arXiv subjects

Diego Redigolo

Publications and source records attributed to Diego Redigolo.

At least 19 recordsLinked to original sources

arXiv2026

The soft volume of ultra-high energy neutrinos experiments

We develop a semi-analytical framework to map ultra-high-energy neutrino fluxes onto event rates at neutrino telescopes. The formulation is based on the Boltzmann equation for the distribution of secondary muons produced by neutrino interactions in matter, and naturally accounts for the effective target volume relevant for through-going tracks. This "soft volume" is controlled by muon propagation and stochastic energy losses, and can be significantly larger than the instrumented detector volume. Exploiting the dominance of soft energy losses, we derive a controlled second-order expansion of the collision operator, reducing the transport problem to a drift-diffusion equation in energy space, with rare hard scatterings treated perturbatively. The resulting master formula provides a fast alternative to full Monte Carlo simulations while retaining a direct connection to the microscopic muon energy-loss processes. We apply the formalism to IceCube through-going muon data, marginalizing over theoretical uncertainties in the transport coefficients, and obtain a diffuse-flux fit compatible with the experimental result. We also revisit the interpretation of the ultra-high-energy track event reported by KM3NeT, assessing its consistency with IceCube non-observation in the same energy range. Our results provide a first-principles bridge between neutrino-flux models and track-event observables, with direct applications to precision neutrino astronomy and searches for physics beyond the Standard Model.

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arXiv2026

Post-Recombination Fluctuations from a Sequestered Dark Sector

We develop a formalism to characterize the imprints of late-time sources of cosmological fluctuations under the sole assumption that the injection occurs on timescales short compared to the horizon. For post-recombination injections, we derive the general modification of photon geodesics in the presence of scalar, vector, and tensor perturbations, and compute the resulting impact on the Cosmic Microwave Background through the integrated Sachs-Wolfe effect. We show that the signal is generically dominated by instantaneous injections of anisotropic stress. As an application, we consider first-order phase transitions in a sequestered dark sector and show that current observations constrain fractional energy injections at the permille level.

astro-ph.CO↗

arXiv2026

Probing Neutrino Compositeness with Invisible and Displaced Signals

We explore the possibility that neutrinos couple to an interacting sterile sector, providing a novel portal that generalizes the heavy neutral lepton portal to a composite setting. For a low confinement scale, high-energy neutrino beams can disintegrate into collimated sprays of hidden states, referred to as dark jets. This dynamics gives rise to two characteristic signatures in high energy neutrino beams. First, long-lived dark resonances can enhance the neutral-current to charged-current ratio. Second, shorter-lived dark states produced in neutrino neutral currents can produce single or multiple displaced vertices and even emerging jets, depending on the kinematics. These signals probe regions of parameter space beyond existing constraints from meson, electroweak, and Higgs decays, as well as from searches for displaced decays at beam dump experiments. We study these phenomena within broad classes of ultraviolet completions and identify scenarios in which high-energy neutrino beams provide leading sensitivity to neutrino compositeness. Such scenarios generically induce higher-dimensional contact interactions, which we classify and study alongside their complementary experimental signatures. Finally, we outline an experimental program spanning both the intensity and energy frontiers. Near-term neutrino facilities (DUNE, FPF) and running flavor experiments (LHCb, Belle II) can probe neutrino compositeness through neutrino disintegration into dark jets and displaced B-meson decays. Future colliders, particularly the Future Circular Collider (FCC-ee), will ultimately provide the strongest sensitivity to the compositeness scale via displaced Z decays.

