Dark Matter Coupling Research Articles

Clockworking FIMPs

We study freeze-in dark matter production in models that rely on the Clock-work mechanism to suppress the dark matter couplings to the visible sector. We construct viable scalar and fermionic dark matter models within this “Clockwork FIMP” scenario, with several subtleties that need to be taken into account revealed in the model-building process. We also provide analytic, semi-analytic and numerical results for the diagonalization of Clockwork-type mass matrices and briefly discuss the LHC phenomenology of the corresponding scenarios.

Violation of the equivalence principle from light scalar dark matter

In this paper, we study the local observational consequences of a violation of the Einstein Equivalence Principle induced by models of light scalar Dark Matter (DM). We focus on two different models where the scalar field couples linearly or quadratically to the standard model of matter fields. For both these cases, we derive the solutions of the scalar field. We also derive from first principles the expressions for two types of observables: (i) the local comparison of two atomic sensors that are differently sensitive to the constants of Nature and (ii) the local differential acceleration between two test-masses with different compositions. For the linear coupling, we recover that the signatures induced by DM on both observables are the sum of harmonic and Yukawa terms. For the quadratic coupling on the other hand, the signatures derived for both types of observables turn out to be a sum of a time independent term and of an harmonic oscillation, whose amplitudes both depend on the position. Such a behavior is new and can make experiments in space more sensitive than terrestrial ones. Besides, the observables present some interesting non-linear behaviors that are due to the amplification or to the screening of the scalar-field, depending on the parameters of the theory, and on the compactness of the source of the gravitational field. Finally, we infer the various limits on the DM coupling parameters by using existing frequency comparisons on the one hand and tests of the universality of free fall on the ground (torsion balances) or in space (MICROSCOPE mission) on the other hand. We show that in the quadratic case, so-called natural parameters are still allowed by observations.

PeV scale supersymmetry breaking and the IceCube neutrino flux

The observation of very high energy neutrino events at IceCube has grasped a lot of attention in the fields of both astrophysics and particle physics. It has been speculated that these high energy neutrinos might originate either from purely conventional astrophysical sources or from the late decay of a super heavy (PeV scale) dark matter (DM) particle. In order for decaying DM to be a dominant source of the IceCube high-energy neutrinos, it would require an unusually suppressed value of the coupling of DM to neutrinos. We attempt to explain this small coupling in the context of an R-parity conserving minimal supergravity model which has right-handed neutrino superfields. With the main assumptions of super-partner masses at the PeV scale and also a reheating temperature not much larger than the PeV scale, we find in our model several natural order-of-magnitude “miracles”, (i) the gravitino is produced via freeze-in as a DM candidate with the correct relic density (ii) the right-handed (RH) sneutrino makes up only a tiny fraction (10−6), of the present day energy density of the universe, yet its decay lifetime to the gravitino and neutrinos is such that it naturally predicts the right order-of-magnitude for the IceCube neutrino flux. The long lifetime of the RH sneutrino is explained by the existence of a global R-symmetry which is only broken due to supersymmetry breaking effects. Our model also predicts a flux of 100 TeV gamma rays from the decaying RH sneutrino which are within the current observational constraints.

Surrogate models for direct dark matter detection

In this work we introduce RAPIDD, a surrogate model that speeds up the computation of the expected spectrum of dark matter particles in direct detection experiments. RAPIDD replaces the exact calculation of the dark matter differential rate (which in general involves up to three nested integrals) with a much faster parametrization in terms of ordinary polynomials of the dark matter mass and couplings, obtained in an initial training phase. In this article, we validate our surrogate model on the multi-dimensional parameter space resulting from the effective field theory description of dark matter interactions with nuclei, including also astrophysical uncertainties in the description of the dark matter halo. As a concrete example, we use this tool to study the complementarity of different targets to discriminate simplified dark matter models. We demonstrate that RAPIDD is fast and accurate, and particularly well-suited to explore a multi-dimensional parameter space, such as the one in effective field theory approach, and scans with a large number of evaluations.

