Detection Cross Section Research Articles

Limiting heavy-quark and gluonphilic real dark matter

We investigate the phenomenological viability of real spin half, zero, and one dark matter candidates, which interact predominantly with third-generation heavy quarks and gluons via the 28 gauge invariant higher-dimensional effective operators. The corresponding Wilson coefficients are constrained one at a time from the relic density ${\mathrm{\ensuremath{\Omega}}}^{\mathrm{DM}}{h}^{2}\ensuremath{\approx}0.1198$. Their contributions to the thermally-averaged annihilation cross sections are shown to be consistent with the FermiLAT and H.E.S.S. experiments' projected upper bound on the annihilation cross section in the $b\overline{b}$ mode. The tree-level gluonphilic and one-loop induced heavy-quarkphilic dark matter (DM) nucleon direct detection cross sections are analyzed. The nonobservation of any excess over expected background in the case of recoiled Xe nucleus events for spin-independent DM-nucleus scattering in XENON-1T sets the upper limits on the 18 Wilson coefficients. Our analysis validates the real DM candidates for the large range of accessible mass spectrum below 2 TeV for all but one interaction induced by the said operators.

Dark matter-induced multi-phase dynamical symmetry breaking

We consider the classically scale invariant Higgs-dilaton model of dynamical symmetry breaking extended with an extra scalar field that plays the role of dark matter. The Higgs boson is light near a critical boundary between different symmetry breaking phases, where quantum corrections beyond the usual Gildener-Weinberg approximation become relevant. This implies a tighter connection between dark matter and Higgs phenomenology. The model has only three free parameters, yet it allows for the observed relic abundance of dark matter while respecting all constraints. The direct detection cross section mediated by the Higgs boson is determined by the dark matter mass alone and is testable at future experiments.

Z-Portal Continuum Dark Matter.

We examine the possibility that dark matter (DM) consists of a gapped continuum, rather than ordinary particles. A weakly interacting continuum (WIC) model, coupled to the standard model via a Z portal, provides an explicit realization of this idea. The thermal DM relic density in this model is naturally consistent with observations, providing a continuum counterpart of the "WIMP miracle." Direct detection cross sections are strongly suppressed compared to ordinary Z-portal WIMP, thanks to a unique effect of the continuum kinematics. Continuum DM states decay throughout the history of the Universe, and observations of cosmic microwave background place constraints on potential late decays. Production of WICs at colliders can provide a striking cascade-decay signature. We show that a simple Z-portal WIC model provides a fully viable DM candidate consistent with all current experimental constraints.

Addendum to “Invisible Higgs decay width versus dark matter direct detection cross section in Higgs portal dark matter models”

This article is an addendum to Ref.~\cite{Baek:2014jga}. Here, we discuss the invisible Higgs decay width $\Gamma_{h}^{\rm inv}$ in the Higgs portal vector dark matter (VDM) model in the limit $m_V \rightarrow 0^+$. In the effective field theory (EFT) approach where the VDM mass is attributed to the St\"{u}ckelberg mechanism, $( \Gamma_{h}^{\rm inv} )_{\rm EFT}$ is divergent, which is unphysical and puzzling. On the other hand $( \Gamma_{h}^{\rm inv} )_{\rm UV}$ becomes finite in a UV completion, where the VDM mass is generated by the dark Higgs mechanism. Then we can take the limit $m_V \rightarrow 0^+$ by taking either {\it (i)} the dark gauge coupling $g_X \rightarrow 0^+$ with a fixed dark Higgs vacuum expectation value $v_\Phi$, or {\it (ii)} $v_\Phi \to 0^+$ with a fixed $g_X$. Such a difference in the behavior of $\Gamma_{h}^{\rm inv}$ in the massless VDM limit demonstrates another limitation of EFT for the Higgs portal VDM, and the importance of gauge-invariant and renormalizable models for the Higgs portal VDM.

Measurements of Total Sea Surface Mean Square Slope Field Based on SWIM Data

The total mean square slope (mss) of large-scale (in comparison with the scale of radar wavelengths) ocean waves can describe the roughness of the ocean surface. This important parameter has found many applications and can be determined by the dependence of large-scale mss on azimuthal angles. The Surface Waves Investigation and Monitoring instrument onboard the China France Oceanography Satellite (CFOSAT) can provide a two-dimensional (2D) normalized backscattering radar cross section (NRCS) for 2D global ocean-surface wave detection. In this paper, the 2D NRCS is used to calculate the total large-scale mss via two methods. The first method is constructed from regression, while the second scheme is derived from a three-solution method. Finally, the total large-scale mss are calculated using these methods, and the map of the distribution of the global total mss is presented for the first time. Our results show that the two sources of total large-scale mss obtained are consistent with each other. CFOSAT can provide a 2D total large-scale mss map and be used as a new data resource for global applications.

