Dark Particles Research Articles

The primordial black holes that disappeared: connections to dark matter and MHz-GHz gravitational Waves

In the post-LIGO era, there has been a lot of focus on primordial black holes (PBHs) heavier than ∼ 1015g as potential dark matter (DM) candidates. We point out that the branch of the PBH family that disappeared — PBHs lighter than ∼ 109g that ostensibly Hawking evaporated away in the early Universe — also constitute an interesting frontier for DM physics. Hawking evaporation itself serves as a portal through which such PBHs can illuminate new physics, for example by emitting dark sector particles. Taking a simple DM scalar singlet model as a template, we compute the abundance and mass of PBHs that could have provided, by Hawking evaporation, the correct DM relic density. We consider two classes of such PBHs: those originating from curvature perturbations generated by inflation, and those originating from false vacuum collapse during a first-order phase transition. For PBHs of both origins we compute the gravitational wave (GW) signals emanating from their formation stage: from second-order effects in the case of curvature perturbations, and from sound waves in the case of phase transitions. The GW signals have peak frequencies in the MHz-GHz range typical of such light PBHs. We compute the strength of such GWs compatible with the observed DM relic density, and find that the GW signal morphology can in principle allow one to distinguish between the two PBH formation histories.

The new formulation of higgs effective field Theory

We present the explicit construction of the effective field theory (EFT) of standard model mass eigenstates. The EFT, which is invariant under U(1)e.m.× SU(3)c, is constructed based on the on-shell method and Young Tableau technique. This EFT serves as a new formulation of the Higgs EFT (HEFT), which can describe the infrared effects of new physics at the electroweak symmetry-breaking phase with greater conciseness. The current HEFT operator basis has a clear physical interpretation, making it more accessible for research in phenomenology. A complete list of HEFT operator bases for any-point vertices up to any dimension could be provided, and three- and four-point bases are provided as examples. Additionally, this framework realized as Mathematica program can be used to construct the EFT of any type of dark matter or particles with any spin.

DM-SM interactions mediated by spin-one particles: EFT study

Standard model-dark matter particles, mediated by spin one fields, are analyzed within the effective field theory framework. We [1, 2] consider dark particles masses from few MeV to 6.4 TeV. We restrict the EFT using bounds from relic density, Z invisible decay width, direct and indirect detection limits and collider constraints. Solutions below mZ are found for two operators. Others, around the electroweak scale or slightly above, are also compatible with all present limits.

Probing the Dark Sector with Nuclear Transition Photons.

Here we present world-leading sensitivity to light (<170 MeV) dark matter (DM) using beam-dump experiments. Dark sector particles produced during pion decay at accelerator beam dumps can be detected via scattering in neutrino detectors. The decay of nuclei excited by the inelastic scattering of DM is an unexploited channel which has significantly better sensitivity than similar searches using the elastic scattering channel. We show that this channel is a powerful probe of DM by demonstrating sensitivity to the thermal relic abundance benchmark in a scalar DM dark-photon portal model. This is achieved through the use of existing data, obtained by the KARMEN experiment over two decades ago, which allow us to set world-leading constraints on this model over a wide mass range. With experimental improvements planned for the future, this technique will be able to probe the thermal relic benchmark for fermionic DM across a wide mass range.

Non-Local Interactions Are Essential Elements for Dark Matter Halo Stability: A Cross-Model Study

