arXiv subjects

Edoardo Vitagliano

Publications and source records attributed to Edoardo Vitagliano.

At least 19 recordsLinked to original sources

arXiv2026

Production of Leptophilic Bosons in Ultradegenerate Relativistic Matter

Neutron stars (NSs) are powerful factories for new particles with masses up to the 100~keV range. These compact stars contain significant amounts of protons, electrons, and muons. We deduce the emission rates for new scalar, vector, and pseudoscalar bosons coupling to electrons and muons. For muonic vector bosons, in addition to direct emission from leptons in incoherent scatterings with the medium, a competing channel is the coherent excitation of the lepton population electromagnetically induced by incoherent hadronic scatterings - an effective in-medium coupling. For muonic scalar bosons, emission from the effective in-medium coupling to electrons is always dominant due to their relativistically boosted emission. Pseudoscalars can only be emitted through incoherent leptonic scatterings. If protons are superconducting, the scalar and vector energy loss rates scale as $T^4$, the pseudoscalar ones as $T^6$, to be compared with $T^8$ for neutrino losses by the modified Urca (MUrca) process. For normal-conducting protons, the damping of transverse photons implies instead scalings with a power $T^{11/3}$ for scalars, and $T^{17/3}$ for pseudoscalars; vectors, emitted by nonrelativistic protons in the nonsuperconducting regime, still scale as $T^4$. Our results can be used to constrain the leptophilic coupling strengths through observed NS cooling ages.

hep-ph↗

arXiv2026

Neutron Star Bounds on Muonic Fifth Forces from Picometer to Meter Scales

Testing muonic fifth forces is difficult because muons are scarce in ordinary matter. However, they are abundant in neutron stars. We show that this population responds coherently to electromagnetic fluctuations induced by proton and electron collisions, emitting the fifth-force mediator and cooling the star. This energy loss constrains $g_{Xμ}\lesssim 10^{-13}$ for scalars with $m_ϕ\lesssim 100$ keV and vectors with $10^{-5}\,\mathrm{eV}\lesssim m_V\lesssim 100$ keV, far more strongly than SN 1987A cooling. Vector forces at smaller $m_V$ deplete muons, suppressing the coherent response. Cooling from incoherent muon scattering still constrains $g_{V μ}\lesssim 2.5\times 10^{-12}$ for $1.3\times 10^{-7}\,\mathrm{eV}\lesssim m_V\lesssim 10^{-5}$ eV. Together, these bounds provide the most sensitive probes of muonic interactions across a broad range of parameters.

hep-ph↗

arXiv2026

Magnetic Turbulence Boosts Supernova Signals of Axion-Photon Conversion

Magnetic fields between a supernova (SN) and Earth convert axions into gamma rays. The absence of such a signal in coincidence with SN 1987A neutrinos, using the coherent Milky Way field, provides well-studied constraints on $g_{ap}\times g_{aγ}$ (axion-proton times axion-photon couplings) and on $g_{aγ}$ alone. We show that the small-scale power of the turbulent magnetic field component boosts axion-photon conversion and, crucially, extends sensitivity to larger masses. The turbulent field components of the Milky Way and of the Large Magellanic Cloud (hosting SN 1987A) yield improvements of up to two orders of magnitude in $g_{ap}\times g_{aγ}$. Turbulence should likely impact the sensitivity of other searches based on other axion-photon conversion sites, such as starburst galaxies.

hep-ph↗

arXiv2026

Small Progenitors, Large Couplings: Type Ic Supernova Constraints on Radiatively Decaying Particles

Supernova (SN) 1987A provides classic bounds on gamma-ray flashes from the radiative decay of sub-GeV particles, but the latter may decay so rapidly as to be shielded by the stellar envelope. Using axionlike particles with photon coupling as a benchmark, we show that Type Ic core-collapse supernovae largely evade this attenuation due to their compact progenitors. We identify two regimes. At small couplings, while individual flashes may be missed by Fermi-LAT, the high Type Ic rate enables a stacking analysis of nondetections. At larger couplings, decay photons trigger fireball formation; the absence of a signal from the rare broad-lined Type Ic SN 1998bw excludes this scenario. The resulting bounds significantly exceed those from SN 1987A for short decay lengths.

