Neutrinos in a core-collapse supernova undergo coherent flavor transformations in their own background. We explore this phenomenon during the cooling stage of the explosion. Our three-flavor ...calculations reveal qualitatively new effects compared to a two-flavor analysis. These effects are especially clearly seen for the inverted mass hierarchy: we find a different pattern of spectral "swaps" in the neutrino spectrum and a novel "mixed" spectrum for the antineutrinos. A brief discussion of the relevant physics is presented, including the instability of the two-flavor evolution trajectory, the three-flavor pattern of spectral "swaps," and partial nonadiabaticity of the evolution.
We demonstrate that the neutrino-driven outflows inside exploding core-collapse supernovae possess a special property of near-criticality, that is, they are on the edge of forming termination shocks. ...We derive a novel criterion for the formation of the shock, in terms of the fundamental parameters of the problem: the neutrino luminosity and energy as well as the properties of the protoneutron star. The criterion provides a unified description of the available numerical results and motivates future simulations. The property of near-criticality makes the neutrino signatures of the termination shocks a sensitive diagnostic of the physical conditions around the PNS several seconds into the explosion. The expected signal at DUNE is found to be statistically significant.
We investigate collective flavor oscillations of supernova neutrinos at late stages of the explosion. We first show that the frequently used single-angle (averaged coupling) approximation predicts ...oscillations close to, or perhaps even inside, the neutrinosphere, potentially invalidating the basic neutrino transport paradigm. Fortunately, we also find that the single-angle approximation breaks down in this regime; in the full multiangle calculation, the oscillations start safely outside the transport region. The new suppression effect is traced to the interplay between the dispersion in the neutrino-neutrino interactions and the vacuum oscillation term.
We argue that the small fraction of neutrinos that undergo direction-changing scattering outside of the neutrinosphere could have significant influence on neutrino flavor transformation in ...core-collapse supernova environments. We show that the standard treatment for collective neutrino flavor transformation is adequate at late times but could be inadequate in early epochs of core-collapse supernovae, where the potentials that govern neutrino flavor evolution are affected by the scattered neutrinos. Taking account of this effect, and the way it couples to entropy and composition, will require a new approach in neutrino flavor transformation modeling.
Available estimates for the energy resolution of DUNE vary by as much as a factor of 4. To address this controversy, and to connect the resolution to the underlying physical processes, we build an ...independent simulation pipeline for neutrino events in liquid argon, combining the public tools genie and fluka. Using this pipeline, we first characterize the channels of nonhermeticity of DUNE, including subthreshold particles, charge recombination, and nuclear breakup. Particular attention is paid to the role of neutrons, which are responsible for a large fraction of missing energy in all channels. Next, we determine energy resolution, by quantifying event-to-event stochastic fluctuations in missing energy. This is done for several sets of assumptions about the reconstruction performance, including those available in the literature. The resulting migration matrices, connecting true and reconstructed neutrino energies, are presented. Finally, we quantify the impact of different improvements on the experimental performance. For example, we show that dropping particle identification information degrades the resolution by a factor of 2, while omitting charge deposits from deexcitation gammas worsens it by about 25%. In the future, this framework can be used to assess the impact of cross section uncertainties on the oscillation sensitivity.
Thorough modeling of the physics involved in liquid argon calorimetry is essential for accurately predicting the performance of DUNE and optimizing its design and analysis pipeline. At the ...fundamental level, it is essential to quantify the detector response to individual hadrons-protons, charged pions, and neutrons-at different injection energies. We report such a simulation, analyzed under different assumptions about event reconstruction, such as particle identification and neutron detection. The role of event containment is also quantified. The results of this simulation can help inform the ProtoDUNE test-beam data analysis, while also providing a framework for assessing the impact of various cross section uncertainties.
We point out that stars in the mass window ~8-12M(circumpunct) can serve as sensitive probes of the axion-photon interaction, g(Aγγ). Specifically, for these stars axion energy losses from the ...helium-burning core would shorten and eventually eliminate the blue loop phase of the evolution. This would contradict observational data, since the blue loops are required, e.g., to account for the existence of Cepheid stars. Using the MESA stellar evolution code, modified to include the extra cooling, we conservatively find g(Aγγ)</~0.8×10(-10) GeV(-1), which compares favorably with the existing bounds.
We investigate whether coherent flavor conversion of neutrinos in a neutrino background is substantially modified by many-body effects, with respect to the conventional one-particle effective ...description. We study the evolution of a system of interacting neutrino plane waves in a box. Using its equivalence to a system of spins, we determine the character of its behavior completely analytically. We find that, if the neutrinos are initially in flavor eigenstates, no coherent flavor conversion is realized, in agreement with the effective one-particle description. This result does not depend on the size of the neutrino wavepackets and therefore has a general character. The validity of the several important applications of the one-particle formalism is thus confirmed.
Results of neutrino oscillation experiments have always been presented on the (sin
22
θ,
Δm
2) parameter space for the case of two-flavor oscillations. We point out, however, that this ...parameterization misses the half of the parameter space
π
4
<θ≤
π
2
(`the dark side'), which is physically inequivalent to the region
0≤θ≤
π
4
(`the light side') in the presence of matter effects. The MSW solutions to the solar neutrino problem can extend to the dark side, especially if we take the conservative attitude to allow higher confidence levels, ignore some of the experimental results in the fits, or relax theoretical predictions. Furthermore, even the so-called `vacuum oscillation' solution distinguishes the dark and the light sides. We urge experimental collaborations to present their results on the entire parameter space.
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