Dark Matter Relic Density Research Articles

Constraints on the epoch of dark matter formation from Milky Way satellites

A small fraction of thermalized dark radiation that transitions into cold dark matter (CDM) between big bang nucleosynthesis and matter-radiation equality can account for the entire dark matter relic density. Because of its transition from dark radiation, "late-forming dark matter" (LFDM) suppresses the growth of linear matter perturbations and imprints the oscillatory signatures of dark radiation perturbations on small scales. The cutoff scale in the linear matter power spectrum is set by the redshift $z_T$ of the phase transition; tracers of small-scale structure can therefore be used to infer the LFDM formation epoch. Here, we use a forward model of the Milky Way (MW) satellite galaxy population to address the question: How late can dark matter form? For dark radiation with strong self-interactions, which arises in theories of neutrinolike LFDM, we report $z_{T}>5.5\times 10^6$ at $95\%$ confidence based on the abundance of known MW satellite galaxies. This limit rigorously accounts for observational incompleteness corrections, marginalizes over uncertainties in the connection between dwarf galaxies and dark matter halos, and improves upon galaxy clustering and Lyman-$\alpha$ forest constraints by nearly an order of magnitude. We show that this limit can also be interpreted as a lower bound on $z_T$ for LFDM that free-streams prior to its phase transition, although dedicated simulations will be needed to analyze this case in detail. Thus, dark matter created by a transition from dark radiation must form no later than one week after the big bang.

An information theoretic exploration of constrained MSSM

We discuss information theory as a tool to investigate constrained minimal supersymmetric Standard Model (CMSSM) in the light of observation of Higgs boson at the Large Hadron Collider. The entropy of the Higgs boson using its various detection modes has been constructed as a measure of the information and has been utilized to explore a wide range of CMSSM parameter space after including various experimental constraints from the LEP data, B-physics, electroweak precision observables and relic density of dark matter. According to our study while the lightest neutralino is preferred to have a mass around 1.92 TeV, the gluino mass is estimated to be around 7.44 TeV. The values of CMSSM parameters m0, m1/2, A0 and tan⁡β correspond to the most preferred scenario are found to be about 6 TeV, 3.6 TeV, −6.9 TeV and 36.8 respectively.

Higgsino asymmetry and direct-detection constraints of light dark matter in the NMSSM with non-universal Higgs masses * *Supported by the National Natural Science Foundation of China (11605123)

In this study, we analyze the direct-detection constraints of light dark matter in the next-to minimal supersymmetric standard model (NMSSM) with non-universal Higgs masses (NUHM); we specially focus on the correlation between higgsino asymmetry and spin-dependent (SD) cross section. We draw the following conclusions. (i) The SD cross section is proportional to the square of higgsino asymmetry in dark matter in the NMSSM-NUHM, and hence, it is small for highly singlino-dominated dark matter. (ii) The higgsino-mass parameter is smaller than approximately in the NMSSM-NUHM due to the current muon g-2 constraint, but our scenario with light dark matter can still be alive under current constraints including the direct detection of dark matter in the spin-dependent channel. (iii) With a sizeable higgsino component in the light dark matter, the higgsino asymmetry and SD cross section can also be sizeable, but dark matter relic density is always small; thus, it can escape the direct detections. (iv) Light dark matter in the - and Z-funnel annihilation channels with sufficient relic density can be covered by future LUX-ZEPLIN (LZ) 7-ton in SD detections. (v) The spin-independent (SI) cross section is dominated by - and -exchanging channels, which can even cancel each other in some samples, leaving an SI cross section smaller by a few orders of magnitude than that of one individual channel.

Light dark matter from dark sector decay

We study the possibility that light dark matter can be produced with right relic density by the decay of other dark sector particles. We study this possibility in a model with right-handed neutrinos, a dark sector singlet scalar and a dark sector singlet fermion. The decay of the heavier dark sector singlet scalar gives rise to the lighter dark sector singlet fermion which serves as the dark matter candidate. We show that the right dark matter relic density can be produced by the decay of the dark sector singlet scalar. We find that the mass of the dark sector singlet fermion can be GeV scale or MeV scale and the interaction of the dark sector singlet fermion is very weak. The dark sector singlet scalar can have a mass of GeV-TeV scale and can have weak scale interactions with the Standard Model (SM) particles. So, in this scenario, dark matter has an interaction with the SM much weaker than the weak interaction, but the dark sector still has weak scale interaction with the SM.