hep-ph↗

arXiv2026

Axions at the meV Crossroads: Theory, Cosmology, Astrophysics, and Experiments

The meV mass range has emerged as a focal point in axion physics, where advances in theory, cosmology, astrophysics, and experimental techniques converge. Axions in this mass range are theoretically well motivated, can arise in ultraviolet-complete models, and can have significant cosmological impacts as dark matter or dark radiation. In parallel, their efficient production in stellar and supernova environments provides powerful astrophysical probes. Here, we provide a comprehensive overview of meV axions across these domains, highlighting both established results and open questions. We discuss the theoretical underpinnings of meV axions, their cosmological and astrophysical signatures, and the diverse experimental strategies -- ranging from helioscopes and haloscopes to quasiparticle systems and large-volume Cherenkov detectors -- that aim to explore this regime. The convergence of these approaches emphasizes the pivotal role of the meV mass range for axion discovery in the coming years, identifying meV axions as a key probe for testing beyond-Standard-Model physics. This review document is the direct outcome of the discussions at the dedicated workshop "The meV Mass Axion Frontier: Challenges and Opportunities", held at Laboratori Nazionali di Frascati (IT) on 27--28 October 2025, and organized by the EU funded COST Action "Cosmic WISPers in the Dark Universe: Theory, astrophysics, and experiments" (CA21106, https://www.cost.eu/actions/CA21106). Its aim is to provide an overview of current efforts in meV axion research, their motivations, and the research goals that animate the community involved in this search.

hep-ph↗

arXiv2026

Minimal Proton-Mass Dark Matter

We present a minimal dark matter scenario: a single complex scalar carrying baryon and lepton number, with no new exact stabilizing symmetry. Its leading interaction is a dimension-7 semileptonic portal that, below confinement, generates a low-energy Yukawa coupling with the proton and electron. Requiring absolute stability of both the proton and dark matter forces the dark matter mass into a narrow window around the proton mass, which may be anthropically selected. Despite its minimal field content, the model can be probed by many observables: proton burning in stars, hydrogen decay, brown dwarfs and neutron star heating, and nucleon decay-like signatures in direct detection. UV-dominated freeze-in produces the observed relic abundance. This framework provides a unique testable example of dark matter arising from a minimal extension of the Standard Model.

hep-ph↗

arXiv2026

Millicharged Particle Constraints from Asymptotic Giant Branch Stars

We investigate the effect of millicharged particles (MCPs) with electric charge $qe\ll e$ and mass $m_χ$ on the late-stage evolution phases of low-mass stars in globular clusters. We predict the $R_2$ parameter -- the ratio of the number of stars in the asymptotic giant branch (AGB) phase to the number of stars in the horizontal branch (HB) phase -- and compare it against globular cluster data. While the production of MCPs shortens both the HB and AGB lifetimes, a larger reduction in the AGB phase arises from the higher temperatures in the helium-burning shell. We find the strongest bounds in the range $10\,\mathrm{keV}\lesssim m_χ\lesssim 100\,\mathrm{keV}$, reaching charges as small as $q\simeq 5\times10^{-13}$ and surpassing existing constraints by up to two orders of magnitude.

hep-ph↗

arXiv2026

Stripped-Envelope Supernovae for QCD Axion Detection

QCD axions would be copiously produced in the proto-neutron star formed in a core-collapse supernova (SN). After escaping, they would convert into gamma rays in the Galactic magnetic field and, as recently shown, in that of the progenitor star itself. Here, we show that Type Ibc SNe -- whose progenitors have lost their hydrogen or even helium envelopes -- are the optimal targets for this search. The stripped progenitors are much more compact, and they show larger magnetic fields than both red and blue supergiants, the progenitors of Type IIP/L SNe. If the next galactic SN is of Type Ibc, Fermi-LAT or a similar gamma-ray satellite might be able to discover the QCD axion down to masses as small as $m_a\simeq 10^{-4}\,\rm eV$ (Peccei-Quinn scale $f_a\simeq 10^{11} \,\rm GeV$).