Search for narrow and broad dijet resonances in proton-proton collisions at sqrt{s}=13 TeV and constraints on dark matter mediators and other new particles

Searches for resonances decaying into pairs of jets are performed using proton-proton collision data collected at sqrt{s}=13 TeV corresponding to an integrated luminosity of up to 36 fb−1. A low-mass search, for resonances with masses between 0.6 and 1.6 TeV, is performed based on events with dijets reconstructed at the trigger level from calorimeter information. A high-mass search, for resonances with masses above 1.6 TeV, is performed using dijets reconstructed offline with a particle-flow algorithm. The dijet mass spectrum is well described by a smooth parameterization and no evidence for the production of new particles is observed. Upper limits at 95% confidence level are reported on the production cross section for narrow resonances with masses above 0.6 TeV. In the context of specific models, the limits exclude string resonances with masses below 7.7 TeV, scalar diquarks below 7.2 TeV, axigluons and colorons below 6.1 TeV, excited quarks below 6.0 TeV, color-octet scalars below 3.4 TeV, W′ bosons below 3.3 TeV, Z′ bosons below 2.7 TeV, Randall-Sundrum gravitons below 1.8 TeV and in the range 1.9 to 2.5 TeV, and dark matter mediators below 2.6 TeV. The limits on both vector and axial-vector mediators, in a simplified model of interactions between quarks and dark matter particles, are presented as functions of dark matter particle mass and coupling to quarks. Searches are also presented for broad resonances, including for the first time spin-1 resonances with intrinsic widths as large as 30% of the resonance mass. The broad resonance search improves and extends the exclusions of a dark matter mediator to larger values of its mass and coupling to quarks.

Z-pole test of effective dark matter diboson interactions at the CEPC

We investigate the projected sensitivity to effective dark matter (DM)–diboson interaction during the high luminosity Z-pole and 240 GeV runs at the proposed Circular Electron Positron Collider (CEPC). The proposed runs at the 91.2 GeV e^+e^- center of mass energy offers an interesting opportunity to probe effective dark matter couplings to the Z boson, which can be less stringently tested in non-collider searches. We investigate the prospective sensitivity for dimension 6 and dimension 7 effective diboson operators to scalar and fermion dark matter. These diboson operators can generate semi-visible Z boson decay, and high missing transverse momentum mono-photon signals that can be test efficiently at the CEPC, with a small and controllable Standard Model gamma bar{nu }nu background. Projected sensitivities for the effective gamma Z coupling efficient kappa _{gamma Z}< (1030,hbox {GeV})^{-3}, (1970,hbox {GeV})^{-3} for scalar DM, kappa _{gamma Z}< (360,text {GeV})^{-3}, (540,text {GeV})^{-3} for fermion DM are obtain for 25 hbox {fb}^{-1} and 2.5hbox {ab}^{-1}Z-pole luminosities assuming the optimal low dark matter mass range. We also compare the CEPC sensitivities to current direct and indirect search limits on these effective DM-diboson operators.

Common origin of dirac neutrino mass and freeze-in massive particle dark matter

Motivated by the fact that the origin of tiny Dirac neutrino masses via the standard model Higgs field and non-thermal dark matter populating the Universe via freeze-in mechanism require tiny dimensionless couplings of similar order of magnitudes (∼ 10−12), we propose a framework that can dynamically generate such couplings in a unified manner. Adopting a flavour symmetric approach based on A4 group, we construct a model where Dirac neutrino coupling to the standard model Higgs and dark matter coupling to its mother particle occur at dimension six level involving the same flavon fields, thereby generating the effective Yukawa coupling of same order of magnitudes. The mother particle for dark matter, a complex scalar singlet, gets thermally produced in the early Universe through Higgs portal couplings followed by its thermal freeze-out and then decay into the dark matter candidates giving rise to the freeze-in dark matter scenario. Some parts of the Higgs portal couplings of the mother particle can also be excluded by collider constraints on invisible decay rate of the standard model like Higgs boson. We show that the correct neutrino oscillation data can be successfully produced in the model which predicts normal hierarchical neutrino mass. The model also predicts the atmospheric angle to be in the lower octant if the Dirac CP phase lies close to the presently preferred maximal value.