Dark Matter Constraints and the Neutralino Sector of the scNMSSM

The neutralino sector of the semi-constrained next-to-minimal supersymmetric standard model is explored under recent experimental constraints, with special attention to dark matter (DM) limits. The effects of the upper and lower bounds of dark matter relic density and recent direct detection constraints on spin-independent and -dependent cross-sections are thoroughly analyzed. Particularly, we show which regions of the parameter space are ruled out due to the different dark matter constraints and the corresponding model-specific parameters: λ,κ,Aλ, and Aκ. We analyze all annihilation and co-annihilation processes (with heavier neutralinos and charginos) that contribute to the dark matter relic density. The mass components of the dark matter candidate, the lightest neutralino χ˜10, are studied, and the decays of heavy neutralinos and charginos, especially χ˜20 and χ˜1+, into the lightest neutralino are examined. We impose semi-universal boundary conditions at the Grand Unified Theory scale, and require a moderate range of tanβ≲10. We find that the allowed parameter space is associated with a heavy mass spectrum in general and that the lightest neutralino is mostly Higgsino with a mass range that resides mostly between 1000 and 1500 GeV. However, smaller mass values can be achieved if the DM candidate is bino-like or singlino-like.

Current bounds and future prospects of light neutralino dark matter in the NMSSM

Unlike its minimal counterpart, the Next to Minimal supersymmetric Standard Model (NMSSM) allows the possibility that the lightest neutralino could have a mass as small as $\sim 1 {\rm GeV}$ while still providing a significant component of relic dark matter (DM). Such a neutralino can provide an invisible decay mode to the Higgs as well. Further, the observed SM-like Higgs boson ($H_{125}$) could also have an invisible branching fraction as high as $\sim 19\%$. Led by these facts, we first delineate the region of parameter space of the NMSSM with a light neutralino ($M_{{\tilde{\chi}}_{1}^{0}} < 62.5 {\rm GeV}$) that yields a thermal neutralino relic density smaller than the measured relic density of cold dark matter, and is also compatible with constraints from collider searches, searches for dark matter, and from flavor physics. We then examine the prospects for probing the NMSSM with a light neutralino via direct DM detection searches, via invisible Higgs boson width experiments at future $e^+e^-$ colliders, via searches for a light singlet Higgs boson in $2b2\mu$, $2b2\tau$ and $2\mu2\tau$ channels and via pair production of winos or doublet higgsinos at the high luminosity LHC and its proposed energy upgrade. For this last-mentioned electroweakino search, we perform a detailed analysis to map out the projected reach in the $3l+{\rm E{\!\!\!/}_T}$ channel, assuming that chargino decays to $W {\tilde{\chi}}_{1}^{0}$ and the neutralino(s) decay to $Z$ or $H_{125}$ + ${\tilde{\chi}}_{1}^{0}$. We find that the HL-LHC can discover SUSY in just part of the parameter space in each of these channels, which together can probe almost the entire parameter space. The HE-LHC probes essentially the entire region with higgsinos (winos) lighter than 1 TeV (2 TeV) independently of how the neutralinos decay, and leads to significantly larger signal rates.

Probing photophobic axion and relaxion dark matter

We investigate the interplay between early universe cosmology and dark matter direct detection, considering axion models with naturally suppressed couplings to photons. In the context of the cosmological relaxation of the electroweak scale, we focus on a scenario of \emph{Relaxion Dark Matter}, in which the relaxion field constitutes all the observed dark matter relic density and its allowed mass range is fixed to a few $\mathrm{keV}$ by construction. In particular, we show that a relaxion particle with mass $m_\phi= 3.0 \,\mathrm{keV}$ which couples to electrons with $g_{\phi, e}= 6.8 \times 10^{-14}$ is consistent with the XENON1T excess, while accounting for the observed dark matter and satisfying astro/cosmo probes. This scenario uses the electroweak scale as the link connecting the relaxion production at early times with the dark matter absorption rate in direct detection.

