Search

In this paper, we explore the effects of neutrino flavor oscillations on supernova nucleosynthesis and on the neutrino signals. Our study is based on detailed information about the neutrino spectra and their time evolution from a spherically symmetric supernova model for an 18M⊙ progenitor. We find that collective neutrino oscillations are not only sensitive to the detailed neutrino energy and angular distributions at emission, but also to the time evolution of both the neutrino spectra and the electron density profile. We apply the results of neutrino oscillations to study the impact on supernova nucleosynthesis and on the neutrino signals from a Galactic supernova. We show that in our supernova model, collective neutrino oscillations enhance the production of rare isotopes 138La and 180Ta but have little impact on the νp-process nucleosynthesis. In addition, the adiabatic Mikheyev-Smirnov-Wolfenstein flavor transformation, which occurs in the C/O and He shells of the supernova, may affect the production of light nuclei such as 7Li and 11B. For the neutrino signals, we calculate the rate of neutrino events in the Super-Kamiokande detector and in a hypothetical liquid argon detector. Our results suggest the possibility of using the time profiles of the events in both detectors, along with the spectral information of the detected neutrinos, to infer the neutrino mass hierarchy. [ABSTRACT FROM AUTHOR]

We show that for the active-sterile flavor mixing parameters suggested by the reactor neutrino anomaly, substantial ve-ns and ve-vs conversion occurs in regions with an electron fraction of ≈1/3 near the core of an 8.8M⊙ electron-capture supernova. We explicitly include the feedback of such conversion on the evolution of the electron fraction in supernova ejecta. Compared to the case without such conversion, the neutron richness of the ejecta is enhanced to allow production of elements from Sr, Y, and Zr up to Cd in broad agreement with observations of the metal-poor star HD 122563 for a wide range of mixing parameters. Active-sterile flavor conversion can also strongly suppress neutrino heating at times when it is important for the revival of the shock. Our results suggest that simulations of a supernova explosion and the associated nucleosynthesis may be used to constrain active-sterile mixing parameters in combination with neutrino experiments and cosmological considerations. [ABSTRACT FROM AUTHOR]

We present the first calculations of self-coupled neutrino flavor oscillations with time integrated luminosities and energy spectra for the neutronization burst of an O-- Ne -- Mg core-collapse supernova. These calculations allow us to gauge the effects of time varying neutrino luminosity and of the bump in the electron number density profile at the base of the hydrogen envelope in O -- Ne -- Mg core-collapse Supernovae. The bump allows a significant fraction of the low-energy &ngr;e to survive by rendering their flavor-evolution nonadiabatic. Increasing the luminosity of the neutronization burst shifts the bump-affected &ngr;e to lower energy with reduced survival probability. Similarly, lowering the luminosity shifts the bump-affected neutrinos to higher energies. While these low-energy neutrinos lie near the edge of detectability, the population of bump-affected neutrinos has direct influence on the spectral swap formation in the neutrino signal at higher energies. [ABSTRACT FROM AUTHOR]

We investigate the effect of matter density fluctuations on supernova collective neutrino flavor oscillations. In particular, we use full multiangle, three-flavor, self-consistent simulations of the evolution of the neutrino flavor field in the envelope of an O-Ne-Mg core-collapse supernova at shock breakout (neutronization neutrino burst) to study the effect of the matter density "bump" left by the He-burning shell. We find a seemingly counterintuitive increase in the overall ve survival probability created by this matter density feature. We discuss this behavior in terms of the interplay between the matter density profile and neutrino collective effects. While our results give new insights into this interplay, they also suggest an immediate consequence for supernova neutrino burst detection: it will be difficult to use a burst signal to extract information on fossil burning shells or other fluctuations of this scale in the matter density profile. Consistent with previous studies, our results also show that the interplay of neutrino self-coupling and matter fluctuation could cause a significant increase in the ve survival probability at very low energy. [ABSTRACT FROM AUTHOR]

We show that flavor evolution of a system of neutrinos with continuous energy spectra as in supernovae can be understood in terms of the response of individual neutrino flavor-isospins (NFIS's) to the mean field. In the case of a system initially consisting of ve and v̄e with the same energy spectrum but different number densities, the mean field is very well approximated by the total angular momentum of a neutrino gyroscope. Assuming that NFIS evolution is independent of the initial neutrino emission angle, the so-called single-angle approximation, we find that the evolution is governed by two types of resonances driven by precession and nutation of the gyroscope, respectively. The net flavor transformation crucially depends on the adiabaticity of evolution through these resonances. We show that the results for the system of two initial neutrino species can be extended to a system of four species with the initial number densities of ve and v̄e significantly larger than those of vx and v̄x. Further, we find that when the dependence on the initial neutrino emission angle is taken into account in the multiangle approximation, nutation of the mean field is quickly damped out and can be neglected. In contrast, precession-driven resonances still govern the evolution of NFIS's with different energy and emission angles just as in the single-angle approximation. Our pedagogical and analytic study of collective neutrino oscillations in supernovae provides some insights into these seemingly complicated yet fascinating phenomena. [ABSTRACT FROM AUTHOR]