This paper introduces a comprehensive methodology for examining the stability of dark matter (DM) halos, emphasizing the necessity for non-local inter-particle interactions, whether they are fundamental or effective in nature, to maintain halo stability. We highlight the inadequacy of vanilla cold, collisionless DM models in forecasting a stable halo without considering a “non-local” interaction in the halo’s effective free energy, which could potentially arise from factors like baryonic feedback, self-interactions, or the intrinsic quantum characteristics of dark particles. The stability prerequisite necessitates significant effective interactions between any two points within the halo, regardless of their distance from the center. The methodology proposed herein offers a systematic framework to scrutinize the stability of various DM models and refine their parameter spaces. We deduce that DM halos within a model, where the deviation from the standard cold, collisionless framework is confined to regions near the halo center, are unlikely to exhibit stability in their outer sectors. In our study, we demonstrate that the issue of instability within DM halos cannot be addressed adequately using perturbative quantum effects. This issue is less pronounced for fermionic DM but suffers from a higher degree of severity when considering bosonic DM. We find that halos made of bosons with notable quantum effects have sharp edges, while those made of fermions show more diffuse boundaries extending toward infinity. To present the potentials of the cross-model approach, we explore the broadest form of the effective free energy around a chosen mass profile. Next, as a case study, we employ a model where the deviation from the standard cold, collisionless DM model is represented by a two-body interaction in the effective free energy to show how to use observations to investigate universal classes of DM models.

Exploring mirror twin Higgs cosmology with present and future weak lensing surveys

We explore the potential of precision cosmological data to study non-minimal dark sectors by updating the cosmological constraint on the mirror twin Higgs model (MTH). The MTH model addresses the Higgs little hierarchy problem by introducing dark sector particles. In this work, we perform a Bayesian global analysis that includes the latest cosmic shear measurement from the DES three-year survey and the Planck CMB and BAO data. In the early Universe, the mirror baryon and mirror radiation behave as dark matter and dark radiation, and their presence modifies the Universe's expansion history. Additionally, the scattering between mirror baryon and photon generates the dark acoustic oscillation process, suppressing the matter power spectrum from the cosmic shear measurement. We demonstrate how current data constrain these corrections to the ΛCDM cosmology and find that for a viable solution to the little hierarchy problem, the proportion of MTH dark matter cannot exceed about 30% of the total dark matter density, unless the temperature of twin photon is less than 30% of that of the standard model photon. While the MTH model is presently not a superior solution to the observed H 0 tension compared to the ΛCDM+ΔN eff model, we demonstrate that it has the potential to alleviate both the H 0 and S 8 tensions, especially if the S 8 tension persists in the future and approaches the result reported by the Planck SZ (2013) analysis. In this case, the MTH model can relax the tensions while satisfying the DES power spectrum constraint up to k ≲ 10 hMpc-1. If the MTH model is indeed accountable for the S 8 and H 0 tensions, we show that the future China Space Station Telescope (CSST) can determine the twin baryon abundance with a 10% level precision.

W boson mass in singlet-triplet scotogenic dark matter model

The recent high precision measurement of [Formula: see text] boson mass by CDF-II collaboration points to the contribution(s) of new physics beyond the Standard Model (SM). One of the minimalistic ways to account for the anomalous [Formula: see text] boson mass is by introducing a hyperchargeless real [Formula: see text] triplet scalar whose vacuum expectation value (VEV) explicitly contributes to the [Formula: see text] boson mass at the tree level while the [Formula: see text] boson mass remains the same. Such a triplet can be naturally embedded in a singlet-triplet scotogenic model for one-loop neutrino mass generated by dark sector particles running in the loop. We discuss the detailed phenomenology of the model, obtaining the parameter space consistent with the CDF-II [Formula: see text] boson mass measurements. The dark matter as well as the constraints comings from [Formula: see text], [Formula: see text], [Formula: see text] parameters are also analyzed.

Dark matter bound states: A window into the early universe

Despite significant experimental sensitivity to point-like, weakly interacting particles at the electroweak mass scale, dark matter has not been found yet. This could hint at a more complex dark sector with multiple states or composite dark particles, much like the complexity of the standard model. Currently, our experimental sensitivity to such scenarios is limited by a lack of theoretical understanding. The investigation of Dark Matter systems with unstable or stable bound states provides a playground that leads to the development of important tools needed for the understanding of dark sectors with complex phenomena and allows to experimentally test well-motivated DM scenarios.