Neutrino floor in leptophilic U(1) models: Modification in U(1)Lμ−Lτ

In this work, we investigate the beyond standard model (BSM) impact of leptophilic U(1) models, namely $ U(1)_{L_\mu-L_e}$, $U(1)_{L_e-L_\tau}$ and $U(1)_{L_\mu-L_\tau}$ on coherent elastic neutrino-nucleus scattering (CE$\nu$NS) and hence its effect on dark matter (DM) direct detection experiments. Imposing the latest relevant experimental constraints on these models, we obtain $\mathcal{O}(50\%)$ enhancement for case of $U(1)_{L_\mu-L_\tau}$ in a region $m_Z' \approx 20~$MeV. Subsequently, we observe that the enhancement seen in CE$\nu$NS is roughly getting translated to enhancement by a factor of 2.7 (for Germanium based detectors) and 1.8 (for Xenon based detectors) in the neutrino scattering event rate which eventually enhances the neutrino floor by same amount. This enhancement is more prominent in the region with DM masses less than 10 GeV. The model parameter space that leads to this enhancement, can simultaneously explain both anomalous magnetic moment of muon ($(g-2)_{\mu}$) and observed DM relic density, in a modified scenario. Enhancement of neutrino floor requires increased number of DM-nucleon scattering events in the future DM direct detection experiments, to establish themselves to be DM signal events. In absence of any DM signal, those experiments can directly be used to measure the neutrino rate, quantifying the BSM effects.

Light dark matter in a minimal extension with two additional real singlets

The direct searches for heavy scalar dark matter with a mass of order 100 GeV are much more sensitive than for light dark matter of order 1 GeV. The question arises whether dark matter could be light and has escaped detection so far. We study a simple extension of the Standard Model with two additional real singlets. We show that this simple extension may provide the observed relic dark matter density, does neither disturb big-bang nucleosynthesis nor the cosmic microwave background radiation observations and fulfills the conditions of clumping behavior for different sizes of galaxies. The potential of one Standard Model-like Higgs-boson doublet and the two singlets gives rise to a changed Higgs phenomenology, in particular, an enhanced invisible Higgs-boson decay rate is expected, detectable by missing transversal momentum searches at the ATLAS and CMS experiments at CERN.

Electroweak phase transition confronted with dark matter detection constraints

We study the type-II first-order electroweak phase transition and dark matter (DM) phenomenology in both real and complex singlet extensions of SM . In the real singlet extension with a ℤ2 symmetry, we show that the parameter regions favored by the phase transition suffer from strong constraints from DM direct detection so that only a negligible fraction (fX∼ 10−4−10−5) of DM composed of the real singlet scalar can survive the LUX and XENON1T constraints. In the complex singlet S case, we impose a CP symmetry S→ S* to the scalar potential. The real component of S can mix with SM Higgs boson while the imaginary component becomes a DM candidate due to the protection of the CP symmetry. By taking into account the current experimental constraints of invisible Higgs decays, Higgs signal strength measurements, and dark matter detections, we find that there exists a large parameter space for the type-II electroweak phase transition to occur while explaining all of the dark matter relic density. We identify a subset of parameter space that is promising for future experiments, including the di-Higgs and Higgs signal strength measurements at the HL-LHC and the dark matter direct detection in the XENONnT project.

Collider probes of real triplet scalar dark matter

We study discovery prospects for a real triplet extension of the Standard Model scalar sector at the Large Hadron Collider (LHC) and a possible future 100 TeV pp collider. We focus on the scenario in which the neutral triplet scalar is stable and contributes to the dark matter relic density. When produced in pp collisions, the charged triplet scalar decays to the neutral component plus a soft pion or soft lepton pair, yielding a disappearing charged track in the detector. We recast current 13 TeV LHC searches for disappearing tracks, and find that the LHC presently excludes a real triplet scalar lighter than 248 (275) GeV, for a mass splitting of 172 (160) MeV with ℒ = 36 fb−1. The reach can extend to 497 (520) GeV with the collection of 3000 fb−1. We extrapolate the 13 TeV analysis to a prospective 100 TeV pp collider, and find that a ∼ 3 TeV triplet scalar could be discoverable with ℒ = 30 ab−1, depending on the degree to which pile up effects are under control. We also investigate the dark matter candidate in our model and corresponding present and prospective constraints from dark matter direct detection. We find that currently XENON1T can exclude a real triplet dark matter lighter than ∼ 3 TeV for a Higgs portal coupling of order one or larger, and the future XENON20T will cover almost the entire dark matter viable parameter space except for vanishingly small portal coupling.

Dark initial state radiation and the kinetic mixing portal

Data from Planck measurements of the cosmic microwave background (CMB) place important constraints on models with light dark matter (DM) and light mediators especially when both lie in the mass range below ∼ 1 GeV. In models involving kinetic mixing where the dark photon acts as the mediator, these constraints are easily satisfied and the appropriate DM relic density achievable if the DM is, e.g., a complex scalar, where p-wave annihilation occurs, or is the lighter component of a split pseudo-Dirac state where co-annihilation dominates. In both of these cases, although higher order in the dark gauge coupling, gD, the corresponding annihilation processes including dark photon initial state radiation (ISR) will be dominantly s-wave with essentially temperature independent cross sections. The rates for these dark ISR associated processes, though not yielding cross sections large enough to contribute to the relic density, can still run into possible conflicts with the bounds arising from the CMB. In this paper we perform a preliminary study of the present and potential future constraints that the CMB imposes on the parameter spaces for both of these scenarios due to the existence of this dark ISR. Further analyses of the effects of dark ISR in DM annihilation is clearly warranted.

