Scalar nonstandard neutrino interactions in galactic supernovae

summary

The gist

The gist: Supernova neutrinos provide an exceptional environment to probe scalar nonstandard interactions, leveraging their unique features to resolve sharp time features of the neutronization burst.

In short

Supernova neutrinos are used to search for scalar nonstandard interactions (SNSI) by observing changes in the neutronization burst signal. SNSI modifies how neutrinos change flavor in dense supernova environments, creating a density-squared effect on mass differences. This unique environment allows probes of SNSI parameters up to four orders of magnitude better than terrestrial sources, potentially revealing new physics at experiments like DUNE.

Key concepts

Scalar Nonstandard Interactions (SNSI): This refers to a hypothetical new particle ($\phi$) that mediates interactions between neutrinos and fermions. This interaction modifies the neutrino mass differences in dense media, leading to flavor conversion probabilities that differ from the Standard Model predictions.
Neutronization Burst: This is the initial, very short phase of neutrino emission during a supernova core collapse. It is characterized by an intense peak in electron neutrino ($\nu_e$) luminosity and serves as a sharp temporal feature that can be altered by new physics like SNSI.
Density-Squared Dependence: In the extremely dense environment inside a supernova, SNSI introduces a contribution to neutrino mass-squared differences that scales with the square of the local matter density. This effect is absent in less dense places like Earth or the Sun, making supernovae ideal for testing these specific interactions.

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This episode discusses

The paper

Scalar nonstandard neutrino interactions in galactic supernovae · Read on arXiv

Bhaskar Dutta, *Aparajitha Karthikeyan †Nityasa Mishra ‡Yago Porto § Louis E. Strigari

Department of Physics and Astronomy, Mitchell Institute for Fundamental Physics and Astronomy, Texas A&M University · Centro de Ciências Naturais e Humanas, Universidade Federal do ABC · Instituto de Física Gleb Wataghin, Universidade Estadual de Campinas

We analyze the prospects for studying scalar nonstandard interactions (SNSI) using the neutrino burst from a galactic supernova (SN). SNSI modifies the resonant flavor conversion and, correspondingly, the neutronization burst signal, and may be identifiable in future multi-tonne-scale experiments, such as Deep Underground Neutrino Experiment (DUNE). Notably, in the normal mass ordering, SNSI can lead to an anomalous (re)appearance of the neutronization-burst ν e peak at Earth, a feature otherwise strongly suppressed in the Standard Model. We show that, in the presence of SNSI, neutrinos propagating out of the dense SN environment acquire a density-squared-dependent contribution to their mass-squared differences, which in turn modifies the energy levels of the neutrino matter eigenstates. This density-squared effect is absent in less dense environments such as the Earth or the Sun and is precisely what enables SN neutrinos to probe SNSI parameters up to 4 orders of magnitude below the values accessible to solar or terrestrial neutrino sources.

DOI: 10.1103/lgkg-tf2y

Transcript

Introduction to the show: ident: Astrophysics Radio. Generated commentary on the latest astrophysics papers.

Vera: Today's paper: "Scalar nonstandard neutrino interactions in galactic supernovae".

Jocelyn: The gist: Supernova neutrinos provide an exceptional environment to probe scalar nonstandard interactions, leveraging their unique features to resolve sharp time features of the neutronization burst.

Vera: First, who's behind it and why it matters.

Title and authors: Vera: Moving on to the actual summary of this paper, "Scalar nonstandard neutrino interactions in galactic supernovae," they lay out how the standard physics picture gets tweaked when you introduce these scalar interactions. Basically, they look at how the flavor conversion probabilities are modified when neutrinos pass through a very dense medium during that initial neutronization burst phase.

Jocelyn: And what they emphasize is that this modification isn't just a small correction; it fundamentally changes the way the neutrino evolution happens inside the supernova compared to standard matter effects. They focus on those resonant flavor conversions, specifically mentioning the H-resonance and L-resonance concepts.

Subrahmanyan: The paper points out that in a normal ordering scenario, this interaction can cause an initial electron neutrino flux to transform into a pure nu three flux by the time it gets to Earth, which is a key prediction for how we’d see the signal <ref:2508.16558#pg1>.

Vera: And they show that if these scalar interactions are present, they can significantly alter the expected flavor evolution during that critical neutronization burst phase. They use hydrodynamical simulations to show exactly what happens at different postbounce times.

Jocelyn: The simulations they present, like the ones for a twelve solar mass progenitor, help illustrate how those specific flavor transitions manifest in terms of luminosity and energy spectra right when the burst is happening <ref:2508.16558#pg3>.

