I will discuss recent developments on the determination of the cosmological bound on the QCD axion mass, and the challenges for a correct interpretation of future cosmological surveys.
Axion-like particles – ALPs – are predicted in many extensions of the Standard Model with a spontaneously broken symmetry. If ALPs exist in Nature, they leave interesting signatures at colliders and other experiments. In this talk, you will hear about new ideas to search for axion-like particles with GeV-scale masses. I will explain what we learn from these searches about ALP interactions with...
The microphysics of Dark Matter (DM) remains an open question in high energy physics and cosmology. Given the diversity of particles in the Standard Model (SM), it is plausible that DM is also composed of more than one type of particle organized in a “dark sector”. In case of inelastic or pseudo-Dirac DM, the dark sector consists of two nearly mass-degenerate states. These can participate in...
At the Institute for Nuclear Physics in Mainz the new electron accelerator MESA (Mainz Energy-recovery Superconducting Accelerator) will go into operation within the next years. MESA will provide intense electron beams for hadron and nuclear physics, as well as for light dark matter (LDM) searches. In this contribution, we will present the MAGIX and DarkMESA experiments at MESA. MAGIX, is a...
This talk argues that rare Z decays to a QCD-like dark sector provide unexplored opportunities to the LHC experiments. We present two distinct classes of ultraviolet completions of such Z portal, including a novel scenario featuring a light Z’ vector boson, which we show to be compatible with electroweak precision data. We then highlight the phenomenological signatures, focusing on the...
Inferring theory parameters starting from observed events is a difficult task in high energy physics. This becomes particularly troublesome when dealing with events whose observables are not precisely measured and we want to understand the inference capability of multiple experimental setups. As a representative scenario, we will consider the production of ALPs and their subsequent decay into...
Axions may well solve both, the Dark Matter and the strong CP problems.
If they really comprise the dark matter, there are good prospects to detect them in the near future.
Presently already some experiments based on cavities are taking data with a sensitivity that should
lead to an axion dark matter discovery, should their mass be in the "classical invisible axion mass range" around...
I will discuss electromagnetic signals generated by gravitational waves (GWs) and light axion dark matter in microwave cavity experiments. In our proposed setup we generate and detect a heterodyne signal. This idea has the potential to cover a factor of 100 in mass on the QCD line and an extra 15 orders of magnitude of unexplored ALPs parameter space. Two prototypes are currently being...
In order to make the small effects of feebly interacting particles as candidates for Dark Matter or mediators to a Dark Sector detectable, novel approaches are in demand. I will present the use of cold atoms as quantum sensors for particle physics questions. In particular, I will show how the rapidly advancing precision of atomic clocks constrains light new bosons and how they could be used...
Dark matter direct (and indirect) detection experiments usually can only deter-
mine a specific combination of a power of the coupling and the dark matter density. This is also true for axion haloscopes which are sensitive to the product g^2ρ, the combination of axion-photon coupling squared and the dark matter density. We show, that in the lucky case when we intersect with a so-called...
Axions and axion-like particles (ALPs) are among the most popular candidates that explain the origin of the mysterious dark matter. The most popular ALP production mechanism studied in the literature is the misalignment mechanism, where an ALP field with a quadratic or cosine potential has negligible kinetic energy initially, and it starts oscillating when its mass becomes comparable to the...
Coupling of axions or axion-like particles (ALPs) with photons may lead to photons escaping optically opaque regions by oscillating into ALPs. This phenomenon can be probed through the Light Shining through Wall (LSW) technique. While this LSW technique has been used previously in controlled laboratory settings to constrain the ALP-photon coupling ($g_{a\gamma}$), we show that this can also be...
We study the impact of renormalization group effects on QCD axion phenomenology. Focusing on the DFSZ model, we argue that the relevance of running effects for the axion couplings crucially depends on the scale where the heavier Higgs doublet, charged under the Peccei-Quinn symmetry, is integrated out. We study the impact of these effects on astrophysical and cosmological bounds as well as on...
Axions and axion-like-particles (ALPs) are characterized by their two-photon coupling, which entails so-called photon-ALP oscillations as photons propagate through a magnetic field. These oscillations lead to distinctive signatures in the energy spectrum of high-energy photons from astrophysical sources, allowing one to probe the existence of ALPs. In particular, photon-ALP oscillations will...
I will discuss some possible avenues to hunt for sub-GeV dark matter in the lab. Specifically, for dark matter in the MeV to GeV range, I will discuss the possibility of employing the so-called Migdal effect in semiconductors. For dark matter in the keV to MeV range, instead, I will discuss the possibility of taking advantage of collective excitations in superfluid He-4 and anti-ferromagnets....
Dark matter particles with sub-GeV masses can be notoriously difficult to probe, because their typical momenta are insufficient to induce nuclear recoils above the thresholds of conventional direct detection experiments. In fact, it has repeatedly been claimed that even very strongly interacting dark matter could hide in this mass range, supposedly evading all observational bounds. In this...