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arXiv2025

Testing Real WIMPs with CTAO

We forecast the reach of the upcoming Cherenkov Telescope Array Observatory (CTAO) to the full set of real representations within the paradigm of minimal dark matter. We employ effective field theory techniques to compute the annihilation cross section and photon spectrum that results when fermionic dark matter is the neutral component of an arbitrary odd and real representation of SU(2), including the Sommerfeld enhancement, next-to-leading log resummation of the relevant electroweak effects, and the contribution from bound states. We also compute the corresponding signals for scalar dark matter, with the exception of the bound state contribution. Results are presented for all real representations from the $\sim$3 TeV triplet (or wino), a $\mathbf{3}$ of SU(2), to the $\sim$300 TeV tredecuplet, a $\mathbf{13}$ of SU(2) that is at the threshold of the unitarity bound. Using these results, we forecast that with 500 hrs of Galactic Center observations and assuming background systematics are controlled at the level of ${\cal O}(1\%)$, then should no signal emerge, CTAO could exclude all representations up to the $\mathbf{11}$ of SU(2) in even the most conservative models for the dark-matter density in the inner galaxy, in both the fermionic and scalar dark matter cases. Assuming the default CTAO configuration, the tredecuplet will marginally escape exclusion, although we outline steps that CTAO could take to test even this scenario. In summary, CTAO appears poised to make a definitive statement on whether real WIMPs constitute the dark matter of our universe.

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arXiv2025

Invisible jets from composite neutrinos

We propose a novel experimental probe of neutrino couplings to a composite sterile sector, leveraging the unique signature of neutrino disintegration into "invisible jets" in high-energy neutrino scattering. Focusing on scenarios where the invisible jet invariant mass significantly exceeds the confinement scale, we compute production rates within the conformal window. In this regime, invisible jet production leads to an energy-dependent enhancement of the neutral-to-charged current ratio in neutrino-nucleus scattering. Using NuTeV measurements, we derive new bounds and assess the sensitivity of upcoming experiments such as SHiP and the Forward Physics Facility at CERN. We sketch models where these probes surpass constraints from electroweak gauge boson and Higgs invisible branching ratios. In contrast, neutrino-electron scattering modifications are suppressed by the lower center-of-mass energy and are unlikely to be observable at DUNE.

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arXiv2025

Exploring ultra-high energy neutrino experiments through the lens of the transport equation

We develop a first-principles formalism, based on the transport equation in the line-of-sight approximation, to link the expected number of muons at neutrino telescopes to the flux of neutrinos at the Earth's surface. We compute the distribution of muons inside Earth, arising from the up-scattering of neutrinos close to the detector, as well as from the decay of taus produced farther away. This framework allows one to account for systematic uncertainties, as well as to clarify the assumptions behind definitions commonly used in the literature, such as the effective area. We apply this formalism to analyze the high-energy muon event recorded by KM3NeT, with a reconstructed energy of $ 120^{+110}_{-60} \, \mathrm{PeV}$ and an elevation angle of $\left(0.54\pm 2.4\right)^\circ$, in comparison with the non-observation of similar events by IceCube. We find a $3.1\,\sigma$ tension between the two experiments, assuming a diffuse neutrino source with a power-law energy dependence. Combining both datasets leads to a preference for a very low number of expected events at KM3NeT, in stark contrast to the observed data. The tension increases both in the case of a diffuse source peaking at the KM3NeT energy and of a steady point source, whereas a transient source may reduce the tension down to $1.6\,\sigma$. The formalism allows one to treat potential beyond-the-Standard-Model sources of muons, and we speculate on this possibility to explain the tension.

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arXiv2025

Closing in on Pop-III Stars: Constraints and Predictions Across the Spectrum

The absence of direct high redshift observations poses a significant challenge in understanding the properties of first stars. Nonetheless, the cumulative effect of entire stellar populations can be studied with current data. In this work we use a combination of high redshift observables in order to infer the formation and emission properties of the first stellar populations: high redshift UVLFs, the optical depth of CMB photons to reionization, hydrogen absorption lines in quasar spectra, and measurements of the soft cosmic X-ray background. We study two minimal models of stellar population: i) a single, Pop-II, stellar population which dominates throughout Cosmic Dawn, ii) two distinct stellar populations, Pop-II and Pop-III, dominating at different times with the transition between them taken as a free parameter. We set strong constraints on the properties of Pop-II stars, and upper limits on the formation and multi-wavelength emission of Pop-III stars. After applying the constraints above, we present the viable envelopes of the 21-cm global signal with and without Pop-III stars. We identify a region in the parameter space of the two population model which predicts a global 21-cm signal distinctive from that of the single population one. A measurement of such a signal would be a strong indication for the presence of Pop-III stars at early times.

