A dense neutrino gas can exhibit collective flavor oscillations, driven by neutrino–neutrino forward scattering, which profoundly affect flavor evolution in core-collapse supernovae and the early Universe. While numerous studies have shown that a zero crossing in the difference of flavor distributions ($g_{\Gamma}$) of neutrinos determines the existence and character of instabilities, a...
Among the few methods to probe the early Universe through the observation of primordial particles, one possibility remains relatively unexplored: the detection of high-energy neutrinos emitted shortly after the Big Bang, originating from the decay or annihilation of early-Universe relics.
We present a general study of this scenario. First, we emphasise that such neutrinos could exhibit...
The KM3NeT collaboration recently reported the observation of KM3-230213A, a neutrino event with an energy of 220 PeV, $\mathcal{O}(10)$ times more energetic than the highest-energy neutrino in IceCube’s catalog. Despite its larger effective area and longer data-taking period, IceCube has not observed similar events, leading to a tension quantified between ~2$\sigma$ and 3.5$\sigma$, depending...
In the presence of a finite modular flavour symmetry, fermion mass hierarchies may be generated by a slight deviation of the modulus from a symmetric point. This small parameter governing charged-lepton mass hierarchies may also be responsible for the breaking of lepton number in a symmetry-protected low-scale seesaw. In this talk, I will illustrate the implementation and the phenomenological...
Decays of relic particles into neutrinos can leave a strong imprint on the light elements formed during Big Bang Nucleosynthesis (BBN) if the decay happens before recombination. In this talk, I will discuss the effect of injecting neutrinos at lifetimes larger than 10⁴ s, focusing on the disintegration of the light elements. Several key processes are at play, including final-state radiation...
The matter-antimatter asymmetry of the Universe represents one of the main open questions in particle physics and cosmology. In this talk, we will present a novel realization of cold baryogenesis, a mechanism involving the formation and decay of Standard Model SU(2)-textures, that relies on the out-of-equilibrium dynamics during a strong first order electroweak phase transition. By performing...
We introduce a new mechanism where we claim that the Charge-Parity (CP) violation from mechanisms within the Standard Model (SM) is enough to generate the observed baryon asymmetry of the universe—an achievement that no other currently proposed mechanism can match. We use a Mesogenesis framework where the CP violation comes entirely from Standard Model contributions to neutral meson systems....
Motivated by the hint for time-dependent dynamical dark energy from an analysis of the DESI Baryon Accoustic Oscillation (BAO) data together with information from the Cosmic Microwave Background (CMB) and Supernovae (SN), we relax the assumption of a vanishing initial velocity for a quintessence field. In particular we focus on pseudo-Nambu-Goldstone-Boson (PNGB) quintessence in the form of an...
The observation of gravitational waves (GW) from dark sirens provides a novel measurement, complementary to other surveys that are electromagnetic (EM) signal–based. Under the assumption that both observations trace the distribution of matter up to some bias parameters, it is possible to infer cosmological parameters by cross-correlating their density maps.
As the number of resolved GW...
Gravitational particle production provides an ever-present background in non-thermal dark matter studies. I discuss the correspondence between the Starobinsky and Bogolyubov approaches to the problem of inflationary particle production, and derive strong constraints on frameworks with scalar dark relics.
(Based on D. Feiteira, O. Lebedev, arXiv:2503.14652)
In this talk I discuss the constraints imposed by BBN and CMB observations on primordial lepton flavour asymmetries with (approximately) vanishing total lepton number. I show that solving the momentum averaged quantum kinetic equations describing neutrino oscillations and interactions is an accurate approximation to the full momentum-dependent system, and the results reveal a rich flavour...
Cosmological phase transitionscan give rise to intriguing phenomena, such as baryogenesis or a stochastic gravitational wave background, due to nucleation and percolation of vacuum bubbles in the primordial plasma. A key parameter for predicting these relics is the bubble wall velocity, whose computation relies onsolving the Boltzmann equations of the various speciesalong the bubble profile....