In this talk, I will present a new model of DM where the DM is a composite of a spontaneously broken conformal field theory. The DM is a thermal relic with its abundance determined by the freeze-out of annihilations to dilatons, the Goldstone boson of broken conformal symmetry. If the dilaton is heavier than the DM this is an example of forbidden DM. I will present a fully realistic model that...
I will review our proposal to observe sub-GeV Dark Matter upscattered by cosmic rays at large neutrino detectors like Super- and Hyper-Kamiokande, DUNE, KamLAND and JUNO. I will show that this technique tests genuinely new parameter space, allowed both by theoretical consistency and by other direct detection experiments, cosmology, meson decays and the LHC. I will present novel strong...
In this talk, I will present updated constraints on 'light' dark matter (DM) particles with masses between 1 MeV and 5 GeV. In this range, we can expect DM-produced $e^\pm$ pairs to upscatter ambient photons in the Milky Way via Inverse Compton, and produce a flux of X-rays that can be probed by a range of space observatories. Using diffuse X-ray data from XMM-Newton, INTEGRAL, NuSTAR and...
DM direct detection experiments and the interpretation of their results are sensitive to the velocity structure of the galactic halo. However, the halo model is subject to large uncertainties. In this talk I will present a formalism to analyze DM-electron scattering events in semiconductor experiments without assuming a particular DM velocity distribution. Using simulated data, I will show...
The XENONnT experiment is a low-background dual phase liquid xenon Time Projection Chamber (TPC) with 5.9 tonnes of instrumented liquid xenon. Improved liquid xenon purification and radon distillation system along with various background mitigation strategies brought the electronic recoil backgrounds down to an unprecedented low of (15.8 ± 1.3) events/(keV · t · y) below recoil energies of 30...
The DarkSide experiment is a direct dark matter search using dual-phase argon time projection chamber. Its preceding experiment, DarkSide-50, produced world-class result for light dark matter search based on a low-threshold electron-counting measurement. A new proposed detector, DarkSide-LowMass, is optimized for such measurement based on the success of the DarkSide-50 and progress towards the...
Dark Matter has eluded us for decades and continues to do so. Currently lepton colliders provide exclusion limits on individual dark matter models, but many models may have either identical or indistinguishable signals. Hence there is a need for new methods or observables to determine the nature of the dark matter, especially if more than one candidate is present. Using $ e^+ e^-$ processes...
NANOGrav, the North American Nanohertz Observatory for Gravitational Waves, recently announced compelling evidence for the existence of a stochastic gravitational-wave background at nanohertz frequencies. This signal may either be of astrophysical origin and stem from a population of supermassive black-hole binaries, or of cosmological origin, reaching us from the early Universe. In this talk,...
The exquisite capabilities of liquid Argon Time Projection Chambers make them ideal to search for weakly interacting particles in Beyond the Standard Model scenarios. Given their location at CERN the ProtoDUNE detectors may be exposed to a flux of such particles, produced in the collisions of 400 GeV protons (extracted from the Super Proton Synchrotron accelerator) on a target. Here we point...
NA64 is a fixed target experiment at CERN searching for dark sectors in the scattering of electron, positron and muons on a target. In this talk, we report its latest results on sub-GeV Dark Matter searches with the 2016-2022 statistics (arXiv:2307.02404). With the new data, NA64 is starting to probe for the first time the very interesting region of parameter space motivated by benchmark light...
The constituents of dark matter are still unknown, and the viable possibilities span a very large mass range. Specific scenarios for the origin of dark matter sharpen the focus on a narrower range of masses: the natural scenario where dark matter originates from thermal contact with familiar matter in the early Universe requires the DM mass to lie within about an MeV to 100 TeV. Considerable...
A popular model for light (sub-GeV) Dark Matter (DM) is that its constituents belong to a Hidden Sector, uncharged under the Standard Model (SM) forces, and coupled to the SM through a new force carrier. In particular, theoretically well-motivated models propose the existence of a new U(1) light gauge boson, called the heavy (or dark) photon A’ which kinetically mixes with the SM photon. The...
The proposed LUXE experiment (LASER Und XFEL Experiment) at DESY, Hamburg, using the electron beam from the European XFEL, aims to probe QED in the non-perturbative regime created in collisions between high-intensity laser pulses and high-energy electron or photon beams. This setup also provides a unique opportunity to probe physics beyond the standard model. In this talk we show that by...
Many Dark Sector models contain photon-coupled long-lived particles. An outstanding example is an axion-like particle decaying into two photons. The forward physics detectors at the LHC, e.g., FASER, were shown to be particularly suitable for hunting ~sub-GeV ALPs thanks to numerous photons produced in pp collisions, which in turn are efficiently converted into ALPs by the Primakoff...
