arXiv subjects

Damiano F. G. Fiorillo

Publications and source records attributed to Damiano F. G. Fiorillo.

At least 73 records · Page 4Linked to original sources

arXiv2024

Large Neutrino Secret Interactions, Small Impact on Supernovae

When hypothetical neutrino secret interactions ($ν$SI) are large, they form a fluid in a supernova (SN) core, flow out with sonic speed, and stream away as a fireball. For the first time, we tackle the complete dynamical problem and solve all steps, systematically using relativistic hydrodynamics. The impact on SN physics and the neutrino signal is remarkably small. For complete thermalization within the fireball, the observable spectrum changes in a way that is independent of the coupling strength. One potentially large effect beyond our study is quick deleptonization if $ν$SI violate lepton number. By present evidence, however, SN physics leaves open a large region in parameter space, where laboratory searches and future high-energy neutrino telescopes will probe $ν$SI.

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arXiv2024

Collective neutrino-antineutrino oscillations in dense neutrino environments?

The paradigm-changing possibility of collective neutrino-antineutrino oscillations was recently advanced in analogy to collective flavor oscillations. However, the amplitude for the backward scattering process $ν_{\mathbf{p}_1}\overlineν_{\mathbf{p}_2}\toν_{\mathbf{p}_2}\overlineν_{\mathbf{p}_1}$ is helicity-suppressed and vanishes for massless neutrinos, implying that there is no off-diagonal refractive index between $ν$ and $\overlineν$ of a single flavor of massless neutrinos. For a nonvanishing mass, collective helicity oscillations are possible, representing de-facto $ν$--$\overlineν$ oscillations in the Majorana case. However, such phenomena are suppressed by the smallness of neutrino masses as discussed in the previous literature.

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arXiv2023

Searches for dark matter decay with ultra-high-energy neutrinos endure backgrounds

Next-generation ultra-high-energy (UHE) neutrino telescopes, presently under planning, will have the potential to probe the decay of heavy dark matter (DM) into UHE neutrinos, with energies in excess of $10^7$~GeV. Yet, this potential may be deteriorated by the presence of an unknown background of UHE neutrinos, cosmogenic or from astrophysical sources, not of DM origin and seemingly large enough to obscure the DM signature. We show that leveraging the angular and energy distributions of detected events safeguards future searches for DM decay against such backgrounds. We focus on the radio-detection of UHE neutrinos in the planned IceCube-Gen2 neutrino telescope, which we model in state-of-the-art detail. We report promising prospects for the discovery potential of DM decay into UHE neutrinos, the measurement of DM mass and lifetime, and limits on the DM lifetime, despite the presence of a large background, without prior knowledge of its size and shape.

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arXiv2023

Identifying Energy-Dependent Flavor Transitions in High-Energy Astrophysical Neutrino Measurements

The flavor composition of TeV--PeV astrophysical neutrinos, i.e., the proportion of neutrinos of different flavors in their flux, is a versatile probe of high-energy astrophysics and fundamental physics. Because flavor identification is challenging and the number of detected high-energy astrophysical neutrinos is limited, so far measurements of the flavor composition have represented an average over the range of observed neutrino energies. Yet, this washes out the potential existence of changes in the flavor composition with energy and weakens our sensitivity to the many models that posit them. For the first time, we measure the energy dependence of the flavor composition, looking for a transition from low to high energies. Our present-day measurements, based on the 7.5-year public sample of IceCube High-Energy Starting Events (HESE), find no evidence of a flavor transition. The observation of HESE and through-going muons jointly by next-generation neutrino telescopes Baikal-GVD, IceCube-Gen2, KM3NeT, P-ONE, TAMBO, and TRIDENT may identify a flavor transition around 200TeV by 2030. By 2040, we could infer the flavor composition with which neutrinos are produced with enough precision to establish the transition from neutrino production via the full pion decay chain at low energies to muon-damped pion decay at high energies.

