We investigate the multi-azimuthal angle (MAA) effect on collective neutrino oscillation by considering the three-dimensional neutrino momentum distribution in a realistic electron-capture supernova model with an $8.8 M_{\odot}$ progenitor. We find that the MAA effect induces collective flavor conversions at epochs when it is completely suppressed under the axial-symmetric approximation. This novel activity is switched on/off by the growth of the MAA instability and imprints additional time evolution in the expected neutrino event rate. We validate our results by extending the linear stability analysis into the three-flavor scheme including mixing angles, and confirm that the onset of collective neutrino oscillation matches the steep growth of flavor instability. We discuss how the MAA effect alters neutrino detection at Super-Kamiokande and DUNE.
Fast flavor conversions of supernova neutrinos, possible near the neutrinosphere, depends on an interesting interplay of collisions and neutrino oscillations. Contrary to naive expectations, the rate of self-induced neutrino oscillations, due to neutrino-neutrino forward scattering, comfortably exceeds the rate of collisions even deep inside the supernova core. Consistently accounting for collisions and oscillations, we present the first calculations to show that collisions can create the conditions for fast flavor conversions of neutrinos, but oscillations can continue without significant dam…
The supernova neutrino flavor evolution in the presence of the non-trivial neutrino magnetic moment and strong magnetic field is numerically derived using the two-flavor and single-angle approximation. The novel properties of collective neutrino oscillations are studied and distinct patterns of flavor and spin-flavor spectral splits are presented. Finally we also discuss how the neutrino magnetic moment affects the observable supernova neutrino energy spectra.
Neutrino flux streaming from a supernova can undergo rapid flavor conversions almost immediately above the core. Focusing on this region, we study these fast conversions using a linear stability analysis. We find that, for realistic angular distributions of neutrinos, fast conversions can occur within a few nanoseconds in regions just above the neutrinosphere. Our results also show that neutrinos travelling towards the core make fast conversions more rapid. These conversions, if they exist, can have significant implications for supernova explosion mechanism and nucleosynthesis.
Neutrinos propagating in dense neutrino media such as core-collapse supernovae and neutron star merger remnants can experience the so-called fast flavor conversions on scales much shorter than those expected in vacuum. A very generic class of fast flavor instabilities is the ones which are produced by the backward scattering of neutrinos off the nuclei at relatively large distances from the supernova core. In this study we demonstrate that despite their ubiquity, such fast instabilities are unlikely to cause significant flavor conversions if the population of neutrinos in the backward directio…
It has been recently pointed out that neutrino fluxes from a supernova can show substantial flavor conversions almost immediately above the core. Using linear stability analyses and numerical solutions of the fully nonlinear equations of motion, we perform a detailed study of these fast conversions, focussing on the region just above the supernova core. We carefully specify the instabilities for evolution in space or time, andfind that neutrinos travelling towards the core make fast conversions more generic, i.e., possible for a wider range of flux ratios and angular asymmetries that produce a…
In environments with high dense neutrino gases, such as in core-collapse supernovae, the neutrinos can experience collective neutrino oscillation due to their self-interactions. In particular, fast flavor conversion driven by the crossings in the neutrino angular distribution can affect explosion mechanism, nucleosynthesis, and neutrino observation. We perform the numerical computation of nonlinear flavor evolution on the neutrino angular distribution with tiny crossings expected to be generated in the preshock region. We demonstrate that the fast instability is triggered and a cascade develop…
Neutrinos in a core-collapse supernova can undergo fast flavor conversions with a possible impact on the explosion mechanism and nucleosynthesis. We perform the first non-linear simulations of fast conversions in the presence of three neutrino flavors. The recent supernova simulations with muon production call for such an analysis, as they relax the standard $ν_{μ,τ}=\barν_{μ,τ}$ (two-flavor) assumption. Our results show the significance of muon and tau lepton number angular distributions, together with the traditional electron lepton number ones. Indeed, our three-flavor results are potential…