Ultra-light axions and the S 8 tension: joint constraints from the cosmic microwave background and galaxy clustering

We search for ultra-light axions as dark matter (DM) and dark energy particle candidates, for axion masses 10-32 eV ≤ m a ≤ 10-24 eV, by a joint analysis of cosmic microwave background (CMB) and galaxy clustering data — and consider if axions can resolve the tension in inferred values of the matter clustering parameter S 8. We give legacy constraints from Planck 2018 CMB data, improving 2015 limits on the axion density Ωa h 2 by up to a factor of three; CMB data from the Atacama Cosmology Telescope and the South Pole Telescope marginally weaken Planck bounds at m a = 10-25 eV, owing to lower (and theoretically-consistent) gravitational lensing signals. We jointly infer, from Planck CMB and full-shape galaxy power spectrum and bispectrum data from the Baryon Oscillation Spectroscopic Survey (BOSS), that axions are, today, < 10% of the DM for m a ≤ 10-26 eV and < 1% for 10-30 eV ≤ m a ≤ 10-28 eV. BOSS data strengthen limits, in particular at higher m a by probing high-wavenumber modes (k < 0.4h Mpc-1). BOSS alone finds a preference for axions at 2.7σ, for m a = 10-26 eV, but Planck disfavours this result. Nonetheless, axions in a window 10-28 eV ≤ m a ≤ 10-25 eV can improve consistency between CMB and galaxy clustering data, e.g., reducing the S 8 discrepancy from 2.7σ to 1.6σ, since these axions suppress structure growth at the 8h -1 Mpc scales to which S 8 is sensitive. We expect improved constraints with upcoming high-resolution CMB and galaxy lensing and future galaxy clustering data, where we will further assess if axions can restore cosmic concordance.

Dark matter produced from right-handed neutrinos

Right-handed neutrinos (RHNs) provide a natural portalto a dark sector accommodating dark matter (DM). In this work, weconsider that the dark sector is connected to the standard modelonly via RHNs and ask how DM can be produced from RHNs. Our frameworkconcentrates on a rather simple and generic interaction that couplesRHNs to a pair of dark particles. Depending on whether RHNs are lightor heavy in comparison to the dark sector and also on whether oneor both of them are in the freeze-in/out regime, there are many distinctscenarios resulting in rather different results. We conduct a comprehensiveand systematic study of all possible scenarios in this paper. Forillustration, we apply our generic results to the type-I seesaw modelwith the dark sector extension, addressing whether and when DM inthis model can be in the freeze-in or freeze-out regime. Some observationalconsequences in this framework are also discussed.

A trial of filter cake pellets and bagasse co–combustion in a sugar mill steam generator: Thermal and economical assessments

Filter cake is a by-product from sugar production and estimated to be 4% of input sugarcane. The filter cake is a dark brown fine particle with 65%–75% moisture content. It is estimated to be 4 million ton/year in Thai sugar industry. This research shows a concept of turning this waste to energy by pelletisation and using the pellets as fuel in a steam generator. The pellets were co-combusted with bagasse in different ratios, i.e., 1%, 3% and 5% by mass. Combustion efficiency, outlet steam pressure and temperature were compared with the case of 100% bagasse. The results showed that 1% and 3% filter cake pellets gave approximately 91% combustion efficiency which is similar to the case of pure bagasse. However, when using 5% pellets the combustion efficiency dropped to 87% due to feeding system problem. It was suggested that fuel spreading system must be modified when using 5% or higher ratio of the pellets. Moreover, outlet steam temperature and pressure were almost the same for the case of pure bagasse compared with the case of 1% and 3% pellets co-combustion. It reveals that filter cake pellets can be utilised as fuel without any problem, and this is a way to support the zero-waste campaign in sugar industry.

The Quest for the Nature of the Dark Matter: The Need of a New Paradigm

The phenomenon of the Dark matter baffles the researchers: the underlying dark particle has escaped so far the detection and its astrophysical role appears complex and entangled with that of the standard luminous particles. We propose that, in order to act efficiently, alongside with abandoning the current ΛCDM scenario, we need also to shift the Paradigm from which it emerged.