Axions and axion-like particles (ALPs) remain compelling dark matter (DM) candidates, provided that the associated Peccei-Quinn (PQ) symmetry breaking scale $f_a$ is sufficiently large to ensure cosmological stability. In this talk, I will explore a novel framework in which ALPs possess flavor-violating (FV) couplings to Standard Model (SM) quarks, allowing them to be produced via freeze-in in...
Multiple axions may emerge in the low-energy effective theory of Nature. Generically, the potentials describing these axion fields are non-diagonal, such that a QCD axion might mix with one or more other axion-like-particles. QCD instanton effects render mixing between such states temperature-dependent. We explore how this mass-mixing can impact dark matter production through the misalignment...
In this work, we study the cosmological implications of an initial displacement of the Peccei-Quinn breaking field generated during inflation and the subsequent oscillations of the field around its minimum. These oscillations induce a parametric resonance effect, leading to the exponential growth of perturbations. In our analysis, we employ lattice simulations to investigate the abundance of...
Electromagnetic fields of pulsars can source coherent axion signals at their rotational frequencies, which can be detected by laboratory experiments—pulsarscopes. As a promising case study, we model axion emission from the well-studied Crab pulsar, which would yield a signal at $f \approx 29.6$ Hz and be present regardless of whether the axion contributes to the dark matter abundance. We...
The axion is a hypothetical particle first proposed by Peccei, Quinn, Weinberg and Wilczek to solve the strong CP problem. It was later realized that ultra-relativistic (or "hot") axions thermally produced in the early Universe can contribute measurably to the energy density of the Universe as dark radiation.
The effective number of neutrinos Neff, parametrizing this dark radiation fraction...
In modern cosmology, it is generally assumed that after inflation, the energy of the inflaton field is transferred to radiation through a process known as reheating.
axion-like particle (ALP) have recently gained attention as potential inflaton candidates, as they naturally preserve the flatness of the inflaton potential due to their shift symmetry.
In our work, we explore the reheating...
Axions and Axion-Like-Particles (ALPs) are theoretically well-motivated candidates for dark matter that, due to their large occupation number, can be described as oscillating classical fields. These particles may feature a quadratic interaction with ordinary matter which can modify the field's dynamics in the vicinity of such objects, inducing a very interesting phenomenology. In this talk, I...
Flavor deconstruction refers to a framework where the three fermion families are charged under non-universal gauge groups. Such Standard Model extensions have been proven to be capable of explaining flavor hierarchies among charged fermions. Recently, it has been shown that also neutrino anarchy can be realized within flavor-deconstructed models exploiting a seesaw mechanism. The present work...
A novel approach to neutrino oscillations is presented, which is analogous to birefringence. Neutrinos propagate as massless waves undergoing coherent forward flavour changing scattering off the quantum vacuum. The resulting coherent wave obeys a flavour mixing wave equation leading to; the standard oscillation probabilities, a universal effective refractive mass and a unique group velocity...
The study on lepton flavour violating (LFV) decays in the framework of the non-universal $Z'$ model delves into several fascinating aspects of particle physics. Focusing on the $\Sigma_b$ decays, which are induced by the quark-level transition $b \rightarrow s l_1l_2$, is especially relevant given the existing experimental constraints on LFV processes. The lepton flavour violating decays are...
Axion-like particles (ALPs) are hypothetical pseudoscalar states that emerge as pseudo-Nambu-Goldstone bosons from the breaking of an approximate global $ U(1) $ symmetry. They appear in several extensions of the Standard Model, offering potential solutions to the strong CP problem, the muon $ g-2 $ anomaly, neutrino mass generation, and dark matter. While most collider-based studies focus on...
We illustrate the potential of a future high-intensity $e^+e^-$ collider running at the $Z$ pole in probing extensions of the Standard Model via precise measurements of flavor-changing processes. We illustrate this potential both within effective field theories and simplified models inspired by current $B$-physics data, focusing on selected flavor-physics measurement projections at FCC-ee, and...
In recent times there has been a growing interest in the search for Axion-Like Particles (ALPs), as well as dedicated data analyses to identify potential evidence of New Physics compatible with an ALP, resulting in constraints on the ALP parameter space. Therefore, it is now the time to present a tool, ALPaca, that facilitates the combination among the different information on ALP...