The idea that new physics could take the form of feebly interacting particles (FIPs) - particles with a mass below the electroweak scale, but which may have evaded detection due to their tiny couplings or very long lifetime - has gained a lot of traction in the last decade. Numerous experiments have been proposed to search for such particles. It is important, and now very timely, to...
Our efforts in searching for hints of new physics require close attention to the signatures of light particles arising in theories beyond the Standard Model (BSM) physics, as they could have eluded our searches. In many theories, these light BSM particles can have long lifetimes and are worth exploring. We focus on light long-lived particles (LLPs) coming from the decay of the discovered Higgs...
Nuclear beta and electron capture (EC) decay serve as sensitive probes of the structure and symmetries of the charged weak force between quarks and leptons. As such, precision measurements of the final-state products in these processes can be used as powerful laboratories to search for new physics from the meV to TeV scale. Significant advances in rare isotope availability and quality,...
Sterile neutrinos with keV-scale masses are popular candidates for warm dark matter. In the most straightforward case, they are produced via oscillations with active neutrinos. We focus on mixing with electron neutrinos and antineutrinos, which is object of test in several upcoming or running experiments like TRISTAN, ECHo, and HUNTER. We introduce effective self-interactions of active...
After the first observation of coherent elastic neutrino-nucleus scattering (CE$\nu$NS), further experiments with different technologies have been established and the question arises how this signal can be further exploited for a variety of investigations in the future. In this context, nuclear reactors with their intense emission of low-energy antineutrinos in combination with high-purity...
I will briefly review the old story of relic neutrinos and their potential role in cosmology and in particle physics, the state of the art in experimental searches for them and possible steps forward as I see them
The identity of neutrinos, Dirac or Majorara, is an essential yet unsolved puzzle of nature. By assuming that neutrinos are Dirac particles, we propose a light Dirac neutrino portal dark matter scenario which is based on the possible correlation between the relic right-handed neutrinos and present dark matter abundance. We studied the connection between dark matter and the light right-handed...
Dark Matter (DM) existence is a milestone of the cosmological standard model and, yet, its discovery still remains a complete conundrum. In this talk, I will investigate a unique and original way to probe properties of light dark matter candidates, exploiting the nature of the cosmic-ray (CR) transport inside starburst nuclei (SBNs). Indeed, SBNs are considered CR reservoirs, trapping them for...
Galaxy formation in the first billion years mark a time of great upheaval in our cosmic history: the first sources of light in the Universe, these galaxies ended the 'cosmic dark ages' and produced the first photons that could break apart the hydrogen atoms suffusing all of space starting the process of cosmic reionization. At the forefront of astronomical research, the past few years have...
I will talk about the two most prominent tensions of the LCDM model of cosmology, the Hubble Tension and the Large-Scale Structure (LSS) Tension. Both emerge between early and late universe data sets, yet no new single new physics explanation is able to address both successfully. An epoch of Early Dark Energy is a promising hypothesis that can resolve the Hubble tension but has been shown to...
Neutrinos are ubiquitous in cosmology and they represent a relevant component of the energy density of the Universe across its entire history. This fact makes cosmology a key arena to understand the properties of the most elusive particles in the Standard Model. I will review the main cosmological implications of neutrinos including their impact on Big Bang Nucleosynthesis and the Cosmic...
If the dark sector interacts with the visible one only through gravitational interactions, precision cosmology might be our best tool to test its dynamics. As a first step in this direction, we investigate the imprints of new long range forces acting solely on dark matter. Accounting for the presence of dark fifth forces in the effective field theory of large scale structure we derive the...
The microphysics of dark matter remains a mystery, with current data only setting upper bounds on interaction cross sections, or lower bounds on the mass in the case of a thermal relic. Going to higher redshift and smaller scales will let us improve these bounds, but more importantly, may allow us to distinguish between models with otherwise similar signals. In particular, I will present a...
The observed dark matter relic abundance may be explained by different mechanisms, such as thermal freeze-out/freeze-in, with one or more symmetric/asymmetric components. In this work we investigate the role played by asymmetries in determining the yield and nature of dark matter in non-minimal scenarios with more than one dark matter particle. In particular, we show that the energy density of...
The standard approach of calculating the relic density of thermally produced dark matter based on the assumption of kinetic equilibrium is known to fail for forbidden dark matter models since only the high momentum tail of the dark matter phase space distribution function contributes significantly to dark matter annihilations. Furthermore, it is known that the computationally less expensive...
We study the production of Dark Matter (DM) in a minimal freeze-in model during inflationary reheating. We analyze the case where a heavier parent particle decays into DM and a Standard Model fermion in two reheating scenarios: bosonic reheating (BR) and fermionic reheating (FR). Firstly, we show that for low reheating temperatures, BR and FR scenarios predict different lifetimes and masses...