A complete effective field theory for dark matter

We present an effective field theory describing the relevant interactions of the Standard Model with an electrically neutral particle that can account for the dark matter in the Universe. The possible mediators of these interactions are assumed to be heavy. The dark matter candidates that we consider have spin 0, 1/2 or 1, belong to an electroweak multiplet with arbitrary isospin and hypercharge and their stability at cosmological scales is guaranteed by imposing a ℤ2 symmetry. We present the most general framework for describing the interaction of the dark matter with standard particles, and construct a general non-redundant basis of the gauge-invariant operators up to dimension six. The basis includes multiplets with non-vanishing hypercharge, which can also be viable DM candidates. We give two examples illustrating the phenomenological use of such a general effective framework. First, we consider the case of a scalar singlet, provide convenient semi-analytical expressions for the relevant dark matter observables, use present experimental data to set constraints on the Wilson coefficients of the operators, and show how the interplay of different operators can open new allowed windows in the parameter space of the model. Then we study the case of a lepton isodoublet, which involves coannihilation processes, and we discuss the impact of the operators on the particle mass splitting and direct detection cross sections. These examples highlight the importance of the contribution of the various non-renormalizable operators, which can even dominate over the gauge interactions in certain cases.

Exploring direct detection suppressed regions in a simple 2-scalar mediator model of scalar dark matter

We explore regions of parameter space that give rise to suppressed direct detection cross sections in a simple model of scalar dark matter with a scalar portal that mixes with the standard model Higgs. We found that even this simple model allows considerable room in the parameter space that has not been excluded by direct detection limits. A number of effects leading to this result have been previously noted. Our main new result explores interference effects between different contributions to DM annihilation when the DM mass is larger than the scalar portal mass. New annihilation channels open up and the parameters of the model need to compensate to give the correct DM relic abundance, resulting in smaller direct detection cross sections. We find that even in a very simple model of DM there are still sizeable regions of parameter space that are not ruled out by experiment.

Self-interacting neutrino portal dark matter

We present a realistic, simple and natural model of strongly-interacting dark matter based on the neutrino-portal paradigm. The strong interactions at small velocities are generated by the exchange of dark photons, and produce the observed core-like DM distribution in galactic centers; this effect could be spoiled by the formation of DM bound states (also due to dark-photon effects), which we avoid by requiring the DM candidates to be light, with masses below O(10 GeV). The mixing of the dark photon with the Z and ordinary photon is strongly suppressed by introducing a softly-broken discrete symmetry similar to charge conjugation, which also ensures that the dark photon life-time is short enough to avoid restrictions derived form big-bang nucleosynthesis and large-scale structure formation. Other constraints are accommodated without the need of fine tuning, in particular nucleon scattering occurs only at one loop, so direct detection cross sections are naturally suppressed. Neutrino masses are generated through the inverse see saw.

2HDM singlet portal to dark matter

Higgs portal models are the most minimal way to explain the relic abundance of the Universe. They add just a singlet that only couples to the Higgs through a single parameter that controls both the dark matter relic abundance and the direct detection cross-section. Unfortunately this scenario, either with scalar or fermionic dark matter, is almost ruled out by the latter. In this paper we analyze the Higgs-portal idea with fermionic dark matter in the context of a 2HDM. By disentangling the couplings responsible for the correct relic density from those that control the direct detection cross section we are able to open the parameter space and find wide regions consistent with both the observed relic density and all the current bounds.

Purely triplet seesaw and leptogenesis within cosmological bound, dark matter, and vacuum stability

In a novel standard model extension it has been suggested that, even in the absence of right-handed neutrinos and type-I seesaw, purely triplet leptogenesis leading to baryon asymmetry of the universe can be realized by two heavy Higgs triplets which also provide type-II seesaw ansatz for neutrino masses. In this work we discuss this model predictions for hierarchical neutrino masses in concordance with recently determined cosmological bounds and oscillation data including θ23 in the second octant and large Dirac CP phases. We find that for both normal and inverted orderings, the model fits the oscillation data with the sum of the three neutrino masses consistent with current cosmological bounds determined from Planck satellite data. In addition, using this model ansatz for CP-asymmetry and solutions of Boltzmann equations, we also show how successful predictions of baryon asymmetry emerges in the cases of both unflavoured and two-flavoured leptogeneses. With additional Z2 discrete symmetry, a minimal extension of this model is further shown to predict a scalar singlet WIMP dark matter in agreement with direct and indirect observations which also resolves the issue of vacuum instability persisting in the original model. Although the combined constraints due to relic density and direct detection cross section allow this scalar singlet dark matter mass to be mξ=750 GeV, the additional vacuum stability constraint pushes this limiting value to mξ=1.3 TeV which is verifiable by ongoing experiments. We also discuss constraint on the model parameters for the radiative stability of the standard Higgs mass.

