Abstract

Neutrino leptonic flavor symmetry violation is the only evidence for physics beyond the standard model. Much of what we have learned on these particles is derived from the study of their natural sources, such as the Sun or core-collapse supernovae. Neutrino emission from supernovae is particularly interesting and leptonic flavor transformations in supernova neutrinos have attracted a lot of theoretical attention. Unfortunately, the emission of core-collapse supernovae is not fully understood: thus, an inescapable preliminary step to progress is to improve on that, and future neutrino observations can help. One pressing and answerable question concerns the time distribution of the supernova anti-neutrino events. We propose a class of models of the time distribution that describe emission curves similar to those theoretically expected and consistent with available observations from the data of supernova SN1987A. They have the advantages of being motivated on physical bases and easy to interpret; they are flexible and adaptable to the results of the observations from a future galactic supernova. Important general characteristics of these models are the presence of an initial ramp and that a significant portion of the signal is in the first second of the emission.

Highlights

  • Neutrino leptonic flavor symmetry violation is the only evidence for physics beyond the standard model

  • Much of what we have learned about neutrinos comes from studying natural sources, such as those recognized by the 2002 Nobel Prize in Physics: The Sun and core-collapse supernovae

  • Decades-long discussion about their internal mechanism has made it clear that a specific kind of supernova occurs as a result of a gravitational collapse, which leads to the formation of compact stellar remnants accompanied by a brief and very intense neutrino emission [9,10,11,12,13,14,15,16,17,18,19,20,21,22], and likely by a burst of gravitational waves [23,24,25,26,27,28]

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Summary

Open Issues after Supernova 1987A

The first supernova observed in 1987 (SN1987A) is currently the only occasion when we have been able to directly verify our ideas about the chain of events that occur at key moments in the gravitational collapse. A minimal interpretation is corroborated: that a neutrino emission due to a gravitational collapse, not too different from the standard one, was observed, followed by the explosion of a supernova and the formation of a compact star In this light, it is interesting to consider the point originally made by Loredo and Lamb [42], and confirmed by an independent analysis by Pagliaroli, Vissani, Costantini and Ianni [43]: the interpretation of the time series data suggests that there was an initial phase of very high luminosity (see Section 5.2).

Parameterized Spectrum of Electronic Antineutrinos
Generalities
Model with Two Emission Phases
Emission from Processes around the Accretion Zone
Expectations
Remark on Neutrino Flavor Transformation
A Model for the Time Evolution
Description of Luminosity
Description of the Flux
Tests and Applications
Illustration of the Expected Flux
Comparison with SN1987A
Predictions
Variants and Possible Improvements
Variants Concerning the Cooling Component
Variants Concerning the Accretion Component
Variants Concerning the Other Neutrino Flavors
Discussion and Outlook
Findings
10 MeV 10 MeV
Full Text
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