Distinct signatures of spinning PBH domination and evaporation: doubly peaked gravitational waves, dark relics and CMB complementarity

Ultra-low mass primordial black holes (PBH), which may briefly dominate the energy density of the universe but completely evaporate before the big bang nucleosynthesis (BBN), can lead to interesting observable signatures. In our previous work, we studied the generation of a doubly peaked spectrum of induced stochastic gravitational wave background (ISGWB) for such a scenario and explored the possibility of probing a class of baryogenesis models wherein the emission of massive unstable particles from the PBH evaporation and their subsequent decay contributes to the matter-antimatter asymmetry. In this work, we extend the scope of our earlier work by including spinning PBHs and consider the emission of light relativistic dark sector particles, which contribute to the dark radiation (DR) and massive stable dark sector particles, thereby accounting for the dark matter (DM) component of the universe. The ISGWB can probe the non-thermal production of these heavy DM particles, which cannot be accessible in laboratory searches. For the case of DR, we find a novel complementarity between the measurements of ∆Neff from these emitted particles and the ISGWB from PBH domination. Our results indicate that the ISGWB has a weak dependence on the initial PBH spin. However, for gravitons as the DR particles, the initial PBH spin plays a significant role, and only above a critical value of the initial spin parameter a*, which depends only on initial PBH mass, the graviton emission can be probed in the CMB-HD experiment. Upcoming CMB experiments such as CMB-HD and CMB-Bharat, together with future GW detectors like LISA and ET, open up an exciting possibility of constraining the PBHs parameter space providing deeper insights into the expansion history of the universe between the end of inflation and BBN.

Heavy neutral leptons at beam dump experiments of future lepton colliders

A new beam dump experiment that utilizes the beam of future high energy electron-positron colliders could be an excellent avenue to search for dark sector particles due to its unprecedented high energy and intensity. We consider heavy neutral leptons (HNLs) as a specific example to demonstrate the sensitivity of searches for dark sector particles at future electron-positron collider beam dump experiments. This includes the study of the reach at the International Linear Collider (ILC), the Cool Copper Collider (C3), and the Compact Linear Collider (CLIC). We comprehensively examine the HNL production and detector acceptance at these electron beam dump experiments. We show that these experiments will probe regions of HNL parameter space, not yet probed by past experiments, as well as by future approved experiments. Our study also motivates a more detailed analysis of heavy meson productions in high-energy electron-nucleon collisions in thick targets.

Dark matter effects on hybrid star properties

In the present work, we investigate the effects of dark matter (DM) on hybrid star properties. We assume that dark matter is mixed with both hadronic and quark matter and interacts with them through the exchange of a Higgs boson. The hybrid star properties are obtained from equations of state calculated with a Maxwell prescription. For the hadronic matter, we use the NL3* parameter set, and for the quark matter, the MIT bag model with a vector interaction. We see that dark matter does not influence the phase transition points (pressure and chemical potential) but shifts the discontinuity on the energy density, which ultimately reduces the minimum mass star that contains a quark core. Moreover, it changes considerably the star family mass-radius diagrams and moves the merger polarizability curves inside the confidence lines. Another interesting feature is the influence of DM in the quark core of the hybrid stars constructed. Our results show an increase of the core radius for higher values of the dark particle Fermi momentum.

Dark matter production through a non-thermal flavon portal

The Froggatt-Nielsen (FN) mechanism provides an attractive way of generating the determined fermion mass hierarchy and quark mixing matrix elements in the Standard Model (SM). Here we extend it by coupling the FN field, the flavon, to a dark sector containing one or more dark matter particles which are produced non-thermally sequentially through flavon production. Non-thermal flavon production occurs efficiently via freeze-in and through field oscillations. We explore this in the regime of high-scale breaking Λ of the global U(1)FN group and at the reheating temperature TR ≪ Λ where the flavon remains out of equilibrium at all times. We identify phenomenologically acceptable regions of TR and the flavon mass where the relic abundance of dark matter and other cosmological constraints are satisfied. In the case of one-component dark matter we find an effective upper limit on the FN charges at high Λ, i.e. {Q}_{textrm{FN}}^{textrm{DM}}le 13 . In the multi-component dark sector scenario the dark matter can be the heaviest dark particle that can be effectively stable at cosmological timescales, alternatively it can be produced sequentially by decays of the heavier ones. For scenarios where dark decays occur at intermediate timescales, i.e. t ~ 0.1 − 1028 s, we find that existing searches can effectively probe interesting regions of parameter space. These searches include indirect probes on decays such as γ-ray and neutrino telescopes as well as analyses of the Cosmic Microwave Background, as well as constraints on small scale structure formation from the Lyman-α forest. We comment on the future prospects of such probes, place projected sensitivities, and discuss how this scenario could accommodate the cosmological S8 tension.