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arXiv2023

Supernova Simulations Confront SN 1987A Neutrinos

We return to interpreting the historical SN~1987A neutrino data from a modern perspective. To this end, we construct a suite of spherically symmetric supernova models with the Prometheus-Vertex code, using four different equations of state and five choices of final baryonic neutron-star (NS) mass in the 1.36-1.93 M$_\odot$ range. Our models include muons and proto-neutron star (PNS) convection by a mixing-length approximation. The time-integrated signals of our 1.44 M$_\odot$ models agree reasonably well with the combined data of the four relevant experiments, IMB, Kam-II, BUST, and LSD, but the high-threshold IMB detector alone favors a NS mass of 1.7-1.8 M$_\odot$, whereas Kam-II alone prefers a mass around 1.4 M$_\odot$. The cumulative energy distributions in these two detectors are well matched by models for such NS masses, and the previous tension between predicted mean neutrino energies and the combined measurements is gone, with and without flavor swap. Generally, our predicted signals do not strongly depend on assumptions about flavor mixing, because the PNS flux spectra depend only weakly on antineutrino flavor. While our models show compatibility with the events detected during the first seconds, PNS convection and nucleon correlations in the neutrino opacities lead to short PNS cooling times of 5-9 s, in conflict with the late event bunches in Kam-II and BUST after 8-9 s, which are also difficult to explain by background. Speculative interpretations include the onset of fallback of transiently ejected material onto the NS, a late phase transition in the nuclear medium, e.g., from hadronic to quark matter, or other effects that add to the standard PNS cooling emission and either stretch the signal or provide a late source of energy. More research, including systematic 3D simulations, is needed to assess these open issues.

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arXiv2023

Starburst Nuclei as Light Dark Matter Laboratories

Starburst galaxies are well-motivated astrophysical emitters of high-energy gamma-rays. They are well-known cosmic-ray "reservoirs", thanks to their large magnetic fields which confine high-energy protons for $\sim 10^5$ years. Over such long times, cosmic-ray transport can be significantly affected by scatterings with sub-GeV dark matter. Here we point out that this scattering distorts the cosmic-ray spectrum, and the distortion can be indirectly observed by measuring the gamma-rays produced by cosmic-rays via hadronic collisions. Present gamma-ray data show no sign of such a distortion, leading to stringent bounds on the cross section between protons and dark matter. These are highly complementary with current bounds and have large room for improvement with the future gamma-ray measurements in the 0.1-10 TeV range from the Cherenkov Telescope Array, which can strengthen the limits by as much as two orders of magnitude.

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arXiv2023

Hunting for bumps in the diffuse high-energy neutrino flux

The origin of the TeV--PeV astrophysical neutrinos seen by the IceCube telescope is unknown. If they are made in proton-photon interactions in astrophysical sources, their spectrum may show bump-like features. We search for such features in the 7.5-years High-Energy Starting Events (HESE), and forecast the power of such searches using larger data samples expected from upcoming telescopes. Present-day data reveals no evidence of bump-like features, which allows us to constrain candidate populations of photohadronic neutrino sources. Near-future forecasts show promising potential for stringent constraints or decisive discovery of bump-like features. Our results provide new insight into the origins of high-energy astrophysical neutrinos, complementing those from point-source searches.

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arXiv2023

Strong Supernova 1987A Constraints on Bosons Decaying to Neutrinos

Majoron-like bosons would emerge from a supernova (SN) core by neutrino coalescence of the form $νν\toϕ$ and $\barν\barν\toϕ$ with 100 MeV-range energies. Subsequent decays to (anti)neutrinos of all flavors provide a flux component with energies much larger than the usual flux from the "neutrino sphere." The absence of 100 MeV-range events in the Kamiokande-II and Irvine-Michigan-Brookhaven signal of SN 1987A implies that less than 1% of the total energy was thus emitted and provides the strongest constraint on the Majoron-neutrino coupling of $g\lesssim 10^{-9}\,{\rm MeV}/m_ϕ$ for $100~{\rm eV}\lesssim m_ϕ\lesssim 100~{\rm MeV}$. It is straightforward to extend our new argument to other hypothetical feebly interacting particles.

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arXiv2023

Axion-sourced fireballs from supernovae

New feebly interacting particles would emerge from a supernova core with 100-MeV-range energies and produce $γ$-rays by subsequent decays. These would contribute to the diffuse cosmic $γ$-ray background or would have shown up in the Solar Maximum Mission (SMM) satellite from SN~1987A. However, we show for the example of axion-like particles (ALPs) that, even at distances beyond the progenitor star, the decay photons may not escape, and can instead form a fireball, a plasma shell with $T\lesssim 1$ MeV. Thus, existing arguments do not exclude ALPs with few 10 MeV masses and a two-photon coupling of a few $10^{-10}~{\rm GeV}^{-1}$. However, the energy would have showed up in sub-MeV photons, which were not seen from SN 1987A in the Pioneer Venus Orbiter (PVO), closing again this new window. A careful re-assessment is required for other particles that were constrained in similar ways.