Testing the Universality of Free Fall towards Dark Matter with Radio Pulsars.

The violation of the weak equivalence principle (EP) in the gravitational field of Earth, described by the Eötvös parameter η_{⊕}, was recently constrained to the level |η_{⊕}|≲10^{-14} by the MICROSCOPE space mission. The Eötvös parameter η_{DM}, pertaining to the differential couplings of dark matter (DM) and ordinary matter, was only tested to the level |η_{DM}|≲10^{-5} by the Eöt-Wash group and lunar laser ranging. This test is limited by the EP-violating driving force in the solar neighborhood that is determined by the galactic distribution of DM. Here we propose a novel celestial experiment using the orbital dynamics from radio timing of binary pulsars, and obtain a competing limit on η_{DM} from a neutron-star-white-dwarf (NS-WD) system, PSR J1713+0747. The result benefits from the large material difference between the NS and the WD and the large gravitational binding energy of the NS. If we can discover a binary pulsar within ∼10 pc of the galactic center, where the driving force is much larger in the expected DM spike, precision timing will improve the test of the universality of free fall towards DM and constrain various proposed couplings of DM to the standard model by several orders of magnitude. Such a test probes the hypothesis that gravity is the only long-range interaction between DM and ordinary matter.

Compatibility of a dark matter discovery at XENONnT or LZ with the WIMP thermal production mechanism

The discovery of dark matter (DM) at XENONnT or LZ would place constraints on DM particle mass and coupling constants. It is interesting to ask when these constraints can be compatible with the DM thermal production mechanism. We address this question within the most general set of renormalisable models that preserve Lorentz and gauge symmetry, and that extend the Standard Model by one DM candidate of mass $m_{\rm DM}$ and one particle of mass $M_{med}$ mediating DM-quark interactions. Our analysis divides into two parts. First, we postulate that XENONnT/LZ has detected $\mu_S\sim\mathcal{O}(100)$ signal events, and use this input to calculate the DM relic density, $\Omega_{DM} h^2$. Then, we identify the regions in the $M_{med} - \Omega_{DM} h^2$ plane which are compatible with the observed signal and with current CMB data. We find that for most of the models considered here, $\mathcal{O}(100)$ signal events at XENONnT/LZ and the DM thermal production are only compatible for resonant DM annihilations, i.e. for $M_{med}\simeq2 m_{DM}$. In this case, XENONnT/LZ would be able to simultaneously measure $m_{DM}$ and $M_{med}$. We also discuss the dependence of our results on $m_{DM}$, $\mu_S$ and the DM spin, and provide analytic expressions for annihilation cross-sections and mediator decay widths for all models considered in this study.

Searching for light dark matter through Positronium decay

A novel approach to detect light dark matter through the observation of a single photon in the decay of Positronium (Ps) is proposed. Branching ratio calculations indicate that light dark matter coupling to the Standard Model through a novel dark vector boson in the mass range m A ′ = 10–500 keV with strength ϵ = 2 × 10−5 –10−8 is well above the previously computed Standard Model background decay Ps → γ ν ν and could be sensitive to observation.

Weak mixing below the weak scale in dark-matter direct detection

If dark matter couples predominantly to the axial-vector currents with heavy quarks, the leading contribution to dark-matter scattering on nuclei is either due to one-loop weak corrections or due to the heavy-quark axial charges of the nucleons. We calculate the effects of Higgs and weak gauge-boson exchanges for dark matter coupling to heavy-quark axial-vector currents in an effective theory below the weak scale. By explicit computation, we show that the leading-logarithmic QCD corrections are important, and thus resum them to all orders using the renormalization group.