Even though a fourth chiral generation of fermions is experimentally ruled out, the possibility of extending the SM with vector-like quarks (VLQs), where both chiral components transform the same way under SU(2)_L cannot be excluded. In particular, extensions of the SM involving isodoublet vector-like quarks with standard charges currently stand as the favoured candidate in explaining the...
Composite dark matter models, where dark matter exists in bound states formed in the early universe, have long been a source of scientific interest. In this talk, I will focus on loosely bound dark matter composite states, where the binding energy per constituent is small compared to the constituent’s bare mass. If this binding energy is sufficiently small, scattering with Standard Model...
Models of Sub-GeV dark matter coupled to a dark photon with kinetic mixing feature a rich phenomenology. They are thus constrained by a number of laboratory, astrophysical and cosmological observations. The biggest obstacle for fermionic DM particles to make up all of the observed DM comes from the strong constraints placed by the CMB and X-ray emission on DM annihilation. This can be overcome...
In this talk, we present a tuning of PYTHIA and a coalescence model that leads to realistic predictions of antinuclei production. This tuning is validated against LEP data including the fragmentation function of $b$-quarks into into $b$-hadrons, which is crucial for determining the $\bar{\Lambda}_b^0$ multiplicity. The coalescence model is tuned to ALICE data for the $\overline{\text{D}}$ and...
Ultra-heavy dark matter is a class of candidates for which direct detection experiments are ineffective due to the suppressed dark matter flux. We explore the potential of large underwater acoustic arrays, developed for ultra-high energy neutrino detection, to detect ultra-heavy dark matter. As ultra-heavy dark matter traverses seawater, it deposits energy through nuclear scattering,...
In this work, we propose a novel indirect detection signature of dark matter (DM) associated with the exceptionally bright gamma-ray burst GRB 221009A. Within our scenario, singlet scalar DM particles, produced at the redshift of the GRB, are up-scattered by high-energy cosmic rays (HECRs) during their journey to Earth. These highly boosted DM particles subsequently decay dominantly into...
We have presented a cosmological model of the Universe in $f(Q)$ gravity which shows the accelerating behavior. First the modified Friedmann equations have been reformulated into a system of coupled differential equations in order to ensure that the minimal set of equations required for a second-order gravity theory. These equations are then solved numerically. To constrain the parameters...
While electromagnetic couplings of UltraLight Dark Matter (ULDM) are the object of a wide range of experimental searches, there is no reason to believe that this is the only interaction of ULDM with the SM. In particular, the coupling with the SM weakly-interacting sector --neutrinos-- is much more unconstrained and leads to rich phenomenology.
In this talk, we present the results from a...
The discovery of neutrino oscillations and masses provides strong motivation to extend the Standard Model by including right-handed neutrinos, which lead to heavy neutrino states that could exist at the electroweak scale. These states may also be influenced by new high-scale, weakly interacting physics. Incorporating right-handed neutrinos into an effective field theory framework -the...
Neutrons constitute a major background in direct dark matter searches, yet previous measurements at LNGS have reported notable discrepancies in both flux values and energy spectra. These inconsistencies arise from variations in detector technologies, calibration methods, and energy windows used in different studies. Precise knowledge of this background is necessary to devise shielding and veto...
Composite dark matter models, where dark matter exists in bound states formed in the early universe, have long been a source of scientific interest. I will focus on loosely bound dark matter composite states, where the binding energy per constituent is small compared to the constituent’s bare mass. If this binding energy is sufficiently small, scattering with Standard Model nuclei will...
The non-observation of heavy particles at the LHC suggests the existence of an energy gap between collider scales and the scale of new physics. Therefore, Effective Field Theories (EFTs) provide a useful framework to describe BSM effects. The study of diboson production, $pp\to VW$, and associated Higgs production with a vector boson $pp\to Vh$, where $V=Z,W$, provides powerful probes of EFTs...