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arXiv2023

Heavy decaying dark matter at future neutrino radio telescopes

In the next decades, ultra-high-energy neutrinos in the EeV energy range will be potentially detected by next-generation neutrino telescopes. Although their primary goals are to observe cosmogenic neutrinos and to gain insight into extreme astrophysical environments, they can also indirectly probe the nature of dark matter. In this paper, we study the projected sensitivity of up-coming neutrino radio telescopes, such as RNO-G, GRAND and IceCube-gen2 radio array, to decaying dark matter scenarios. We investigate different dark matter decaying channels and masses, from $10^7$ to $10^{15}$ GeV. By assuming the observation of cosmogenic or newborn pulsar neutrinos, we forecast conservative constraints on the lifetime of heavy dark matter particles. We find that these limits are competitive with and highly complementary to previous multi-messenger analyses.

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arXiv2023

Bump-hunting in the diffuse flux of high-energy cosmic neutrinos

The origin of the bulk of the high-energy astrophysical neutrinos seen by IceCube, with TeV--PeV energies, is unknown. If they are made in photohadronic, i.e., proton-photon, interactions in astrophysical sources, this may manifest as a bump-like feature in their diffuse flux, centered around a characteristic energy. We search for evidence of this feature, allowing for variety in its shape and size, in 7.5 years of High-Energy Starting Events (HESE) collected by the IceCube neutrino telescope, and make forecasts using larger data samples from upcoming neutrino telescopes. Present-day data reveals no evidence of bump-like features, which allows us to constrain candidate populations of photohadronic neutrino sources. Near-future forecasts show promising potential for stringent constraints or decisive discovery of bump-like features. Our results provide new insight into the origins of high-energy astrophysical neutrinos, complementing those from point-source searches.

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arXiv2023

Near-future discovery of point sources of ultra-high-energy neutrinos

Upcoming neutrino telescopes may discover ultra-high-energy (UHE) cosmic neutrinos, with energies beyond 100 PeV, in the next 10-20 years. Finding their sources would identify guaranteed sites of interaction of UHE cosmic rays, whose origin is unknown. We search for sources by looking for multiplets of UHE neutrinos arriving from similar directions. Our forecasts are state-of-the-art, geared at neutrino radio-detection in IceCube-Gen2. They account for detector energy and angular response, and for critical, but uncertain backgrounds. Sources at declination of $-45^\circ$ to $0^\circ$ will be easiest to discover. Discovering even one steady-state source in 10 years would imply that the source has an UHE neutrino luminosity at least larger than about $10^{43}$ erg/s (depending on the source redshift evolution). Discovering no transient source would disfavor transient sources brighter than $10^{53}$ erg as dominant. Our results aim to inform the design of upcoming detectors.

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arXiv2022

Point sources of ultra-high-energy neutrinos: minimalist predictions for near-future discovery

The discovery of ultra-high-energy neutrinos, with energies above 100 PeV, may soon be within reach of upcoming neutrino telescopes. We present a robust framework to compute the statistical significance of point-source discovery via the detection of neutrino multiplets. We apply it to the radio array component of IceCube-Gen2. To identify a source with $3σ$ significance, IceCube-Gen2 will need to detect a triplet, at best, and an octuplet, at worst, depending on whether the source is steady-state or transient, and on its position in the sky. The discovery, or absence, of sources significantly constrains the properties of the source population.

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arXiv2022

Axions from Neutron Star Mergers

Axion-like particles (ALP) can in principle be produced in very hot and dense astrophysical environments, escape from the extreme object where such conditions are met, and then be converted in gamma--rays in the magnetic fields intervening between the event and the Earth. This process potentially offers a new window on both the physics of the axions, and the inner working of the astrophysical objects where they are produced. Interestingly, while this process has been studied for core--collapse supernovae and other extreme astrophysical events, no estimate exists for Neutron Star Mergers, objects recently identified through the detection of gravitational waves. In this work we study the production of ALPs in neutron star mergers, finding that for a large region of the ALP parameter space its magnitude at the source is such to produce a sizable gamma-ray signal at Earth. We show detection forecasts for such events placed in nearby galaxies, finding that they are potentially observable with the Fermi--LAT, thus opening a new window into both the astrophysics of these cataclysmic events, and of new particles beyond the standard model.