Dark Matter in scalar Sp( mathcal{N} ) gauge dynamics

We consider a model with Sp dark gauge group and a scalar field in the fundamental representation, which leads to two co-stable DM candidates at the perturbative level thanks to a global U(1) accidental symmetry. After gauge confinement at low energy scale, only one of the two candidates is still stable. We compute the DM relic abundance by solving the Boltzmann equations numerically. The presence of light dark glueballs gives extra cosmological effects and can affect Higgs physics. We study the DM phenomenology, providing the predictions for direct and indirect detection (including the Sommerfeld enhancement). We show that the model predicts a slightly suppressed indirect detection cross section in comparison to the usual WIMPs paradigm.

Pseudo-Nambu-Goldstone dark matter from gauged U(1)B\u2212L symmetry

A pseudo-Nambu-Goldstone boson (pNGB) is an attractive candidate for dark matter since the current severe limits of dark matter direct detection experiments are naturally evaded by its nature. We construct a model with pNGB dark matter based on a gauged U (1)B−L symmetry, where no adhoc global symmetry is assumed. The model keeps natural suppression mechanism for the dark matter direct detection cross section. On the other hand, the pNGB can decay through the new high scale suppressed operators. We show that the pNGB has long enough lifetime to be a dark matter in the wide range of the parameter space of the model. The thermal relic abundance of pNGB dark matter can be fit with the observed value against the constraints on the dark matter decays from the cosmic-ray observations.

Generalized blind spots for dark matter direct detection in the 2HDM

In this paper we study the presence of generalized blind spots, i.e. regions of the parameter space where the spin-independent cross section for dark matter direct detection is suppressed, in the context of a generic 2HDM and a minimal fermionic Higgs-portal dark sector. To this end, we derive analytical expressions for the couplings of the dark matter to the light and heavy Higgses, and thus for the blind spot solutions. Unlike the case of a standard Higgs sector, blind spots can occur even without a cancellation between different contributions, while keeping unsuppressed and efficient the annihilation processes in the early Universe involving Higgs states. As a consequence, the allowed parameter space is dramatically enhanced.

Exploring Dark Matter, Neutrino mass and flavour anomalies in L μ – L τ model

We investigate Majorana dark matter in a new variant of U(1) Lμ – Lτ gauge extension of Standard Model, containing three additional neutral fermions Ne, Nμ, Nτ , along with a (, 1, 1/3) scalar Leptoquark (SLQ) and an inert doublet, to study the phenomenology of dark matter, neutrino mass generation and flavour anomalies on a single platform. The lightest mass eigenstate of the Nμ, Nτ neutral fermions plays the role of dark matter. We compute the WIMP-nucleon cross section in leptoquark portal and the relic density mediated by inert doublet components, leptoquark and the new Z′ boson. We constrain the parameter space consistent with Planck limit on relic density, PIC0-60 and LUX bounds on spin-dependent direct detection cross section. We also discuss about the neutrino mass generation at one-loop level and the viable parameter region to explain current neutrino oscillation data. The Z′ gauge boson of extended U(1) symmetry and the SLQ play an important role in settling the known issues of flavor sector.

MicroMegas-based detectors for time-of-flight measurements of neutron-induced reactions

MicroMegas detectors are versatile gaseous detectors which are used for ionizing particle detection. A MicroMegas detector consists of two adjacent gas-filled volumes. One volume acts as a drift region with an electric field operating in the ionization chamber regime, the second volume is the amplification region acting as a parallel-plate avalanche counter. The use of the microbulk technique allows the production of thin, radiation resistant, and low-mass detector with a highly variable gain. Such MicroMegas detectors have been developed and used in combination with neutron time-of-flight measurements for in-beam neutron-flux monitoring, fission and light-charged particle reaction cross section measurements, and for neutron-beam imaging. An overview of MicroMegas detectors for neutron detection and neutron reaction cross section measurements and related results and developments will be presented.