In this study, we explore the dynamics of mixed dark matter scenarios, focusing on the interplay between cold dark matter (CDM) and warm dark matter (WDM) components. Utilizing perturbation theory techniques, we analyze the evolution of perturbations in a cosmological context where CDM constitutes the primary dark matter component, while WDM, characterized by a weakly interacting, thermally...
In this poster, I present a dark matter model that couples to the standard model through a one-loop interaction with neutrinos, where the mediator particles also generate neutrino masses. We perform a global fit that incorporates dark matter relic abundance, primordial nucleosynthesis, neutrino mass, collider and indirect detection constraints. Thanks to the loop suppression, large couplings...
Axion-like particles (ALPs) are hypothetical pseudoscalar states that emerge as pseudo-Nambu-Goldstone bosons from the breaking of an approximate global $ U(1) $ symmetry. They appear in several extensions of the Standard Model, offering potential solutions to the strong CP problem, the muon $g-\!2$ anomaly, neutrino mass generation, and dark matter. While most collider-based studies focus on...
Neutrino oscillation clearly establishes the evidence of physics beyond the Standard Model (BSM). The Long Baseline Program has probed the phenomenology of neutrinos to unprecedented accuracy [1]. Next generation experiments like DUNE can study the propagation of flavor eigenstates on curved spacetime [2]. Neutrino oscillation in a Core-Collapse supernova (CCSN) on the other hand has a huge...
Models of Sub-GeV dark matter coupled to a dark photon with kinetic mixing feature a rich phenomenology. They are thus constrained by a number of laboratory, astrophysical and cosmological observations. The biggest obstacle for fermionic DM particles to make up all of the observed DM comes from the strong constraints placed by the CMB and X-ray emission on DM annihilation. This can be overcome...
An effective Lagrangian is composed of all higher dimensional operators that are Lorentz singlets and invariant under the gauge symmetries of the theory, suppressed by powers of the cutoff. A challenging problem is the construction of the EFT operators, since the number of possibilities grows extremely fast. Furthermore, many of these operators are linearly dependent or can even be discarded,...
We introduce a new mechanism where we claim that the Charge-Parity (CP) violation from mechanisms within the Standard Model (SM) is enough to generate the observed baryon asymmetry of the universe—an achievement that no other currently proposed mechanism can match. We use a Mesogenesis framework where the CP violation comes entirely from Standard Model contributions to neutral meson systems....
In this talk I discuss the constraints imposed by BBN and CMB observations on primordial lepton flavour asymmetries with (approximately) vanishing total lepton number. I show that solving the momentum averaged quantum kinetic equations describing neutrino oscillations and interactions is an accurate approximation to the full momentum-dependent system, and the results reveal a rich flavour...
Ultra-heavy dark matter is a class of candidates for which direct detection experiments are ineffective due to the suppressed dark matter flux. We explore the potential of large underwater acoustic arrays, developed for ultra-high energy neutrino detection, to detect ultra-heavy dark matter. As ultra-heavy dark matter traverses seawater, it deposits energy through nuclear scattering,...
In many theoretical models, the observed matter-antimatter asymmetry originates from out-of-equilibrium decays and scatterings of heavy particles. In these scenarios, charge-parity (CP) symmetry violation arises perturbatively through the interference between tree-level and one-loop diagrams. As a result, the CP asymmetry, characterized by the parameter $\epsilon$, is suppresed by higher...
Pulsar Timing Arrays (PTAs) have gathered strong evidence for the existence of a Stochastic Gravitational Wave Background at nanohertz frequencies. A possible astrophysical explanation of the signal is the production of Gravitational Waves (GWs) from the merging of Supermassive Black Hole Binaries, but many different explanations, which invoke new physics beyond the Standard Model, have been...
In curved spacetime, neutrinos experience an extra contribution to their effective Hamiltonian from a four-fermion interaction induced by spacetime geometry, specifically by torsion. This interaction is parity-violating, non-universal, and diagonal in the mass basis, and thus causes neutrino mixing while propagating through a fermionic matter background. It can significantly influence neutrino...
