Supernova Neutrino Spectra Research Articles

Shedding light on the [formula omitted] tension with supernova neutrinos

One long-standing tension in the determination of neutrino parameters is the mismatched value of the solar mass square difference, Δm212, measured by different experiments: the reactor antineutrino experiment KamLAND finds a best fit larger than the one obtained with solar neutrino data. Even if the current tension is mild (∼1.5σ), it is timely to explore if independent measurements could help in either closing or reassessing this issue. In this regard, we explore how a future supernova burst in our galaxy could be used to determine Δm212 at the future Hyper-Kamiokande detector, and how this could contribute to the current situation. We study Earth matter effects for different models of supernova neutrino spectra and supernova orientations. We find that, if supernova neutrino data prefers the KamLAND best fit for Δm212, an uncertainty similar to the current KamLAND one could be achieved. On the contrary, if it prefers the solar neutrino data best fit, the current tension with KamLAND results could grow to a significance larger than 5σ. Furthermore, supernova neutrinos could significantly contribute to reducing the uncertainty on sin2⁡θ12.

Bayesian inference of supernova neutrino spectra with multiple detectors

We implement the Bayesian inference to retrieve energy spectra of all neutrinos from a galactic core-collapse supernova (CCSN). To achieve high statistics and full sensitivity to all flavours of neutrinos, we adopt a combination of several reaction channels from different large-scale neutrino observatories, namely inverse beta decay on proton and elastic scattering on electron from Hyper-Kamiokande (Hyper-K), charged current absorption on Argon from Deep Underground Neutrino Experiment (DUNE) and coherent elastic scattering on Lead from RES-NOVA. Assuming no neutrino oscillation or specific oscillation models, we obtain mock data for each channel through Poisson processes with the predictions, for a typical source distance of 10 kpc in our Galaxy, and then evaluate the probability distributions for all spectral parameters of theoretical neutrino spectrum model with Bayes' theorem. Although the results for either the electron-neutrinos or electron-antineutrinos reserve relatively large uncertainties (according to the neutrino mass ordering), a precision of a few percent (i.e., ±1% ∼ ±4% at a credible interval of 2σ) is achieved for primary spectral parameters (e.g., mean energy and total emitted energy) of other neutrino species. Moreover, the correlation coefficients between different parameters are computed as well and interesting patterns are found. Especially, the mixing-induced correlations are sensitive to the neutrino mass ordering, which potentially makes it a brand new probe to determine the neutrino mass ordering in the detection of galactic supernova neutrinos. Finally, we discuss limitations and perspectives for further improvement on our results.

Supernova Neutrino Spectra and Observations by Large Volume Telescopes

Supernova Neutrino Spectra and Observations by Large Volume Telescopes

Neutral-current supernova neutrino-nucleus scattering off I127 and Cs133

A large number of the presently running neutrino and dark-matter experiments use thallium-doped cesium-iodide CsI[Tl] crystals, sodium-doped cesium-iodide CsI[Na] crystals, or thallium-doped sodium-iodide NaI[Tl] crystals. In the present paper we calculate elastic and inelastic cross sections for neutral-current supernova-neutrino scattering off $^{127}\mathrm{I}$ and $^{133}\mathrm{Cs}$, relevant for experiments using CsI[Tl], CsI[Na], or NaI[Tl] crystals. We study also the cross sections folded with two-parameter Fermi-Dirac distributions of the supernova-neutrino spectrum. The adopted nuclear-theory framework is the microscopic quasiparticle-phonon model, able to operate in large single-particle valence bases and use G-matrix based two-nucleon interactions with a phenomenological renormalization.

Neutrinos from the cosmic noon: a probe of the cosmic star formation history

Multiple astrophysical probes of the cosmic star formation history (CSFH) indicate a period of peak star formation known as the cosmic noon between 1.5 ≲ z ≲ 3.5.In this work, we explore the potential of future measurements of the diffuse supernova neutrino background (DSNB) at the Hyper-Kamiokande (HK) experiment to be sensitive to variations in the expected star formation rate at cosmic noon. Motivated by a statistically mild discrepancy between Hα and UV/IR probes of the CSFH, which indicate a factor of ∼ 3 difference in the CSFH near the cosmic noon, we construct two benchmark hypotheses based on these different data sets. Since the cosmic noon neutrinos are redshifted to low energies, a low threshold sensitivity of any detector will be critical for discriminating between these benchmark hypotheses. We explore whether HK loaded with Gadolinium, with a positron threshold energy of 10 MeV, would be sensitive to the difference between these two CSFH hypotheses. Assuming that the supernova (SN) neutrino spectrum can be well determined by calibrating core-collapse SNe simulations to observations of nearby SNe, we find that only for very high core-collapse SN temperatures, HK would be sensitive to the difference in the benchmark CSFHs, and even then, over a 10–30 year time scale. Future experiments must lower their thresholds to be more sensitive to cosmic noon neutrinos.