Subrahmanyan: It’s important to remember that this work also considers constraints on these interactions by requiring that any induced neutrino masses within the core stay below the expected emission temperatures, which keeps things physically sensible.

The paper's summary: Vera: Now, let's talk about what the authors actually suggest as improvements to their initial ideas in this paper. They introduce new ways to analyze these interactions by looking at a modified evolution Hamiltonian that includes these nonstandard terms.

Jocelyn: They are essentially proposing a way to map out the entire parameter space by analyzing how those additional terms in the Hamiltonian rearrange the energy levels of the neutrino mass eigenstates. It helps them see if they can generate entirely new matter resonances, not just tweak the old ones.

Subrahmanyan: This is crucial because it allows for a much deeper look at whether these scalar interactions can actually produce qualitatively different oscillation behavior than what we expect from standard physics. They are testing the boundaries of what’s possible in that extreme environment.

Vera: And they highlight that this method gives us a way to potentially distinguish scalar nonstandard interactions from other types of new physics, like vector-mediated NSI, because their scaling with density is different.

Jocelyn: They explain that vector NSI scales linearly with the local density, whereas scalar interactions scale quadratically with density in this supernova context; that difference is a major way they separate the physics here.

Subrahmanyan: That quadratic scaling is what makes the supernova so special for testing these specific types of interactions; it’s not something you find in less dense environments like the Earth or the Sun, which strengthens their case.

The paper's improvements: Vera: So, wrapping up this discussion on "Scalar nonstandard neutrino interactions in galactic supernovae," the main conclusion is that these supernova neutrinos offer an exceptional environment to probe scalar nonstandard interactions involving only non-electron flavors down to a value of ten-four.

Jocelyn: That's a very sensitive limit they set, and it really shows how important the next nearby supernova is as a natural lab for physics beyond the Standard Model. They suggest that if we see a signal, it could be one of these scalar interactions.

Subrahmanyan: The quadratic scaling of SNSI with density makes this environment particularly suitable for testing them; it gives us a unique signature that other sources can't provide. Even if we don't find anything in the next one, this paper sets a very clear benchmark for what we should look for in future multi-tonne-scale experiments like DUNE.

Vera: And looking ahead, the work suggests that DUNE could potentially be sensitive to these interactions down to values around ten-four assuming certain constraints on the neutrino masses are met. It’s a big step for our ability to constrain these new physics models.

Jocelyn: We're definitely keeping an eye on this area, because understanding how this paper predicts the flavor evolution during that neutronization burst is what drives our search for these nonstandard effects in astrophysical events. (No further speakers)

Conclusion: Vera: So we’ve been looking at how these scalar nonstandard neutrino interactions in galactic supernovae modify that initial neutronization burst signal, and what the implications are for our search for new physics in the sky.

Jocelyn: It really boils down to how these interactions change the flavor evolution when neutrinos are passing through that incredibly dense core, making it a much better probe than we had before.

Subrahmanyan: The authors show that this quadratic dependence of the scalar interaction on density is what makes this environment so special for testing these specific types of new physics.

Vera: Exactly, and they demonstrate how this allows us to get a four orders of magnitude sensitivity on SNSI parameters compared to what we’d see from solar or terrestrial sources.

Jocelyn: And they point out that if you look at the DUNE experiment, these modifications can actually make that neutronization peak visible in a way that's totally different from the standard picture.

Subrahmanyan: If propagation stays adiabatic, we expect to see an incoherent flux of nu two arriving at Earth instead of just pure nu three which is a key difference.

Vera: It’s interesting because it means we might be able to distinguish between different types of new physics, like scalar versus vector interactions, based on how they scale with density.

Jocelyn: And the paper mentions that even if propagation isn't fully adiabatic, there's still a way to tell the difference between the SNSI scenario and the standard MSW prediction by looking at those energy signals.

Subrahmanyan: That is the crucial part—that intermediate behavior in flavor composition could be a real signature we need to look for.

Vera: It’s compelling because it means that even if we don't see a massive deviation, there's still some potential for these interactions to leave a trace.

Jocelyn: So, the title "Scalar nonstandard neutrino interactions in galactic supernovae" really sums up what they did: using the supernova as a natural laboratory for BSM physics.

Subrahmanyan: It’s about setting a strong benchmark for how we can use astrophysical data to constrain these fundamental new interactions in particle physics.

Vera: We’ve got some great work here on these neutrino signals, and I'm looking forward to seeing what the next paper brings to the table.

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