Abstract :
In curved spacetime, neutrinos experience an extra contribution to their effective Hamiltonian from a four-fermion interaction induced by spacetime geometry, specifically by torsion. This interaction is parity-violating, non-universal, and diagonal in the mass basis, and thus causes neutrino mixing while propagating through a fermionic matter background. It can significantly...
A novel approach to neutrino oscillations is presented, which is analogous to birefringence. Neutrinos propagate as massless waves undergoing coherent forward flavour changing scattering off the quantum vacuum. The resulting coherent wave obeys a flavour mixing wave equation leading to; the standard oscillation probabilities, a universal effective refractive mass and a unique group velocity...
Flavor deconstruction refers to a framework where the three fermion families are charged under non-universal gauge groups. Such Standard Model extensions have been proven to be capable of explaining flavor hierarchies among charged fermions. Recently, it has been shown that also neutrino anarchy can be realized within flavor-deconstructed models exploiting a seesaw mechanism. The present work...
Among the few methods to probe the early Universe through the observation of primordial particles, one possibility remains relatively unexplored: the detection of high-energy neutrinos emitted shortly after the Big Bang, originating from the decay or annihilation of early-Universe relics.
We present a general study of this scenario. First, we emphasise that such neutrinos could exhibit...
Positronium (Ps), an exotic atom composed of an electron and a positron, is an ideal system for testing Quantum Electrodynamics (QED) and probing potential extensions of the Standard Model (SM), including dark matter candidates such as mirror matter. Mirror matter theories predict that ortho-positronium (o-Ps) could oscillate into an invisible mirror state, leading to deviations in its...
A recast is developed for a search for non-pointing, delayed photons originating from the decay of a neutral long-lived particle (LLP) produced via an effective coupling in Higgs decays within the ATLAS detector. The LLP decays in the inner detector, producing an invisible particle and the signal photon. The analysis includes a refined calculation of non-pointing parameters, taking into...
The matter-antimatter asymmetry of the Universe represents one of the main open questions in particle physics and cosmology. In this talk, we will present a novel realization of cold baryogenesis, a mechanism involving the formation and decay of Standard Model SU(2)-textures, that relies on the out-of-equilibrium dynamics during a strong first order electroweak phase transition. By performing...
A dense neutrino gas can exhibit collective flavor oscillations, driven by neutrino–neutrino forward scattering, which profoundly affect flavor evolution in core-collapse supernovae and the early Universe. While numerous studies have shown that a zero crossing in the difference of flavor distributions ($g_{\Gamma}$) of neutrinos determines the existence and character of instabilities, a...
Superradiance can cause the axion cloud around a rotating black hole to reach extremely high densities, and the decay of these axions can produce a powerful laser. The electric field of these lasers is strong enough that the Schwinger effect may become significant, resulting in the production of an electron-positron plasma. Here, I detail the dynamics between axion lasers and this...
We present a bottom-up approach to an effective theory that simultaneously explains the matter–antimatter asymmetry via leptogenesis, the dark matter relic abundance via freeze-in or freeze-out mechanisms, and neutrino masses via the Weinberg operator. We show that, in the minimal scenario, only two new particles and a single portal operator coupling the visible and dark sectors are sufficient...
Sterile neutrinos are a minimal extension of the Standard Model of particle physics and a promising candidate for dark matter if their mass is in the keV-range. After the completion of the neutrino mass measurement campaign, the Karlsruhe Tritium Neutrino experiment (KATRIN) will be equipped with a novel multi-pixel silicon drift detector array, the TRISTAN detector. It will be capable of...
Various asymmetry-generating mechanisms are typically based on underlying reactions, such as decays or scatterings. In this contribution, however, we emphasize the essential role of CP invariants, from which a complete list of asymmetry-generating processes can be systematically derived. As a demonstration, we consider an asymmetric dark matter model based on a discrete $\mathbb{Z}_3$...
Even though a fourth chiral generation of fermions is experimentally ruled out, the possibility of extending the SM with vector-like quarks (VLQs), where both chiral components transform the same way under SU(2)_L cannot be excluded. In particular, extensions of the SM involving isodoublet vector-like quarks with standard charges currently stand as the favoured candidate in explaining the...