We perform numerical simulations of fast collective neutrino flavor conversions in an one-dimensional box mimicking a system with the periodic boundary condition in one spatial direction and translation symmetry in the other two dimensions. We evolve the system over several thousands of the characteristic timescale (inverse of the interaction strength) with different initial νe to νe number density ratios and different initial seed perturbations. We find that small scale structures are formed due to the interaction of the flavor waves. This results in a nearly flavor depolarization in a certain neutrino phase space, when averaged over the entire box. Specifically, systems with initially equal number of νe and ¯νe can reach full flavor depolarization for the entire neutrino electron lepton number (νELN) angular spectra. For systems with initially unequal νe and νe, flavor depolarization can only be reached in one side of the νELN spectra, dictated by the net neutrino e-x lepton number conservation. Quantitatively small differences depending on the initial perturbations are also found when different perturbation seeds are applied. Our numerical study here provides new insights for efforts aiming to include impact of fast flavor conversions in astrophysical simulations while calls for better analytical understanding accounting for the evolution of fast flavor conversions. [ABSTRACT FROM AUTHOR]

Neutrinos emitted in the coalescence of two neutron stars affect the dynamics of the outflow ejecta and the nucleosynthesis of heavy elements. In this work, we analyze the neutrino emission properties and the conditions leading to the growth of flavor instabilities in merger remnants consisting of a hypermassive neutron star and an accretion disk during the first 10 ms after the merger. The analyses are based on hydrodynamical simulations that include a modeling of neutrino emission and absorption effects via the "improved leakage-equilibration-absorption scheme" (ILEAS). We also examine the nucleosynthesis of the heavy elements via the rapid neutron-capture process (r-process) inside the material ejected during this phase. The dominant emission of ¯νe over νe from the merger remnant leads to favorable conditions for the occurrence of fast pairwise flavor conversions of neutrinos, independent of the chosen equation of state or the mass ratio of the binary. The nucleosynthesis outcome is very robust, ranging from the first to the third r-process peaks. In particular, more than 10-5 M⊙ of strontium are produced in these early ejecta that may account for the GW170817 kilonova observation. We find that the amount of ejecta containing free neutrons after the r-process freeze-out, which may power early-time UV emission, is reduced by roughly a factor of 10 when compared to simulations that do not include weak interactions. Finally, the potential flavor equipartition between all neutrino flavors is mainly found to affect the nucleosynthesis outcome in the polar ejecta within ≲30°, by changing the amount of the produced iron-peak and first-peak nuclei, but it does not alter the lanthanide mass fraction therein. [ABSTRACT FROM AUTHOR]

The remnant of neutron star mergers is dense in neutrinos. By employing inputs from one hydrodynamical simulation of a binary neutron star merger remnant with a black hole of 3 M⊙ in the center, dimensionless spin parameter 0.8 and an accretion torus of 0.3 M⊙, the neutrino emission properties are investigated as the merger remnant evolves. Initially, the local number density of ¯νe is larger than that of νe everywhere above the remnant. Then, as the torus approaches self-regulated equilibrium, the local abundance of neutrinos overcomes that of antineutrinos in a funnel around the polar region. The region where the fast pairwise flavor conversions can occur shrinks accordingly as time evolves. Still, we find that fast flavor conversions do affect most of the neutrino-driven ejecta. Assuming that fast flavor conversions lead to flavor equilibration, a significant enhancement of nuclei with mass numbers A>130 is found as well as a change of the lanthanide mass fraction by more than a factor of a thousand. Our findings hint towards a potentially relevant role of neutrino flavor oscillations for the prediction of the kilonova (macronova) light curves and motivate further work in this direction. [ABSTRACT FROM AUTHOR]

The massive neutron star (NS) or black hole (BH) accretion disk resulting from NS-NS or NS-BH mergers is dense in neutrinos. We present the first study on the role of angular distributions in the neutrino flavor conversion above the remnant disk. In particular, we focus on "fast" pairwise conversions whose rate depends on the local angular intensity of the electron lepton number carried by neutrinos. Because of the emission geometry and the flux density of νe being larger than that of νe, fast conversions prove to be a generic phenomenon in NS-NS and NS-BH mergers for physically motivated disturbances in the mean field of flavor coherence. Our findings suggest that, differently from the core-collapse supernova case, fast flavor conversions seem to be unavoidable in compact mergers and could have major consequences for the jet dynamics and the synthesis of elements above the remnant disk. [ABSTRACT FROM AUTHOR]

We study the neutrino flavor evolution in the neutrino-driven wind from a binary neutron star merger remnant consisting of a massive neutron star surrounded by an accretion disk. With the neutrino emission characteristics and the hydrodynamical profile of the remnant consistently extracted from a three-dimensional simulation, we compute the flavor evolution by taking into account neutrino coherent forward scattering off ordinary matter and neutrinos themselves. We employ a "single-trajectory" approach to investigate the dependence of the flavor evolution on the neutrino emission location and angle. We also show that the flavor conversion in the merger remnant can affect the (anti)neutrino absorption rates on free nucleons and may thus impact the r-process nucleosynthesis in the wind. We discuss the sensitivity of such results on the change of neutrino emission characteristics, also from different neutron star merger simulations. [ABSTRACT FROM AUTHOR]

