We consider the effect of non-standard neutrino interactions (NSI, for short) on the propagation of neutrinos through the supernova (SN) envelope within a three-neutrino framework and taking into account the presence of a neutrino background. We find that for given NSI parameters, with strength generically denoted by $\varepsilon_{ij}$, neutrino evolution exhibits a significant time dependence. For $|\varepsilon_{ττ}|\gtrsim$ $10^{-3}$ the neutrino survival probability may become sensitive to the $θ_{23}$ octant and the sign of $\varepsilon_{ττ}$. In particular, if $\varepsilon_{ττ}\gtrsim 10^{-2}$ an internal $I$-resonance may arise independently of the matter density. For typical values found in SN simulations this takes place in the same dense-neutrino region above the neutrinosphere where collective effects occur, in particular during the synchronization regime. This resonance may lead to an exchange of the neutrino fluxes entering the bipolar regime. The main consequences are (i) bipolar conversion taking place for normal neutrino mass hierarchy and (ii) a transformation of the flux of low-energy $ν_e$, instead of the usual spectral swap.
In supernovae neutrinos are emitted from a region with a width $r_{\rm eff}$ of a few kilometers (rather than from a surface of infinitesimal width). We study the effect of integration (averaging) over such an extended emission region on collective oscillations. The averaging leads to additional suppression of the correlation (off-diagonal element of the density matrix) by a factor $ \sim 1/r_{\rm eff} V_e \sim 10^{-10}$, where $V_e$ is the matter potential. This factor enters the initial condition for further collective oscillations and, consequently, leads to a delay of the strong flavour tr…
We investigate the collective neutrino oscillations under the three flavor multi-angle approximation in a spherically symmetric simulation of failed supernovae. A failed supernova emits high neutrino fluxes in a short time, while intense accretion proceeds with high electron density enough to experience re-collapse into a black hole. Our results show that matter-induced effects completely dominate over neutrino self-interaction effects and multi-angle matter suppression occurs at all time snapshots we studied. These facts suggest us that only MSW resonances affect the neutrino flavor conversio…
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…
Mu-tau neutrino refraction and collective three-flavor transformations in supernovae
本文研究了超新星核心中微子球上方稠密中微子区的三味集体中微子变换。我们发现，两个味道转换驱动的大气质量差和13混合角捕获的全部效果，如果忽略μ介子和τ中微子折射率之间的二阶差。包括这个“μ-τ物质项”后，在密度约为3 x 10^7 g cm^-3时产生共振，这通常会导致电子中微子和反中微子的总体存活概率发生显著变化。这种效应令人惊讶地对最大23-混合的偏差敏感，对于每个八分圆是不同的。
Solar-System Abundances of $p$-Nuclides Probe Collective Neutrino Oscillations in Supernovae
SLAC National Accelerator Laboratory, Stanford University（斯坦福大学斯坦福直线加速器中心）；Leinweber Institute for Theoretical Physics, Stanford University（斯坦福大学莱因韦伯理论物理研究所）；Department of Physics, University of California Berkeley（加州大学伯克利分校物理系）；Department of Applied Mathematics and Theoretical Physics, University of Cambridge（剑桥大学应用数学与理论物理系）；Department of Physics, University of California San Diego（加州大学圣地亚哥分校物理系）；School of Physics and Astronomy, University of Minnesota（明尼苏达大学物理与天文学院）；Department of Physics, New York Institute of Technology（纽约理工学院物理系）；Reed College（里德学院）
We extend the multi-angle computational framework and investigate the time evolution of the neutrino halo on collective neutrino oscillation in the core collapse of an iron core progenitor. We find that in the case of the $9.6\, \rm M_\odot$ progenitor adopted in this work, there are windows of time when the effects of neutrino halo and collective neutrino oscillation are not simultaneously large. Inside the shock, the impact of the inward-scattered halo neutrino cannot in general be neglected compared to the outward-propagating neutrino flux. However, during early epochs, collective neutrino …
Neutrino self-interactions are known to lead to non-linear collective flavor oscillations in a core-collapse supernova. We point out new possible effects of non-standard self-interactions (NSSI) of neutrinos on flavor conversions in a two-flavor framework. We show that, for a single-energy neutrino-antineutrino ensemble, a flavor instability is generated even in normal hierarchy for large enough NSSI. Using a toy model for the neutrino spectra, we show that flavor-preserving NSSI lead to pinching of spectral swaps, while flavor-violating NSSI cause swaps to develop away from a spectral crossin…
In order to investigate the impact of collective neutrino oscillations (CNO) on the neutrino signal from a nearby supernova, we perform 3-flavor neutrino oscillation simulations employing the multiangle effect. The background hydrodynamic model is based on the neutrino hydrodynamic simulation of a 8.8 \Msun progenitor star. We find that CNO commences after some 100 ms post bounce. Before this, CNO is suppressed by matter-induced decoherence. In the inverted mass hierarchy, the spectrum of $\barν_e$ becomes softer after the onset of CNO. To evaluate the detectability of this modification, we de…
Recent theoretical work indicates that the neutrino radiation in core-collapse supernovae may be susceptible to flavor instabilities that set in far behind the shock, grow extremely rapidly, and have the potential to profoundly affect supernova dynamics and composition. Here we analyze the nonlinear collective oscillations that are prefigured by these instabilities. We demonstrate that a zero-crossing in $n_{ν_e} - n_{\barν_e}$ as a function of propagation angle is not sufficient to generate instability. Our analysis accounts for this fact and allows us to formulate complementary criteria. Usi…
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…
We study two-flavor neutrino oscillations in a homogeneous and isotropic ensemble under the influence of neutrino-neutrino interactions. For any density there exist forms of collective oscillations that show self-maintained coherence. They can be classified by a number N of linearly independent functions that describe all neutrino modes as linear superpositions. What is more, the dynamics is equivalent to another ensemble with the same effective density, consisting of N modes with discrete energies E_i with i=1, ..., N. We use this equivalence to derive the analytic solution for two-mode (bimo…
Neutrino flavor evolution in core-collapse supernovae, neutron-star mergers, or the early universe is dominated by neutrino-neutrino refraction, often spawning "self-induced flavor conversion", i.e., shuffling of flavor among momentum modes. This effect is driven by collective run-away modes of the coupled "flavor oscillators" and can spontaneously break the initial symmetries such as axial symmetry, homogeneity, isotropy, and even stationarity. Moreover, the growth rates of unstable modes can be of the order of the neutrino-neutrino interaction energy instead of the much smaller vacuum oscill…
After considering the supernova shock effects, the Mikheyev-Smirnov-Wolfenstein effects, the neutrino collective effects, and the Earth matter effects, the detection of supernova neutrinos at China Spallation Neutron Sources is studied and the event numbers of different flavor supernova neutrinos observed through various reaction channels are calculated with the neutrino energy spectra described by the Fermi-Dirac distribution and "beta fit" distribution respectively. Furthermore, the numerical calculation method of supernova neutrino detection on the Earth is applied to some other spallation …
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.
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）