hep-ph↗

arXiv2026

Supernova production of axion-like particles coupling to electrons, reloaded

We revisit the production of axion-like particles (ALPs) coupled to electrons at tree-level in a relativistic plasma. We explicitly demonstrate the equivalence between pseudoscalar and derivative couplings, incorporate previously neglected processes for the first time-namely, semi-Compton production ($γe^-\rightarrow a e^-$) and pair annihilation ($e^+e^-\rightarrow aγ$)-and derive analytical expressions for the bremsstrahlung ($e^- N\to e^- N a$) production rate, enabling a more computationally efficient evaluation of the ALP flux. Additionally, we assess uncertainties in the production rate arising from electron thermal mass corrections, electron-electron Coulomb interactions, and the Landau-Pomeranchuk-Migdal effect. The ALP emissivity is made available in a public repository as a function of the ALP mass, the temperature, and the electron chemical potential of the plasma. Finally, we examine the impact of ALP production and subsequent decays on astrophysical observables, deriving the leading bounds on ALPs coupling to electrons. At small couplings, the dominant constraints come from the previously neglected decay $a\to e^+ e^-γ$, except for a region of fireball formation where SN 1987A X-ray observations offer the best probe. At large couplings, bounds are dominated by the energy deposition argument, with a recently developed new prescription for the trapping regime.

hep-ph↗

arXiv2026

Muonic Boson Limits: Supernova Redux

We derive supernova (SN) bounds on muon-philic bosons, taking advantage of the recent emergence of muonic SN models. Our main innovations are to consider scalars $ϕ$ in addition to pseudoscalars $a$ and to include systematically the generic two-photon coupling $G_{γγ}$ implied by a muon triangle loop. This interaction allows for Primakoff scattering and radiative boson decays. The globular-cluster bound $G_{γγ}<0.67\times10^{-10}~{\rm GeV}^{-1}$ derived for axion-like particles carries over to the muonic Yukawa couplings as $g_a<3.1\times10^{-9}$ and $g_ϕ< 4.6\times10^{-9}$ for $m_{a,ϕ}\lesssim 100$ keV, so SN arguments become interesting mainly for larger masses. If bosons escape freely from the SN core the main constraints originate from SN1987A $γ$ rays and the diffuse cosmic $γ$-ray background. The latter allows at most $10^{-4}$ of a typical total SN energy of $E_{\rm SN}\simeq3\times10^{53}$erg to show up as $γ$ rays, for $m_{a,ϕ}\gtrsim 100$keV implying $g_a \lesssim 0.9\times10^{-10}$ and $g_ϕ\lesssim 0.4\times10^{-10}$. In the trapping regime the bosons emerge as quasi-thermal radiation from a region near the neutrino sphere and match $L_ν$ for $g_{a,ϕ}\simeq 10^{-4}$. However, the $2γ$ decay is so fast that all the energy is dumped into the surrounding progenitor-star matter, whereas at most $10^{-2}E_{\rm SN}$ may show up in the explosion. To suppress boson emission below this level we need yet larger couplings, $g_{a}\gtrsim 2\times10^{-3}$ and $g_ϕ\gtrsim 4\times10^{-3}$. Muonic scalars can explain the muon magnetic-moment anomaly for $g_ϕ\simeq 0.4\times10^{-3}$, a value hard to reconcile with SN physics despite the uncertainty of the explosion-energy bound. For generic axion-like particles, this argument covers the "cosmological triangle" in the $G_{aγγ}$--$m_a$ parameter space.