We examine the constraints on sub-GeV dark sector particles set by the proto-neutron star cooling associated with the core-collapse supernova event SN1987a. Considering explicitly a dark photon portal dark sector model, we compute the relevant interaction rates of dark photon (A′) and dark fermion (χ) with the Standard Model particles as well as their self-interaction inside the dark sector. We find that even with a small dark sector fine structure constant αD≪1, dark sector self-interactions can easily lead to their own self-trapping. This effect strongly limits the energy luminosity carried away by dark sector particles from the supernova core and thus drastically affects the parameter space that can be constrained by SN1987a. We consider specifically two mass ratios mA′=3mχ and 3mA′=mχ which represent scenarios where the decay of A′ to χχ is allowed or not. For mA′=3mχ, we show that this effect can completely evade the supernova bounds on widely examined dark photon parameter space for a dark sector with αD≳10-7. In particular, for the mass range mχ≲20 MeV, supernova bounds can only be applied to weakly self-interacting dark sector with αD≲10-15. For 3mA′=mχ, bounds in regions where αD≳10-7 for mχ≲20 MeV can be evaded similarly. Our findings thus imply that the existing supernova bounds on light dark particles can be generally eluded by a similar self-trapping mechanism. This also implies that nonstandard strongly self-interacting neutrino is not consistent with the SN1987a observation. Same effects can also take place for other known stellar bounds on dark sector particles. [ABSTRACT FROM AUTHOR]

We revisit the signatures from collisions of cosmic rays on sub-GeV dark matter (DM) in the Milky Way. In addition to the upscattered DM component that can be probed by existing DM and neutrino experiments widely discussed, we examine the associated signals in γ rays and neutrinos that span a wide energy range due to the inelastic scatterings. Assuming a simple vector portal DM model for illustration, we compute both the upscattered DM flux by cosmic-ray protons and the resulting emission of secondary γ rays and high-energy neutrinos from proton excitation, hadronization, and the subsequent meson decay. We derive limits on coupling constants in the vector portal model using data from the γ-ray and high-energy neutrino telescopes including Fermi, H.E.S.S., and IceCube. These limits are compared to those obtained by considering the upscattered DM signals at the low-energy DM (neutrino) detectors XENON1T (MiniBooNE) and IceCube. For this particular model, the limits are set predominantly by nondetection of the upscattered DM events in XENON1T, for most of the DM mass range due to the large scattering cross section at low energies. Nevertheless, our study demonstrates that the γ-ray and neutrino signals, traditionally considered as indirect probes for DM annihilation and decay, can also be directly used to constrain the DM-nucleon interaction in complementary to the direct search experiments. [ABSTRACT FROM AUTHOR]

We propose a new constraint on light (sub-GeV) particles beyond the Standard Model that can be produced inside the protoneutron star core resulting from the core-collapse supernova explosion. It is derived by demanding that the energy carried by exotic particles being transferred to the progenitor stellar envelopes not exceed the explosion energy of ≲2×1051 erg of observed supernovae. We show specifically that for the case of a dark photon which kinetically mixes with the SM photon and decays predominantly to an e± pair, a smaller mixing parameter of 1 order of magnitude below the well-established supernova cooling bound can be excluded. Furthermore, our bound fills the gap between the cooling bound and the region constrained by (non)observation of γ rays produced from supernovae for dark photons lighter than ∼20 MeV. Our result also rules out the possibility of aiding successful supernova explosions by transferring energy from the supernova core to the shock with exotic particles. [ABSTRACT FROM AUTHOR]

We investigate correlated gravitational wave and neutrino signals from rotating core-collapse supernovae with simulations. Using an improved mode identification procedure based on mode function matching, we show that a linear quadrupolar mode of the core produces a dual imprint on gravitational waves and neutrinos in the early post-bounce phase of the supernova. The angular harmonics of the neutrino emission are consistent with the mode energy around the neutrinospheres, which points to a mechanism for the imprint on neutrinos. Thus, neutrinos carry information about the mode amplitude in the outer region of the core, whereas gravitational waves probe deeper in. We also find that the best-fit mode function has a frequency bounded above by ∼420 Hz, and yet the mode's frequency in our simulations is ∼15% higher, due to the use of Newtonian hydrodynamics and a widely used pseudo-Newtonian gravity approximation. This overestimation is particularly important for the analysis of gravitational wave detectability and asteroseismology, pointing to limitations of pseudo-Newtonian approaches for these purposes, possibly even resulting in excitation of incorrect modes. In addition, mode frequency matching (as opposed to mode function matching) could be resulting in mode misidentification in recent work. Lastly, we evaluate the prospects of a multimessenger detection of the mode using current technology. The detection of the imprint on neutrinos is most challenging, with a maximum detection distance of ∼1 kpc using the IceCube Neutrino Observatory. The maximum distance for detecting the complementary gravitational wave imprint is ∼5 kpc using Advanced LIGO at design sensitivity. [ABSTRACT FROM AUTHOR]