Review of uncertainties in the cosmic supernova relic neutrino background

We review the computation of and associated uncertainties in the current understanding of the relic neutrino background due to core-collapse supernovae, black hole formation and neutron star merger events. We consider the current status of uncertainties due to the nuclear equation of state (EoS), the progenitor masses, the source supernova neutrino spectrum, the cosmological star formation rate, the stellar initial mass function, neutrino oscillations, and neutrino self-interactions. We summarize the current viability of future neutrino detectors to distinguish the nuclear EoS and the temperature of supernova neutrinos via the detected relic supernova neutrino spectrum.

Cross sections for the neutral current νe - 116Cd scattering reaction

The cross sections for neutrino scattering off the 116Cd nucleus have been computed by utilizing the Quasi-particle Random Phase Approximation (QRPA). An- gular and initial energy dependence of the neutrino-nucleus cross sections have been calculated at low and intermediate electron neutrino energies up to 100 MeV. By solving the QRPA equations and fixing the appropriate parameters the lowest lying excitation energies spectrum was reproduced. The contributions from multipole ex- citations was examined. The obtained results could be used for studying the nuclear response of this isotope to supernova neutrino spectra.

Using the folding method for studying the nuclear response to Supernova neutrino spectra

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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.

EoS Dependence of the Relic Supernova Neutrino Spectrum

Understanding the mechanism of core-collapse supernova explosions requires knowledge of the nuclear equation of state (EoS). Recent multi-dimensional numerical simulations indicate that explosions are possible. Nevertheless, it is not yet fully understood which equation of state is realized in the proto-neutron star formed during SN explosions. We examine the EoS sensitivity of the relic supernova neutrino spectrum as a probe of the nuclear EoS. This sensitivity arises largely from the contribution to neutrino emission from failed supernovae. We consider a variety of astrophysical scenarios, which include different progenitor masses for a successful explosion, the cosmological star formation rate, starbursts, quiescent star formation, and the metallicity dependence of the initial mass function. We find that the EoS signature remains robust under a variety of conditions. We demonstrate the viability of future neutrino detectors to distinguish the nuclear EoS via the relic supernova neutrino spectrum.

What can we learn on supernova neutrino spectra with water Cherenkov detectors?

We investigate the precision with which the supernova neutrino spectra can be reconstructed in water Cherenkov detectors, in particular the large scale Hyper-Kamiokande and Super-Kamiokande. To this aim, we consider quasi-thermal neutrino spectra modified by the Mikheev-Smirnov-Wolfenstein effect for the case of normal ordering. We perform three 9 degrees of freedom likelihood analyses including first inverse-beta decay only, then the combination of inverse beta decay and elastic scattering on electrons and finally a third analysis that also includes neutral scattering neutrino-oxygen events. A tenth parameter is added in the analyses to account for the theoretical uncertainty on the neutral current neutrino-oxygen cross section. By assuming a 100% efficiency in Hyper-Kamiokande, we show that one can reconstruct the electron antineutrino average energy and pinching parameter with an accuracy of ∼2% and ∼7% percent respectively, while the antineutrino integrated luminosity can be pinned down at ∼3% percent level. As for the muon and tau neutrinos, the average energy and the integrated luminosity can be measured with ∼7% precision. These results represent a significant improvement with respect Super-Kamiokande, particularly for the pinching parameter defining the electron antineutrino spectra. As for electron neutrinos, the determination of the emission parameters requires the addition of supplementary detection channels.