hep-ph↗

arXiv2026

The Black Hole Mass Gap as a New Probe of Millicharged Particles

We investigate the impact of millicharged particles (MCPs) on massive stars undergoing pulsational pair-instability supernovae and on the location of the lower edge of the black hole mass gap. We find that energy losses due to MCP emission weaken the pulsations, allowing the star to retain more mass and thereby shifting the lower edge of the mass gap to higher black hole masses. The mass gap is sensitive to a region of MCP parameter space with masses $35\,{\rm keV}\lesssim m_χ\lesssim 200\,{\rm keV}$ and charges $10^{-10}\lesssim q \lesssim 10^{-9}$, which remains unconstrained by existing astrophysical probes. If confirmed, recent gravitational wave observations placing the lower edge of the mass gap near $45\,{\rm M}_\odot$ would translate directly into bounds on this parameter space.

hep-ph↗

arXiv2026

Millicharged Particle Production During Late-Stage Stellar Evolution

Stars are natural sources of feebly interacting particles, including putative particles with mass $m_χ$ and electric charge $qe$. The emission of such millicharged particles (MCPs) causes an energy loss which can alter stellar evolution. While MCP production rates have been computed for different plasma parameters, they have yet to be derived for the conditions relevant to late stages of stellar evolution, in which the temperature can reach values $T\simeq 10-100\,\rm keV$ while the plasma frequency is $ω_{\rm pl}\ll T$. In this paper, we compute the MCP energy-loss rates relevant for pre-supernova objects, finding three different regimes in which the dominant processes are respectively plasmon decay ($m_χ< ω_{\rm pl}/2$), Compton-like scattering ($m_χ> ω_{\rm pl}/2$, $T\lesssim 0.5\,\rm MeV$), and electron-positron annihilation. We obtain semi-analytical fits for the energy-loss rates suitable for implementation in stellar evolution codes.

hep-ph↗

arXiv2026

Axion-photon conversion in transient compact stars: Systematics, constraints, and opportunities

We study magnetic conversion of ultra-relativistic axion-like particles (ALPs) into photons in compact-star environments, focusing on the hot, transient conditions of core-collapse supernova (SN) remnants and neutron-star mergers (NSMs). We address previously overlooked uncertainties, particularly the suppression caused by ejected matter near the stellar surface, a region crucial to the conversion process. We derive analytical expressions for the transition rate; they reveal the influence of key parameters and their uncertainties. We update constraints using historical gamma-ray data from SN~1987A and find $g_{aγ}<5\times10^{-12}~{\rm GeV}^{-1}$ for $m_a\lesssim10^{-9}$ eV. We also forecast sensitivities for a future Galactic SN and for NSMs, assuming observations with Fermi-LAT or similar gamma-ray instruments. We distinguish ALPs -- defined as coupling only to photons and produced via Primakoff scattering -- from axions, which also couple to nucleons and emerge through nuclear bremsstrahlung. We omit pionic axion production due to its large uncertainties and inconsistencies, though it could contribute comparably to bremsstrahlung under optimistic assumptions. For the compact sources, we adopt time-averaged one-zone models, guided by numerical simulations, to enable clear and reproducible parametric studies.

hep-ph↗

arXiv2025

Energy transfer by feebly interacting particles in supernovae: the trapping regime

Feebly interacting particles, such as sterile neutrinos, dark photons, and axions, can be abundantly produced in the proto-neutron star (PNS) formed in core-collapse supernovae (CCSNe). These particles can decay into photons or charged leptons, depositing energy outside the PNS. Strong bounds on new particles can thus be derived from the observed luminosity of CCSNe, with even tighter bounds obtained from low-energy SNe observations. For the first time we highlight that, at sufficiently large couplings, particle production \textit{outside} the PNS must also be considered. Using the prototypical case of axions coupling to two photons, we show that at large couplings the energy transfer from PNS to its surroundings is diffusive rather than ballistic, substantially reducing the deposited energy. Our findings have implications for the parameter space of particles probed in beam dump experiments and for dark matter models involving a sub-GeV mediator.