We show that a self-interacting neutrino gas can spontaneously acquire a non-stationary pulsating component in its flavor content, with a frequency that can exactly cancel the "multi-angle" refractive effects of dense matter. This can then enable homogeneous and inhomogeneous flavor conversion instabilities to exist even at large neutrino and matter densities, where the system would have been stable if the evolution were strictly stationary. Large flavor conversions, especially close to a supernova core, are possible via this novel mechanism. This may have important consequences for the explos…
Self induced neutrino flavor conversions in the dense regions of stellar core collapse are almost exclusively studied in the standard two flavor scenario. Linear stability analysis has been successfully used to understand these flavor conversions. This is the first linearized study of $\textit{three flavor}$ fast instabilities. The `fast' conversions are fascinating distinctions of the dense neutrino systems. In the fast modes the collective oscillation dynamics are independent of the neutrino mass, growing at the scale of the large neutrino-neutrino interaction strength ($10^5$ km$^{-1}$) of …
Electron number densities in stars and the Earth are inhomogeneous because of atomic electrons. The large inhomogeneities on atomic-scale tend to form at tops of respective layers of stars, and 1s electrons of O locally produce weak potentials higher than that of the high MSW resonance. Then, supernova neutrinos experience vast numbers of non-adiabatic transitions. This inhomogeneous electron potential generates finite amplitudes of all three propagation eigenstates, and wave packets effectively separate. Then, spectral differences between three flavors significantly diminishes after propagati…
Axionlike-particles (ALPs) are one promising type of dark matter candidate particle that may generate detectable effects on $γ$-ray spectra other than the canonical weakly interacting massive particles. In this work we search for such oscillation effects in the spectra of supernova remnants caused by the photon-ALP conversion, using the Fermi Large Area Telescope data. Three bright supernova remnants, IC443, W44, and W51C, are analyzed. The inclusion of photon-ALP oscillations yields an improved fit to the $γ$-ray spectrum of IC443, which gives a statistical significance of $4.2σ$ in favor of …
Neutrino-neutrino interactions can lead to collective flavor conversion in the dense parts of a core collapse supernova. Growing instabilities that lead to collective conversions have been studied intensely in the limit of two-neutrino species and occur for inverted mass ordering in the case of a perfectly spherical supernova. We examine two simple models of colliding and intersecting neutrino beams and show, that for three neutrino species instabilities exist also for normal mass ordering even in the case of a fully symmetric system. Whereas the instability for inverted mass ordering is assoc…
A dense gas of neutrinos and antineutrinos can undergo fast pairwise conversions near the decoupling regions of core-collapse supernovae and in compact binary neutron star mergers. The flavor dependent neutrino heating can play a role in sustaining convection inside the hot and dense matter. In this paper, we study the unexplored effect of the bulk velocity of matter on fast pairwise conversions and demonstrate that depending on the direction and the magnitude of the bulk velocity, neutrino flavor conversions could be significantly enhanced or suppressed. The bulk velocity of matter, which is …
There is mounting evidence that neutrinos undergo fast flavor conversion (FFC) in core-collapse supernova (CCSN). In this letter, we investigate the roles of stellar rotation on the occurrence of FFC by carrying out axisymmetric CCSN simulations with full Boltzmann neutrino transport. Our result suggests that electron neutrino lepton number (ELN) angular crossings, which are the necessary and sufficient condition to trigger FFC, preferably occur in the equatorial region for rotating CCSNe. By scrutinizing the neutrino--matter interaction and neutrino radiation field, we find some pieces of evi…
In very dense environments, neutrinos can undergo fast flavor conversions on scales as short as a few centimeters provided that the angular distribution of the neutrino lepton number crosses zero. This work presents the first attempt to establish whether the non-negligible abundance of muons and their interactions with neutrinos in the core of supernovae can affect the occurrence of such crossings. For this purpose we employ state-of-the-art one-dimensional core-collapse supernova simulations, considering models that include muon-neutrino interactions as well as models without these reactions.…