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arXiv2022

Constraining axion-like particles with the diffuse gamma-ray flux measured by the Large High Altitude Air Shower Observatory

The detection of very high-energy neutrinos by IceCube experiment supports the existence of a comparable gamma-ray counterpart from the same cosmic accelerators. Under the likely assumption that the sources of these particles are of extragalactic origin, the emitted photon flux would be significantly absorbed during its propagation over cosmic distances. However, in the presence of photon mixing with ultra-light axion-like-particles (ALPs), this expectation would be strongly modified. Notably, photon-ALP conversions in the host galaxy would produce an ALP flux which propagates unimpeded in the extragalactic space. Then, the back-conversion of ALPs in the Galactic magnetic field leads to a diffuse high-energy photon flux. In this context, the recent detection of the diffuse high-energy photon flux by the Large High Altitude Air Shower Observatory (LHAASO) allows us to exclude at the $95\%$ CL an ALP-photon coupling $g_{aγ}\gtrsim 3.9-7.8 \times 10^{-11}~\mathrm{GeV^{-1}}$ for $m_{a}\lesssim 4\times10^{-7}~\mathrm{eV}$, depending on the assumptions on the magnetic fields and on the original gamma-ray spectrum. This new bound is complementary with other ALP constraints from very-high-energy gamma-ray experiments and sensitivities of future experiments.

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arXiv2022

Electron scattering of light new particles from evaporating primordial black holes

Primordial black holes are a possible component of dark matter, and a most promising way of investigating them is through the product of their Hawking evaporation. As a result of this process, any species lighter than the Hawking temperature is emitted, including possible new particles beyond the Standard Model. These can then be detected in lab-based experiments via their interaction with the Standard Model particles. In a previous work, we have first proposed and studied this scenario in the presence of an interaction between the light new species and nucleons. Here we extend this discussion to include the case of interaction with electrons. We show that the simultaneous presence of primordial black holes and species lighter than about $100$ MeV can be constrained by the measurements of direct detection experiments, such as XENON1T, and water Cherenkov neutrino detectors, such as Super-Kamiokande. Our results provide a complementary and alternative way of investigation with respect to cosmological and collider searches.

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arXiv2022

The TopFlavor scheme in the context of $W'$ searches at LHC

Many extensions of the Standard Model predict the existence of new charged or neutral gauge bosons, with a wide variety of phenomenological implications depending on the model adopted. The search for such particles is extensively carried through at the Large Hadron Collider (LHC), and it is therefore of crucial importance to have for each proposed scenario quantitative predictions that can be matched to experiments. In this work we focus on the implications of one of these models, the TopFlavor Model, proposing a charged $\text{W}^\prime$ boson that has preferential couplings to the third generation fermions. We compare such predictions to the ones from the so called Sequential Standard Model (SSM), that is used as benchmark, being one of the simplest and most commonly considered models for searches at the LHC. We identify the parameter space still open for searches at the LHC, and in particular we show that the cross section for the processes $pp \to \text{W}^\prime \to τν$ and $pp \to \text{W}^\prime \to tb$ can be up to two orders of magnitude smaller with respect to the SSM, depending on the free parameters of the model, like the particle mass and its width. This study makes the case for further searches at the LHC, and shows how a complete and systematic model independent analysis of $\text{W}^\prime$ boson phenomenology at colliders is essential to provide guidance for future searches.

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arXiv2022

Neutrino Self-Interactions: A White Paper

Neutrinos are the Standard Model (SM) particles which we understand the least, often due to how weakly they interact with the other SM particles. Beyond this, very little is known about interactions among the neutrinos, i.e., their self-interactions. The SM predicts neutrino self-interactions at a level beyond any current experimental capabilities, leaving open the possibility for beyond-the-SM interactions across many energy scales. In this white paper, we review the current knowledge of neutrino self-interactions from a vast array of probes, from cosmology, to astrophysics, to the laboratory. We also discuss theoretical motivations for such self-interactions, including neutrino masses and possible connections to dark matter. Looking forward, we discuss the capabilities of searches in the next generation and beyond, highlighting the possibility of future discovery of this beyond-the-SM physics.

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