astro-ph.CO↗

arXiv2024

Displaced Searches for Axion-Like Particles and Heavy Neutral Leptons at Mu3e

We present strategies for the Mu3e experiment to search for light, weakly coupled particles produced in rare muon decays, focusing on displaced $e^+e^-$ decays within the hollow target. In most scenarios the backgrounds can be fully suppressed with a suitable set of cuts. We furthermore quantify the interplay between displaced and prompt searches at Mu3e and existing constraints, showing how Mu3e has a unique opportunity to probe unexplored parameter space.

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arXiv2024

Looking for WIMPs through the neutrino fogs

We revisit the expected sensitivity of large-scale xenon detectors to Weakly Interacting Massive Particles (WIMPs). Assuming current primary noise sources can be mitigated, we find that with the present discrimination power between nuclear and electron recoils, the experimental sensitivity is limited not only by atmospheric neutrinos' nuclear recoils (''nuclear recoil neutrino fog'') but also by solar neutrinos' electron-recoil events (''electron recoil neutrino fog''). While this is known by experimentalists, it is often missed or misunderstood by theorists, and we therefore emphasize this effect. We set up a realistic detector simulation to quantify the contamination of the WIMP signal from both these neutrino backgrounds. We observe that the electron-recoil background remains significant even for signal rates exceeding those of atmospheric neutrinos, as predicted by most electroweak WIMP candidates. We update the projections for the required exposure to exclude/discover a given electroweak WIMP, streamlining the computation of their signal rates and uncertainties. We show that all of the real WIMPs with zero hypercharge can be excluded (discovered) with a 50 tonne year (300 tonne year) exposure. A similar exposure will allow to probe a large portion of the viable parameter space for complex WIMP with non-zero hypercharge.

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arXiv2024

Large CP violation in flavor violating muon decays

We identify new room for CP violation in lepton flavor violating observables not bound by the electric dipole moment of leptons. By focusing on new physics in the muon-electron sector, we show that CP violation can make its first appearance in lepton flavor violating muon decays rather than in the electric dipole moment of the electron, further motivating the experimental program of Mu3e. We tackle this issue by performing the full one-loop running and matching from the low energy observables at the muon scale, including the T-odd asymmetry in $μ\to3e$ decays, to the Standard Model effective field theory above the electroweak scale. We then sketch a simple UV model that can give rise to these patterns.

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arXiv2024

Unveiling dark forces with measurements of the Large Scale Structure of the Universe

Cosmology offers opportunities to test Dark Matter independently of its interactions with the Standard Model. We study the imprints of long-range forces acting solely in the dark sector on the distribution of galaxies, the so-called Large Scale Structure (LSS). We derive the strongest constraint on such forces from a combination of Planck and BOSS data. Along the way we consistently develop, for the first time, the Effective Field Theory of LSS in the presence of new dynamics in the dark sector. We forecast that future surveys will improve the current bound by an order of magnitude.

astro-ph.CO↗

arXiv2024

From 100 kpc to 10 Gpc: Dark Matter self-interactions before and after DESI

We consider Dark Matter self-interactions mediated by ultralight scalars. We show that effectively massless mediators lead to an enhancement of the matter power spectrum, while heavier mediators lead to a suppression, together with a feature around their Jeans scale. We derive the strongest present constraints by combining Planck and BOSS data. The recent DESI measurements of Baryon Acoustic Oscillations exhibit a mild $2\sigma$ preference for long-range self-interactions, as strong as $4$ per mille of the gravitational coupling. Full-shape analyses of forthcoming DESI and Euclid data will confirm or disprove such a hint.

astro-ph.CO↗

arXiv2024

Fusing photons into diphoton resonances at Belle II and beyond

We propose a new search for a diphoton resonance in the $e^+e^-+γγ$ final state at Belle II that improves the expected reach compared to the $γ+γγ$ channel in most of the available mass range. For simplicity we show our results in the simple parameter space of an ALP coupled solely to Standard Model photons. In addition, we show how an extension of the forward coverage of Belle II, or another similar experiment at the high intensity frontier, could improve the reach in our channel. We show that such a forward extension can be advantageous even with a loss of a factor 100 in luminosity compared to Belle II.