Search for the Pair Production of Dark Particles X with K_{L}^{0}→XX, X→γγ.

We present the first search for the pair production of dark particles X via K_{L}^{0}→XX with X decaying into two photons using the data collected by the KOTO experiment. No signal was observed in the mass range of 40-110 MeV/c^{2} and 210-240 MeV/c^{2}. This sets upper limits on the branching fractions as B(K_{L}^{0}→XX)<(1-4)×10^{-7} and B(K_{L}^{0}→XX)<(1-2)×10^{-6} at the 90%confidence level for the two mass regions, respectively.

Dark SU(2) Stueckelberg portal

We study the non-abelian $SU(2)_D$ extension of the $U(1)_D$ Stueckelberg portal, which plays a role of the mediator between the Standard Model (SM) and Dark Sector (DS). This portal is specified by the Stueckelberg mechanism for generation of dark gauge boson masses. Proposed $U(1)_D\times SU(2)_D$ Stueckelberg portal has a connection with SM matter fields in analogy with Familon Model. We derive bounds on the couplings of dark portal bosons and SM particles, which govern diagonal and non-diagonal flavor transitions of quarks and leptons.

FCNC B and K meson decays with light bosonic Dark Matter

We consider decays of B and K mesons into a pseudo-scalar or vector meson plus missing energy. Within the SM, these modes originate from flavor changing neutral current (FCNC) processes with two neutrinos in the final state. In this paper we consider the experimental upper bounds on these modes and interpret the difference between these bounds and the SM prediction as a window into new light invisible particles. In particular we consider the case where some new symmetry requires the new particles to be produced in pairs. We first construct the general low energy effective Lagrangian coupling an FCNC with two dark sector particles of spin zero, one-half and one. We then present numerical estimates for the constraints that can be placed on these interactions, finding that an effective new physics scale from mathcal{O} (10)- mathcal{O} (1011) GeV can be probed, with the exact value strongly depending on the interaction structure as well as the mass of the invisible particle. For we incorporate into our constraints the effect of using only the signal regions of NA62, and for the q2-dependent efficiency of Belle II.

Probing a light dark sector at future lepton colliders via invisible decays of the SM-like and dark Higgs bosons

A renormalizable UV model for axionlike particles or hidden photons, which may explain the dark matter, usually involves a dark Higgs field, which is a singlet under the standard model (SM) gauge group. The dark sector can couple to the SM particles via the portal coupling between the SM-like Higgs and dark Higgs fields. Through this coupling, the dark sector particles can be produced in either the early Universe or the collider experiments. Interestingly, not only the SM-like Higgs boson can decay into the light dark bosons, but also a light dark Higgs boson may be produced and decay into the dark bosons in a collider. In this paper, we perform the first collider search for invisible decays by taking both the Higgs bosons into account. We use a multivariate technique to best discriminate the signal from the background. We find that a large parameter region can be probed at the International Linear Collider operating at the center-of-mass energy of 250 GeV. In particular, even when the SM-like Higgs invisible decay is a few orders of magnitude below the planned sensitivity reaches of the International Linear Collider and the high luminosity LHC, the scenario can be probed by the invisible decay of the dark Higgs boson produced via a similar diagram. Measuring the dark Higgs boson decay into the dark sector will be a smoking gun signal of the light dark sector. A similar search of the dark sector would be expected in, e.g., the Cool Copper Collider, the Circular Electron Positron Collider, the Compact Linear Collider, and the Future Circular electron-positron Collider.