Scalar dark matter in leptophilic two-Higgs-doublet model

Two-Higgs-Doublet Model of Type-X in the large tan⁡β limit becomes leptophilic to allow a light pseudo-scalar A and thus provides an explanation of the muon g−2 anomaly. Introducing a singlet scalar dark matter S in this context, one finds that two important dark matter properties, nucleonic scattering and self-annihilation, are featured separately by individual couplings of dark matter to the two Higgs doublets. While one of the two couplings is strongly constrained by direct detection experiments, the other remains free to be adjusted for the relic density mainly through the process SS→AA. This leads to the 4τ final states which can be probed by galactic gamma ray detections.

Model-independent analysis of the DAMPE excess

The Dark Matter Particle Explorer (DAMPE) recently released measurements of the electron spectrum with a hint of a narrow peak at about 1.4 TeV. We investigate dark matter (DM) models that could produce such a signal by annihilation in a nearby subhalo whilst simultaneously satisfying constraints from DM searches. In our model-independent approach, we consider all renormalizable interactions via a spin 0 or 1 mediator between spin 0 or 1/2 DM particles and the Standard Model leptons. We find that of the 20 combinations, 10 are ruled out by velocity or helicity suppression of the annihilation cross section to fermions. The remaining 10 models, though, evade constraints from the relic density, collider and direct detection searches, and include models of spin 0 and 1/2 DM coupling to a spin 0 or 1 mediator. We delineate the regions of mediator mass and couplings that could explain the DAMPE excess. In all cases the mediator is required to be heaver than about 2 TeV by LEP limits.

Flavoured Dark Matter moving left

We investigate the phenomenology of a simplified model of flavoured Dark Matter (DM), with a dark fermionic flavour triplet coupling to the left-handed SU(2)L quark doublets via a scalar mediator. The DM-quark coupling matrix is assumed to constitute the only new source of flavour and CP violation, following the hypothesis of Dark Minimal Flavour Violation. We analyse the constraints from LHC searches, from meson mixing data in the K, D, and Bd,s meson systems, from thermal DM freeze-out, and from direct detection experiments. Our combined analysis shows that while the experimental constraints are similar to the DMFV models with DM coupling to right-handed quarks, the multitude of couplings between DM and the SM quark sector resulting from the SU(2)L structure implies a richer phenomenology and significantly alters the resulting impact on the viable parameter space.

Direct couplings of mimetic dark matter and their cosmological effects**Supported by NSFC (11422543, 11653002)

The original mimetic model was proposed to take the role of dark matter. In this paper we consider possible direct interactions of mimetic dark matter with other matter in the universe, especially standard model particles such as baryons and photons. By imposing shift symmetry, the mimetic dark matter field can only have derivative couplings. We discuss the possibilities of generating baryon number asymmetry and cosmic birefringence in the universe based on the derivative couplings of mimetic dark matter to baryons and photons.

Interacting dark sector and precision cosmology

We consider a recently proposed model in which dark matter interacts with a thermal background of dark radiation. Dark radiation consists of relativistic degrees of freedom which allow larger values of the expansion rate of the universe today to be consistent with CMB data (H0-problem). Scattering between dark matter and radiation suppresses the matter power spectrum at small scales and can explain the apparent discrepancies between ΛCDM predictions of the matter power spectrum and direct measurements of Large Scale Structure LSS (σ8-problem). We go beyond previous work in two ways: 1. we enlarge the parameter space of our previous model and allow for an arbitrary fraction of the dark matter to be interacting and 2. we update the data sets used in our fits, most importantly we include LSS data with full k-dependence to explore the sensitivity of current data to the shape of the matter power spectrum. We find that LSS data prefer models with overall suppressed matter clustering due to dark matter - dark radiation interactions over ΛCDM at 3–4 σ. However recent weak lensing measurements of the power spectrum are not yet precise enough to clearly distinguish two limits of the model with different predicted shapes for the linear matter power spectrum. In two appendices we give a derivation of the coupled dark matter and dark radiation perturbation equations from the Boltzmann equation in order to clarify a confusion in the recent literature, and we derive analytic approximations to the solutions of the perturbation equations in the two physically interesting limits of all dark matter weakly interacting or a small fraction of dark matter strongly interacting.