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arXiv2024

The Supercooling Window at Weak and Strong Coupling

Supercooled first order phase transitions are typical of theories where conformal symmetry is predominantly spontaneously broken. In these theories the fate of the flat scalar direction is highly sensitive to the size and the scaling dimension of the explicit breaking deformations. For a given deformation, the coupling must lie in a particular region to realize a supercooled first order phase transition. We identify the supercooling window in weakly coupled theories and derive a fully analytical understanding of its boundaries. Mapping these boundaries allows us to identify the deformations enlarging the supercooling window and to characterize their dynamics analytically. For completeness we also discuss strongly coupled conformal field theories with an holographic dual, where the complete characterization of the supercooling window is challenged by calculability issues.

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arXiv2024

Probing New Physics at Cosmic Dawn with 21-cm Cosmology

21-cm cosmology provides an exciting opportunity to probe new physics dynamics in the early universe. In particular, a tiny sub-component of dark matter that interacts strongly with the visible sector may cool the gas in the intergalactic medium and significantly alter the expected absorption signal at Cosmic Dawn. However, the information about new physics in this observable is obscured by astrophysical systematic uncertainties. In the absence of a microscopic framework describing the astrophysical sources, these uncertainties can be encoded in a bottom up effective theory for the 21-cm observables in terms of unconstrained astrophysical fluxes. In this paper, we take a first step towards a careful assessment of the degeneracies between new physics effects and the uncertainties in these fluxes. We show that the latter can be constrained by combining measurements of the UV luminosity function, the Planck measurement of the CMB optical depth to reionization, and an upper bound on the unresolved X-ray flux. Leveraging those constraints, we demonstrate how new physics signatures can be disentangled from astrophysical effects. Focusing on the case of millicharged dark matter, we find sharp predictions, with small uncertainties within the viable parameter space.

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arXiv2023

Angling for Insights: Illuminating Light New Physics at Mu3e through Angular Correlations

We examine the capability of Mu3e to probe light new physics scenarios that produce a prompt electron-positron resonance and demonstrate how angular observables are instrumental in enhancing the experimental sensitivity. We systematically investigate the effect of Mu3e's expected sensitivity on the parameter space of the dark photon, as well as on axion-like particles and light scalars with couplings to muons and electrons.

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arXiv2023

A Robust Search for Lepton Flavour Violating Axions at Mu3e

We propose a search at Mu3e for lepton flavor violating axion(-like) particles in $μ\to 3e + a$ decays. By requiring an additional $e^+e^-$ pair from internal conversion, one can circumvent the calibration challenges which plague the $μ\to e+a$ channel for axions lighter than 20 MeV. Crucially, the corresponding reduction in signal rate is to a large extent compensated for by Mu3e's ability to resolve highly collimated tracks. For phase I of Mu3e, we project a sensitivity to decay constants as high as $6\times 10^9$ GeV which probes uncharted parameter space in scenarios of axion dark matter. The sensitivity to axions which couple primarily to right-handed leptons can be further improved by leveraging the polarisation of the muon beam.

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arXiv2023

Fusing photons into nothing, a new search for invisible ALPs and Dark Matter at Belle II

We consider an axion-like particle coupled to the Standard Model photons and decaying invisibly at Belle II. We propose a new search in the $e^+e^-+\text{invisible}$ channel that we compare against the standard $γ+\text{invisible}$ channel. We find that the $e^+e^-+\text{invisible}$ channel has the potential to ameliorate the reach for the whole ALP mass range. This search leverages dedicated kinematic variables which significantly suppress the Standard Model background. We explore the implications of our expected reach for Dark Matter freeze-out through ALP-mediated annihilations.

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