Neutrinos emitted from a supernova may undergo flavor conversions almost immediately above the core, with possible consequences for supernova dynamics and nucleosynthesis. However, the precise conditions for such fast conversions can be difficult to compute and require knowledge of the full angular distribution of the flavor-dependent neutrino fluxes, that is not available in typical supernova simulations. In this paper, we show that the overall flavor evolution is qualitatively similar to the growth of a so-called `zero mode', determined by the background matter and neutrino densities, which …
We make a strong case that the fast neutrino-flavor conversion, one of the collective flavor oscillation modes, commonly occurs in core-collapse supernovae (CCSNe). It is confirmed in the numerical data obtained in realistic simulations of CCSNe but the argument is much more generic and applicable universally: the coherent neutrino-nucleus scattering makes the electron lepton number (ELN) change signs at some inward direction and trigger the flavor conversion in the outward direction in the pre-shock region. Although the ELN crossing is tiny and that is why it has eluded recognition so far, it…
Neutrinos propagating in dense neutrino media such as those in core-collapse supernovae can experience fast flavor conversions on scales much shorter than those expected in vacuum. It is believed that a necessary condition for the occurrence of fast modes is that the angular distributions of $ν_e$ and $\barν_e$ cross each other. However, most of the state-of-the-art supernova simulations do not provide such detailed angular information and instead, consider only a few moments of neutrino angular distributions. We here propose an efficient method to use these available few moments to search for…
Energy-dependent slow collective flavor conversion of supernova neutrinos
Institute of Physics, Academia Sinica（中央研究院物理研究所）；Institut für Astroteilchenphysik, Karlsruhe Institute of Technology (KIT)（卡尔斯鲁厄理工学院天体粒子物理研究所）；Department of Physics, University of California Berkeley（加州大学伯克利分校物理系）；Department of Physics, University of California San Diego（加州大学圣地亚哥分校物理系）；Institute of Astronomy and Astrophysics, Academia Sinica（中央研究院天文及物理学研究所）；Physics Division, National Center for Theoretical Sciences（国家理论科学中心物理组）；Max-Planck-Institut für Physik (Werner-Heisenberg-Institut)（马克斯·普朗克物理研究所（维尔纳·海森堡研究所））；GSI Helmholtzzentrum für Schwerionenforschung（GSI亥姆霍兹重离子研究中心）
Self-induced flavor conversion of supernova (SN) neutrinos is a generic feature of neutrino-neutrino dispersion. The corresponding run-away modes in flavor space can spontaneously break the original symmetries of the neutrino flux and in particular can spontaneously produce small-scale features as shown in recent schematic studies. However, the unavoidable "multi-angle matter effect" shifts these small-scale instabilities into regions of matter and neutrino density which are not encountered on the way out from a SN. The traditional modes which are uniform on the largest scales are most prone f…
Fast-pairwise collective neutrino oscillation represents a key uncertainty in the theory of core-collapse supernova (CCSN). Despite the potentially significant impact on CCSN dynamics, it is usually neglected in numerical models of CCSN because of the formidable technical difficulties of self-consistently incorporating this physics. In this paper, we investigate the prospects for the occurrence of fast flavor conversion by diagnosing electron neutrino lepton number (ELN) crossing in more than a dozen state-of-the-art three-dimensional CCSN models. ELN crossings is a necessary condition for tri…
The dense neutrino medium in a core-collapse supernova or a neutron-star merger event can experience fast flavor conversions on time/distance scales that are much smaller than those of vacuum oscillations. It is believed that fast neutrino flavor transformation occurs in the region where the angular distributions of $ν_e$ and $\barν_e$ cross each other. We present the first study of this crossing phenomenon and the fast neutrino flavor conversions in multidimensional (multi-D) supernova models. We examine the neutrino distributions obtained by solving the Boltzmann transport equation for sever…
We study the effects of non-standard self-interactions (NSSI) of neutrinos streaming out of a core-collapse supernova. We show that with NSSI, the standard linear stability analysis gives rise to linearly as well as exponentially growing solutions. For a two-box spectrum, we demonstrate analytically that flavor-preserving NSSI lead to a suppression of bipolar collective oscillations. In the intersecting four-beam model, we show that flavor-violating NSSI can lead to fast oscillations even when the angle between the neutrino and antineutrino beams is obtuse, which is forbidden in the Standard M…