Towards a complete reconstruction of supernova neutrino spectra in future large liquid-scintillator detectors

In this paper, we show how to carry out a relatively more realistic and complete reconstruction of supernova neutrino spectra in the future large liquid-scintillator detectors, by implementing the method of singular value decomposition with a proper regularization. For a core-collapse supernova at a distance of $10~{\rm kpc}$ in the Milky Way, its $\overline{\nu}^{}_e$ spectrum can be precisely determined from the inverse beta-decay process $\overline{\nu}^{}_e + p \to e^+ + n$, for which a $20~{\rm kiloton}$ liquid-scintillator detector with the resolution similar to the Jiangmen Underground Neutrino Observatory (JUNO) may register more than 5000 events. We have to rely predominantly on the elastic neutrino-electron scattering $\nu + e^- \to \nu + e^-$ and the elastic neutrino-proton scattering $\nu + p \to \nu + p$ for the spectra of $\nu^{}_e$ and $\nu^{}_x$, where $\nu$ denotes collectively neutrinos and antineutrinos of all three flavors and $\nu^{}_x$ for $\nu^{}_\mu$ and $\nu^{}_\tau$ as well as their antiparticles. To demonstrate the validity of our approach, we also attempt to reconstruct the neutrino spectra by using the time-integrated neutrino data from the latest numerical simulations of delayed neutrino-driven supernova explosions.

RED-SUPERGIANT AND SUPERNOVA RATE PROBLEMS: IMPLICATION FOR THE RELIC SUPERNOVA NEUTRINO SPECTRUM

ABSTRACT Direct observations of core-collapse supernovae (SNe) and their red supergiant (RSG) progenitors suggest that the upper mass limit of RSGs may be only about 16.5 – 18 M ⊙ , while the standard theoretical value is as much as 25 M ⊙ . We investigate the possibility that RSGs with m > 16.5 – 18 M ⊙ end their lives as failed supernovae (fSNe) and analyze their contribution to the relic supernova neutrino spectrum. We show that adopting this mass limit simultaneously solves both the RSG problem and the supernova rate problem. In addition, energetic neutrinos that originated from fSNe are sensitive to the explosion mechanism, and in particular, to the nuclear equation of state (EOS). We show that this solution to the RSG problem might also be used to constrain the EOS for failed supernovae.

Shell model studies for nuclear astrophysics

Shell model studies have contributed in recent years significantly to improve nuclear input required in simulations of the dynamics of astrophysical objects and their associated nucleosynthesis. This manuscript highlights a few examples like electron capture rates of importance for the evolution of core-collapse supernovae and the nucleosynthesis in thermonuclear supernovae, neutrino-nucleus cross sections with relevance to the supernova neutrino spectra and finally half lives of neutron-rich nuclei with magic neutron numbers which serve as waiting points in the mass flow of the astrophysical r-process.

Earth matter effects on supernova neutrinos in large-volume detectors

Neutrino oscillations in the Earth matter may introduce peculiar modulations in the supernova (SN) neutrino spectra. The detection of this effect has been proposed as diagnostic tool for the neutrino mass hierarchy. We perform an updated study on the observability of this effect at large next-generation underground detectors (i.e., 0.4 Mton water Cherenkov, 50 kton scintillation and 100 kton liquid Argon detectors) based on neutrino fluxes from state-of-the-art SN simulations and accounting for statistical fluctuations via Montecarlo simulations. Since the average energies predicted by recent simulations are lower than previously expected and a tendency towards the equalization of the neutrino fluxes appears during the SN cooling phase, the detection of the Earth matter effect will be more challenging than expected from previous studies. We find that none of the proposed detectors shall be able to detect the Earth modulation for the neutrino signal of a typical galactic SN at 10 kpc. It should be observable in a 100 kton liquid Argon detector for a SN at few kpc and all three detectors would clearly see the Earth signature for very close-by stars only (d∼200pc).

SUPERNOVA NEUTRINO LIGHT CURVES AND SPECTRA FOR VARIOUS PROGENITOR STARS: FROM CORE COLLAPSE TO PROTO-NEUTRON STAR COOLING

We present a new series of supernova neutrino light curves and spectra calculated by numerical simulations for a variety of progenitor stellar masses (13-50Msolar) and metallicities (Z = 0.02 and 0.004), which would be useful for a broad range of supernova neutrino studies, e.g., simulations of future neutrino burst detection by underground detectors, or theoretical predictions for the relic supernova neutrino background. To follow the evolution from the onset of collapse to 20 s after the core bounce, we combine the results of neutrino-radiation hydrodynamic simulations for the early phase and quasi-static evolutionary calculations of neutrino diffusion for the late phase, with different values of shock revival time as a parameter that should depend on the still unknown explosion mechanism. We here describe the calculation methods and basic results including the dependence on progenitor models and the shock revival time. The neutrino data are publicly available electronically.