hep-ph↗

arXiv2025

Leading bounds on micro- to picometer fifth forces from neutron star cooling

The equivalence principle and the inverse-square law of gravity could be violated at short distances ($10^{-6}$ to $10^{-12}$ meters) by scalars sporting a coupling $g_N$ to nucleons and mass $\mathrm{eV}\lesssim m_ϕ\lesssim\rm MeV$. We show for the first time that stringent bounds on the existence of these scalars can be derived from the observed cooling of nearby isolated neutron stars (NSs). Although NSs can only be used to set limits comparable to the classic SN 1987A cooling bound in the case of pseudoscalars such as the QCD axion, the shallow temperature dependence of the scalar emissivity results in a huge enhancement in the effect of $ϕ$ on the cooling of cold NSs. As we do not find evidence of exotic energy losses, we can exclude couplings down to $g_N\lesssim 5 \times 10^{-14}$. Our new bound supersedes all existing limits on scalars across six orders of magnitude in $m_ϕ$. These conclusions also extend to Higgs-portal models, for which the bound on the scalar-Higgs mixing angle is $\sinθ\lesssim 6\times 10^{-11}$.

hep-ph↗

arXiv2025

NuSTAR bounds on radiatively decaying particles from M82

Axions and other putative feebly interacting particles (FIPs) with a mass of tens to several hundreds of keVs can be produced in stellar cores with a Lorentz boost factor $E_a/m_a\lesssim 10$. Thus, starburst galaxies such as M82 are efficient factories of slow axions. Their decay $a\rightarrowγγ$ would produce a large flux of X-ray photons, peaking around $100$ keV and spread around the galaxy by an angle that can be relatively large. We use observations of the Nuclear Spectroscopic Telescope Array (NuSTAR) mission to show that the absence of these features can constrain $30-500$ keV axion masses into uncharted regions for axion-photon coupling of $g_{aγ}\sim 10^{-10}-10^{-12}\,\rm GeV^{-1}$. Our argument can be applied to other heavy FIPs and astrophysical sources that are hot enough to produce them, yet cold enough to avoid large boost factors which slow down the decay.

hep-ph↗

arXiv2025

Exploring the Dark Universe: A European Strategy for Axions and other WISPs Discovery

Axions and other very weakly interacting slim (with $m <$ 1 GeV) particles (WISPs) are a common feature of several extensions of the Standard Model of Particle Physics. The search of WISPs was already recommended in the last update of the European strategy on particle physics (ESPP). After that, the physics case for WISPs has gained additional momentum. Indeed, WISPs may provide a new paradigm to explain the nature of dark matter and puzzling astrophysical and particle physics observations. This document briefly summarizes current searches for WISPs and the perspectives in this research field for the next decade, ranging from their theoretical underpinning, over their indirect observational consequences in astrophysics, to their search in laboratory experiments. It is stressed that in Europe a rich, diverse, and low-cost experimental program is already underway with the potential for one or more game-changing discoveries. In this context, it is also reported the role of the EU funded COST Action ''Cosmic WISPers in the Dark Universe: Theory, astrophysics, and experiments'' (CA21106, https://www.cost.eu/actions/CA21106) in coordinating and supporting WISPs searches in Europe, shaping a roadmap to track the strategy to guarantee a European leadership in this field of research. This document has been submitted in March 2025 as an input to the update process of the ESPP.

hep-ph↗

arXiv2025

Domain wall interpretation of the PTA signal confronting black hole overproduction

Recently, Pulsar Timing Array (PTA) collaborations have detected a stochastic gravitational wave background (SGWB) at nano-Hz frequencies, with Domain Wall networks (DWs) proposed as potential sources. To be cosmologically viable, they must annihilate before dominating the universe energy budget, thus generating a SGWB. While sub-horizon DWs shrink and decay rapidly, causality requires DWs with super-horizon size to continue growing until they reach the Hubble horizon. Those entering the latest can be heavier than a Hubble patch and collapse into Primordial Black Holes (PBHs). We conduct a Bayesian analysis of the PTA signal, interpreting it as an outcome of SGWB from DW networks, with a prior ensuring no PBH overproduction. Our findings indicate that DWs result in the production of solar-mass PBHs. The binary mergers occurring within these PBHs generate a second SGWB in the kilo-Hz domain which could be observable in on-going or planned Earth-based interferometers.

gr-qc↗