos , atmospheric neutrinos , supernova neutrinos, neutrinos produced by the accelerator in J-PARC (as T2K experiment), and search for nucleon decay. In near future, we are going to move to the next phase, that is SK-Gd. In the SK-Gd phase, we are planning to add 0.1% of gadolinium to the current SK detector in order to enhance neutron tagging efficiency, and then try to achieve the first observation of supernova relic neutrinos (SRN) (or diffuse supernova neutrino background (DSNB)). The initial work in this upgrade project was started in June 2018. This paper reports a brief summary of the SK experiment, recent solar neutrino results, and recent atmospheric neutrino results. As a future plan, the purpose of SK-Gd and status of the upgrade work are reported.

Probing secret interactions of eV-scale sterile neutrinos with the diffuse supernova neutrino background

Sterile neutrinos with mass in the eV-scale and large mixings of order θ0≃ 0.1 could explain some anomalies found in short-baseline neutrino oscillation data. Here, we revisit a neutrino portal scenario in which eV-scale sterile neutrinos have self-interactions via a new gauge vector boson ϕ. Their production in the early Universe via mixing with active neutrinos can be suppressed by the induced effective potential in the sterile sector. We study how different cosmological observations can constrain this model, in terms of the mass of the new gauge boson, Mϕ, and its coupling to sterile neutrinos, gs. Then, we explore how to probe part of the allowed parameter space of this particular model with future observations of the diffuse supernova neutrino background by the Hyper-Kamiokande and DUNE detectors. For Mϕ ∼ 5−10 keV and gs ∼ 10−4−10−2, as allowed by cosmological constraints, we find that interactions of diffuse supernova neutrinos with relic sterile neutrinos on their way to the Earth would result in significant dips in the neutrino spectrum which would produce unique features in the event spectra observed in these detectors.

Measuring the supernova unknowns at the next-generation neutrino telescopes through the diffuse neutrino background

The detection of the diffuse supernova neutrino background (DSNB) will preciously contribute to gauge the properties of the core-collapse supernova population. We estimate the DSNB event rate in the next-generation neutrino detectors, Hyper-Kamiokande enriched with Gadolinium, JUNO, and DUNE. The determination of the supernova unknowns through the DSNB will be heavily driven by Hyper-Kamiokande, given its higher expected event rate, and complemented by DUNE that will help in reducing the parameters uncertainties. Meanwhile, JUNO will be sensitive to the DSNB signal over the largest energy range. A joint statistical analysis of the expected rates in 20 years of data taking from the above detectors suggests that we will be sensitive to the local supernova rate at most at a 20−33% level. A non-zero fraction of supernovae forming black holes will be confirmed at a 90% CL, if the true value of that fraction is ≳20%. On the other hand, the DSNB events show extremely poor statistical sensitivity to the nuclear equation of state and mass accretion rate of the progenitors forming black holes.

Diffuse neutrino supernova background as a cosmological test

The future detection and measurement of the diffuse neutrino supernova background will provide us with information about supernova neutrino emission and the cosmic core-collapse supernova rate. Little has been said about the information that this measurement could give us about the expansion history of the Universe. The purpose of this article is to study the change of the predicted diffuse supernova neutrino background as a function of the cosmological model. In particular, we study three different models: the Λ–Cold Dark Matter model, the Logotropic universe and a bulk viscous matter-dominated universe. By fitting the free parameters of each model with the supernova Ia probe, we calculate the predicted number of events in these three models. We found that the spectra and number of events for the Λ–Cold dark matter model and the Logotropic model are almost indistinguishable, while a bulk viscous matter-dominated cosmological model predicts more events.

Diffuse supernova neutrino background from extensive core-collapse simulations of 8–100 M⊙ progenitors

We revisit the diffuse supernova neutrino background in light of recent systematic studies of stellar core collapse that reveal the quantitative impacts of the progenitor conditions on the collapse process. In general, the dependence of the progenitor on the core-collapse neutrino emission is not monotonic in progenitor initial mass, but we show that it can, at first order, be characterized by the core compactness. For the first time, we incorporate the detailed variations in the neutrino emission over the entire mass range $8$-$100 {\rm M}_\odot$, based on (i) a long-term simulation of the core collapse of a $8.8 {\rm M}_\odot$ O-Ne-Mg core progenitor, (ii) over 100 simulations of iron core collapse to neutron stars, and (iii) half a dozen simulations of core collapse to black holes (the "failed channel"). The fraction of massive stars that undergo the failed channel remains uncertain, but in view of recent simulations which reveal high compactness to be conducive to collapse to black holes, we characterize the failed fraction by considering a threshold compactness above which massive stars collapse to black holes and below which the final remnant is a neutron star. We predict that future detections of the diffuse supernova neutrino background may have the power to reveal this threshold compactness, if its value is relatively small as suggested by interpretations of several recent astronomical observations.

Study of Diffuse Supernova Neutrino Background with Modern and Future Detectors

Basic properties of the diffuse supernova neutrino background (DSNB) are reviewed. Current DSNB studies and the limits already set on the DSNB flow by the operating detectors Super-Kamiokande, SNO, and KamLAND are discussed. Prospects of DSNB studies with future high-mass neutrino detectors, such as JUNO and Hyper-Kamiokande, are considered.

Diffuse neutrinos from luminous and dark supernovae: prospects for upcoming detectors at the \U0001d4aa(10) kt scale

We estimate the Diffuse Supernova Neutrino Background (DSNB) using the simulation results for neutron star-forming and black hole-forming stellar collapses from the Garching group. Scenarios with different distributions of black-hole forming collapses with the progenitor mass are discussed, and the uncertainty on the cosmological rate of collapses is included. The ν̄e component of the DSNB above 11 MeV of energy is found to be ϕ ≃ (1.4–3.7) cm−2 s−1; the contribution of black hole-forming collapses could dominate the flux above ∼ 25 MeV . We calculate the potential of detecting the DSNB at SuperK-Gd and JUNO, in about a decade-long period of operation. We find that, in our model, it is likely that a significant excess above the background will be obtained at JUNO, while detection will be more difficult at SuperK-Gd. The potential when the two experimental results are examined jointly is discussed as well. We also consider an example of a future \U0001d4aa(10) kt slow liquid scintillator detector, and show that there the odds of detection are very good. Our results motivate experimental efforts in reducing the backgrounds due to neutral current scattering of atmospheric neutrinos in SuperK-Gd.