Detailed dependence of resonant spin-flavor (RSF) conversion of supernova neutrinos on electron mole fraction Ye is investigated. Supernova explosion forms a hot-bubble and neutrino-driven wind region of which electron mole fraction exceeds 0.5 in several seconds after the core collapse. When a higher resonance of the RSF conversion is located in the innermost region, flavor change of the neutrinos strongly depends on the sign of 1-2Ye. At an adiabatic high RSF resonance the flavor conversion of bar{nu}_e -> nu_{mu,tau} occurs in Ye < 0.5 and normal mass hierarchy or in Ye > 0.5 and inverted m…
Magnetic Turbulence Boosts Supernova Signals of Axion-Photon Conversion
Istituto Nazionale di Fisica Nucleare (INFN)（意大利国家核物理研究所）；Gran Sasso Science Institute (GSSI)（格兰萨索科学研究所）；Università degli Studi di Padova（帕多瓦大学）；Max-Planck-Institut für Physik（马克斯·普朗克物理研究所）
We bring to light a novel mechanism through which turbulent matter density fluctuations can induce collective neutrino flavor conversions in core-collapse supernovae, i.e., the leakage of flavor instabilities between different Fourier modes. The leakage mechanism leaves its notable fingerprint on the flavor stability of a dense neutrino gas by coupling flavor conversion modes on different scales which in turn, makes the flavor instabilities almost ubiquitous in the Fourier space. The most remarkable consequence of this effect is in that it allows for the presence of significant flavor conversi…
Neutrinos play a key role in core-collapse supernova explosions. Carrying information from deep inside the stellar core, neutrinos are direct probes of the supernova mechanism. Intriguing recent developments on the role of neutrinos in supernovae are reviewed, as well as our current understanding of the flavor conversions in the stellar envelope, and the detection perspectives of the next burst.
Fast-pairwise neutrino oscillations potentially affect many aspects of core-collapse supernova (CCSN): the explosion mechanism, neutrino signals, and nucleosynthesis in the ejecta. This particular mode of collective neutrino oscillations has a deep connection to the angular structure of neutrinos in momentum space; for instance, the appearance of electron neutrinos lepton number (ELN) angular crossings in momentum space is a good indicator of occurrences of the flavor conversions. However, many multi-dimensional (multi-D) CCSN simulations are carried out with approximate neutrino transport (su…
We revisit our previous results on the matter suppression of self-induced neutrino flavor conversions during a supernova (SN) accretion phase, performing a linearized stability analysis of the neutrino equations of motion, in the presence of realistic SN density profiles. In our previous numerical study, we used a simplified model based on an isotropic neutrino emission with a single typical energy. Here, we take into account realistic neutrino energy and angle distributions. We find that multi-energy effects have a sub-leading impact in the flavor stability of the SN neutrino fluxes with resp…
We show that for the active-sterile flavor mixing parameters suggested by the reactor neutrino anomaly, substantial \ν_e-\ν_s and \bar \ν_e-\bar \ν_s conversion occurs in regions with electron fraction of \approx 1/3 near the core of an 8.8 M_sun electron-capture supernova. Compared to the case without such conversion, the neutron-richness of the ejected material 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. Active-sterile flavor conversion also strongly suppresses neutrino heating at times when it…
Supernova remnants (SNRs) can be rich sources of information on the parent SN explosion. Thus investigating the transition from the phase of SN to that of SNR can be crucial to link these two phases of evolution. Here we aim to study the early development of SNR in more details, paying the major attention to the transition from the early-expansion stage to the Sedov stage and the role played by magnetic field in this transition. To this end, spherical magneto-hydrodynamic simulations of SNRs have been performed to study the evolution of magnetic field in young SNRs and explore a sequence of th…
A surprising consequence of non-linear flavor evolution is the spontaneous breaking of the initial symmetries of the neutrino gas propagating in a dense astrophysical environment. We explore the flavor conversion physics by taking into account the polar and azimuthal angular distributions of neutrinos and present the very first example of spontaneous symmetry breaking in the context of fast flavor mixing in the nonlinear regime. Intriguingly, we find that fast flavor mixing does not always develop in the proximity of the angular regions with vanishing electron lepton number, as commonly assume…