Wrong sign Yukawa coupling of the 2HDM with a singlet scalar as dark matter confronted with dark matter and Higgs data

In the framework of type-II two-Higgs-doublet model with a scalar dark matter ($S$), we examine the wrong sign Yukawa coupling of the 125 GeV Higgs which is the only portal between the dark matter and SM sectors. After imposing the constraints from the Higgs searches at the LHC and dark matter experiments, we obtain some interesting observables: (i) The theory, oblique parameters, and the Higgs searches at the LHC can impose stringent constraints on $\tan\beta$ in the case of the wrong sign Yukawa coupling of the 125 GeV Higgs. For example, for $m_H=600$ GeV and 140 GeV $<m_A<200$ GeV, $\tan\beta$ is required to be in the range of 4.2 and 5.7. (ii) Due to the contribution of $SS\to AA$ annihilation channel to the relic density, the dark matter coupling with the 125 GeV Higgs can be sizably suppressed. However, the $SS\to AA$ channel can not solve the tension between the relic density and the signal data of 125 GeV Higgs for $m_S < 50$ GeV. (iii) The limits of XENON1T (2017) and PandaX-II (2017) exclude most of samples in the ranges of 65 GeV $<m_S<$ 78 GeV, $0.8<f^n/f^p<1$, and $y_d/y_u>-0.82$. (iv) The Fermi-LAT limits exclude most of samples in the range of 62.5 GeV $<m_S <65$ GeV, including the samples with $f^n/f^p\sim -0.7$.

Search for Axionlike Dark Matter through Nuclear Spin Precession in Electric and Magnetic Fields

We report on a search for ultra-low-mass axion-like dark matter by analysing the ratio of the spin-precession frequencies of stored ultracold neutrons and $^{199}$Hg atoms for an axion-induced oscillating electric dipole moment of the neutron and an axion-wind spin-precession effect. No signal consistent with dark matter is observed for the axion mass range $10^{-24}~\textrm{eV} \le m_a \le 10^{-17}~\textrm{eV}$. Our null result sets the first laboratory constraints on the coupling of axion dark matter to gluons, which improve on astrophysical limits by up to 3 orders of magnitude, and also improves on previous laboratory constraints on the axion coupling to nucleons by up to a factor of 40.

Search for domain wall dark matter with atomic clocks on board global positioning system satellites

Cosmological observations indicate that dark matter makes up 85% of all matter in the universe yet its microscopic composition remains a mystery. Dark matter could arise from ultralight quantum fields that form macroscopic objects. Here we use the global positioning system as a ~ 50,000 km aperture dark matter detector to search for such objects in the form of domain walls. Global positioning system navigation relies on precision timing signals furnished by atomic clocks. As the Earth moves through the galactic dark matter halo, interactions with domain walls could cause a sequence of atomic clock perturbations that propagate through the satellite constellation at galactic velocities ~ 300 km s−1. Mining 16 years of archival data, we find no evidence for domain walls at our current sensitivity level. This improves the limits on certain quadratic scalar couplings of domain wall dark matter to standard model particles by several orders of magnitude.

Extracting dark matter signatures from atomic clock stability measurements

We analyze possible effects of the dark matter environment on the atomic clock stability measurements. The dark matter is assumed to exist in a form of waves of ultralight scalar fields or in a form of topological defects (monopoles and strings). We identify dark matter signal signatures in clock Allan deviation plots that can be used to constrain the dark matter coupling to the Standard Model fields. The existing data on the Al+/Hg+ clock comparison are used to put new limits on the dilaton dark matter in the region of masses m > 10^{-15} eV. We also estimate the sensitivities of future atomic clock experiments in space, including the cesium microwave and strontium optical clocks aboard the International Space Station, as well as a potential nuclear clock. These experiments are expected to put new limits on the topological dark matter in the range of masses 10^{-10} eV < m < 10^{-6} eV.