High-resolution supernova neutrino spectra represented by a simple fit

To study the capabilities of supernova neutrino detectors, the instantaneous spectra are often represented by a quasi-thermal distribution of the form f(E) = E^alpha e^{-(alpha+1)E/E_{av}} where E_{av} is the average energy and alpha a numerical parameter. Based on a spherically symmetric supernova model with full Boltzmann neutrino transport we have, at a few representative post-bounce times, re-converged the models with vastly increased energy resolution to test the fit quality. For our examples, the spectra are well represented by such a fit in the sense that the counting rates for a broad range of target nuclei, sensitive to different parts of the spectrum, are reproduced very well. Therefore, the mean energy and root-mean-square energy of numerical spectra hold enough information to provide the correct alpha and to forecast the response of multi-channel supernova neutrino detection.

Can one observe Earth matter effects with supernova neutrinos?

Neutrino oscillations in the Earth matter may introduce peculiar modulations in the supernova (SN) neutrino spectra. The detection of this effect has been proposed as diagnostic tool for the neutrino mass hierarchy at "large" 1-3 leptonic mixing angle theta13. We perform an updated study on the observability of this effect at large next-generation underground detectors (i.e., 0.4 Mton water Cherenkov, 50 kton scintillation and 100 kton liquid Argon detectors) based on neutrino fluxes from state-of-the-art SN simulations and accounting for statistical fluctuations via Montecarlo simulations. Since the average energies predicted by recent simulations are lower than previously expected and a tendency towards the equalization of the neutrino fluxes appears during the SN cooling phase, the detection of the Earth matter effect will be more challenging than expected from previous studies. We find that none of the proposed detectors shall be able to detect the Earth modulation for the neutrino signal of a typical galactic SN at 10 kpc. It should be observable in a 100 kton liquid Argon detector for a SN at few kpc and all three detectors would clearly see the Earth signature for very close-by stars only (d ~ 0.2 kpc). Finally, we show that adopting IceCube as co-detector together with a Mton water Cherenkov detector is not a viable option either.

Detailed study of the neutral-current neutrino–nucleus scattering off the stable Mo isotopes

Abstract For neutrino detection and for various applications in astrophysics the knowledge of the nuclear responses to astrophysical neutrinos is crucial. Recent studies of neutrino interactions with the 100 Mo nucleus and the other stable molybdenum isotopes are important for the planned MOON (Mo Observatory of Neutrinos) detector. To this aim, in the present work we perform detailed nuclear structure calculations for the neutral-current neutrino–nucleus scattering off the stable molybdenum isotopes. We focus on the differential and total neutrino–nucleus cross sections as well as on flux averaged cross sections to various supernova neutrino spectra. We also propose a more efficient method for the computations of the corresponding nuclear matrix elements. By employing this method we extend our previous calculations for the odd isotopes ( 95 Mo and 97 Mo) where also couplings to high-lying QRPA (quasiparticle random-phase approximation) phonons are included in the quasiparticle-phonon basis. It is established in this work that the inclusion of high-lying QRPA excitations are essential for the description of the neutrino–nucleus scattering off open-shell odd-mass nuclei.

Analyzing astrophysical neutrino signals using realistic nuclear structure calculations and the convolution procedure

Convoluted differential and total cross sections of inelastic $\ensuremath{\nu}$ scattering on ${}^{128,130}$Te isotopes are computed from the original cross sections calculated previously using the quasiparticle random-phase approximation. We adopt various spectral distributions for the neutrino energy spectra such as the common two-parameter Fermi-Dirac and power-law distributions appropriate to explore nuclear detector responses to supernova neutrino spectra. We also concentrate on the use of low-energy $\ensuremath{\beta}$-beam neutrinos, originating from boosted ${\ensuremath{\beta}}^{\ensuremath{-}}$-radioactive ${}^{6}$He ions, to decompose original supernova (anti)neutrino spectra that are subsequently employed to simulate total cross sections of the reactions ${}^{130}\mathrm{Te}{(\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\ensuremath{\nu}},{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{\ensuremath{\nu}}}^{\ensuremath{'}})}^{130}{\mathrm{Te}}^{*}$. The concrete nuclear regimes selected, ${}^{128,130}$Te, are contents of the multipurpose CUORE and COBRA rare event detectors. Our present investigation may provide useful information about the efficiency of the Te detector medium of the above experiments in their potential use in supernova neutrino searches.