We all know that in the dense anisotropic interior of the star, neutrino-neutrino forward-scattering can lead to fast collective neutrino oscillations, which has striking consequences on flavor dependent neutrino emission and can be crucial for the evolution of a supernova and its neutrino signal. The flavor evolution of such dense neutrino system is governed by a large number of coupled nonlinear partial differential equations which are almost always very difficult to solve. Although the triggering, initial linear growth and the condition for fast oscillations to occur are understood by "Line…
Fast neutrino-flavor conversion (FFC) is a possible game-changing ingredient in core-collapse supernova (CCSN) theory. In this paper, we examine the impact of FFC on explosive nucleosynthesis by including the effects of FFC in conjunction with asymmetric neutrino emission into nucleosynthetic computations in a parametric way. We find that the ejecta compositions are not appreciably affected by FFC for elements lighter than Co, while the compositions are influenced by FFC for the heavier elements. We also find that the role of FFC varies depending on the asymmetric degree of neutrino emission (…
Intermittent Turbulence, Fast Flavor Conversion, and Observable Supernova Probes
Tsung-Dao Lee Institute, Shanghai Jiao Tong University（上海交大李政道研究所）；School of Physics and Astronomy, Shanghai Jiao Tong University（上海交通大学物理与天文学院）；Center for Theoretical Physics, College of Physics Science and Technology, Sichuan University（四川大学物理科学与技术学院理论物理中心）；Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati（意大利国家核物理研究所弗拉斯卡蒂国家实验室）
Application of interpretable data-driven methods for the reconstruction of supernova neutrino energy spectra following fast neutrino flavor conversions
School of Physical Science and Technology, Xinjiang University（新疆大学物理科学与技术学院）；Xinjiang Astronomical Observatory, Chinese Academy of Sciences（中国科学院新疆天文台）；School of Astronomy and Space Science, University of Chinese Academy of Sciences（中国科学院大学天文与空间科学学院）；International Centre of Supernovae, Yunnan Key Laboratory of Supernova Research, Yunnan Observatories, Chinese Academy of Sciences（中国科学院云南天文台超新星国际研究中心、云南省超新星研究重点实验室）；Key Laboratory for Structure and Evolution of Celestial Objects, Chinese Academy of Sciences（中国科学院天体结构与演化重点实验室）；Guangxi Key Laboratory for Relativistic Astrophysics, School of Physical Science and Technology, Guangxi University（广西大学物理科学与技术学院相对论天体物理重点实验室）
The flavor conversion of a neutrino usually occurs at densities $\lesssim G_F^{-1} ω$, whether in the ordinary matter or the neutrino medium, and on time/distance scales of order $ω^{-1}$, where $G_F$ is the Fermi weak coupling constant and $ω$ is the vacuum oscillation frequency of the neutrino. In 2005 Sawyer and more recently both he and other groups have shown that neutrino flavor conversions can occur on scales much shorter than $ω^{-1}$ in a very dense, anisotropic neutrino gas such as that in a core-collapse supernova or a binary neutron star merger. It has also been suggested that the …
Neutrino fast pairwise conversions have been postulated to occur in the dense core of a core-collapse supernova (SN), possibly having dramatic consequences on the SN mechanism and the observable neutrino signal. One crucial condition favoring pairwise conversions is the presence of crossings between the electron neutrino and antineutrino angular distributions (i.e., electron neutrino lepton number crossings, ELN crossings). A stationary and spherically symmetric SN toy-model is constructed to reproduce the development of the neutrino angular distributions in the dense SN core in the absence of…
Neutrinos are densely populated deep inside the core of massive stars after their gravitational collapse to produce supernova explosions and form compact stars such as neutron stars (NS) and black holes (BH). It has been considered that they may change their flavor identities through so-called fast-pairwise conversions induced by mutual forward scatterings. If that is really the case, the dynamics of supernova explosion will be influenced, since the conversion may occur near the neutrino sphere, from which neutrinos are effectively emitted. In this paper, we conduct a pilot study of such possi…
Role of Matter Inhomogeneity on Fast Flavor Conversion of Supernova Neutrinos
Institute of Physics, Academia Sinica（中央研究院物理研究所）；Institute of Astronomy and Astrophysics, Academia Sinica（中央研究院天文及物理学研究所）；National Center for Theoretical Sciences（国家理论科学中心）；GSI Helmholtzzentrum für Schwerionenforschung（德国重离子研究中心）