Electroweak corrections to dark matter direct detection in a vector dark matter model

Although many astrophysical and cosmological observations point towards the existence of Dark Matter (DM), the nature of the DM particle has not been clarified to date. In this paper, we investigate a minimal model with a vector DM (VDM) candidate. Within this model, we compute the cross section for the scattering of the VDM particle with a nucleon. We provide the next-to-leading order (NLO) cross section for the direct detection of the DM particle. Subsequently, we study the phenomenological implications of the NLO corrections, in particular with respect to the sensitivity of the direct detection DM experi- ments. We further investigate more theoretical questions such as the gauge dependence of the results and the remaining theoretical uncertainties due to the applied approximations.

Testing dark matter with Cherenkov light \u2014 prospects of H.E.S.S. and CTA for exploring minimal supersymmetry

We provide an updated and improved study of the prospects of the H.E.S.S. and Cherenkov Telescope Array (CTA) experiments in testing neutralino dark matter in the Minimal Supersymmetric Standard Model with nine free parameters (p9MSSM). We include all relevant experimental constraints and theoretical developments, in particular a calculation of the Sommerfeld enhancement for both present-day annihilations and the relic abundance. We perform a state-of-the-art analysis of the CTA sensitivity with a log- likelihood test ratio statistics and apply it to a numerical scan of the p9MSSM parameter space focusing on a TeV scale dark matter. We find that, assuming Einasto profile of dark matter halo in the Milky Way, H.E.S.S. has already been able to nearly reach the so-called thermal WIMP value, while CTA will go below it by providing a further improvement of at least an order of magnitude. Both H.E.S.S. and CTA are sensitive to several cases for which direct detection cross section will be below the so-called neutrino floor, with H.E.S.S. being sensitive to most of the wino region, while CTA also covering a large fraction of the ∼1 TeV higgsino region. We show that CTA sensitivity will be further improved in the monochromatic photon search mode for both single-component and underabundant dark matter.

Return of the WIMP: Missing energy signals and the Galactic Center excess

In a recent work, we emphasized that an excess in tri-lepton events plus missing energy observed by the ATLAS experiment at the LHC could be interpreted as a signal of low energy supersymmetry. In such a scenario the lightest neutralino mass is approximately $m_\chi \simeq 60$ GeV and the direct Dark Matter detection cross section is naturally below the current bound. In this work we present simple extensions of this scenario that lead to an explanation of the gamma ray excess at the center of the galaxy observed by Fermi-LAT, as well as the anti-proton excess observed by AMS-02. These extensions include the addition of a small CP violating phase in the neutralino sector or the addition of a light CP-odd Higgs scalar. Our study is of special relevance in view of a recent analysis that casts doubt on the previously accepted preference for mili-second pulsars as the origin of the galactic center excess.

K ‐coverage based receiver placement optimisation in passive radar network

In passive radar network (PRN), the receiver placement optimisation which has the ability to improve the coverage performance attracts much attention recently. In this study, the K-coverage performance is considered since the pre-condition of deghosting in a radar network is that the target has to be covered by K K ≥ 3 bistatic pairs. Thus, a K-coverage-based receiver placement optimisation is formulated, in which a weighted M-centre model and the required radar cross section (RCS) for target detection are involved. Moreover, in order to solve this high dimensional optimisation problem, an iterative method which is based on K-order Voronoi algorithm and neighbourood search is proposed. Finally, the proposed method shows its effectiveness in solving the K-coverage optimisation problem of PRN via simulations. Specially, the probability of K-coverage is up to 99.8% with the optimal placement.

Scalar electroweak multiplet dark matter

We revisit the theory and phenomenology of scalar electroweak multiplet thermal dark matter. We derive the most general, renormalizable scalar potential, assuming the presence of the Standard Model Higgs doublet, H, and an electroweak multiplet Φ of arbitrary SU(2)L rank and hypercharge, Y. We show that, in general, the Φ-H Higgs portal interactions depend on three, rather than two independent couplings as has been previously considered in the literature. For the phenomenologically viable case of Y = 0 multiplets, we focus on the septuplet and quintuplet cases, and consider the interplay of relic density and spin-independent direct detection cross section. We show that both the relic density and direct detection cross sections depend on a single linear combination of Higgs portal couplings, λeff. For λeff ∼ mathcal{O} (1), present direct detection exclusion limits imply that the neutral component of a scalar electroweak multiplet would comprise a subdominant fraction of the observed DM relic density.