Opening the 1 Hz axion window

An axion-like particle (ALP) with mass mϕ ∼ 10−15 eV oscillates with frequency ∼1 Hz. This mass scale lies in an open window of astrophysical constraints, and appears naturally as a consequence of grand unification (GUT) in string/M-theory. However, with a GUT-scale decay constant such an ALP overcloses the Universe, and cannot solve the strong CP problem. In this paper, we present a two axion model in which the 1 Hz ALP constitutes the entirety of the dark matter (DM) while the QCD axion solves the strong CP problem but contributes negligibly to the DM relic density. The mechanism to achieve the correct relic densities relies on low-scale inflation (mϕ ≲ Hinf ≲ 1 MeV), and we present explicit realisations of such a model. The scale in the axion potential leading to the 1 Hz axion generates a value for the strong CP phase which oscillates around {overline{theta}}_{mathrm{QCD}}sim {10}^{-12} , within reach of the proton storage ring electric dipole moment experiment. The 1 Hz axion is also in reach of near future laboratory and astrophysical searches.

Sommerfeld enhancements for asymmetric dark matter

We extend the analysis of asymmetric Dark Matter relic density with the Sommerfeld enhancement to the case where the mediator is massive. In asymmetric Dark Matter models, asymmetric Dark Matter is assumed to couple to the light scalar or vector boson. Asymmetric Dark Matter annihilation cross section is enhanced by the Sommerfeld effect which exists due to the distortion of the wavefunction of asymmetric Dark Matter particle and anti–particle by long–range interactions. The impacts of the Sommerfeld enhancement on the relic densities of asymmetric Dark Matter particle and anti–particle are discussed. The effect of kinetic decoupling on the relic density is also probed when the annihilation cross section is boosted by the Sommerfeld enhancement. Finally, the constraints on the parameter space are given using the observational data of the relic density of Dark Matter.

Baryon and lepton number violation from gravitational waves

We describe a unique gravitational wave signature for a class of models with a vast hierarchy between the symmetry breaking scales. The unusual shape of the signal is a result of the overlapping contributions to the stochastic gravitational wave background from cosmic strings produced at a high scale and a cosmological phase transition at a low scale. We apply this idea to a simple model with gauged baryon and lepton number, in which the high-scale breaking of lepton number is motivated by the seesaw mechanism for the neutrinos, whereas the low scale of baryon number breaking is required by the observed dark matter relic density. The novel signature can be searched for in upcoming gravitational wave experiments.

Dark matter interactions in an S4×Z5 flavor symmetry framework

The interactions of dark matter (DM) with the visible sector are often phenomenologically described in the framework of simplified models where the couplings of quarks to the new particles are generally assumed to be universal or have a simple structure motivated by observational benchmarks. They should, however, a priori be treated as free parameters. In this work we discuss one particular realization of the structure of DM couplings based on an $S_4 \times Z_5$ flavor symmetry, which has been shown to account reasonably well for fermion masses and mixing, and compare their effect on observational signals to universal as well as Yukawa-like couplings, which are motivated by minimal flavor violation. We will also comment on how these structures could be constrained in UV complete theories of DM and how DM observables, such as, e.g., relic density and direct detection, can potentially be used as a smoking gun for the underlying flavor symmetries.

Right-handed neutrino dark matter, neutrino masses, and non-standard cosmology in a 2HDM

We explore the dark matter phenomenology of a weak-scale right-handed neutrino in the context of a Two Higgs Doublet Model. The expected signal at direct detection experiments is different from the usual spin-independent and spin-dependent classification since the scattering with quarks depends on the dark matter spin. The dark matter relic density is set by thermal freeze-out and in the presence of non-standard cosmology, where an Abelian gauge symmetry is key for the dark matter production mechanism. We show that such symmetry allows us to simultaneously address neutrino masses and the flavor problem present in general Two Higgs Doublet Model constructions. Lastly, we outline the region of parameter space that obeys collider, perturbative unitarity and direct detection constraints.

Observable signatures of scotogenic Dirac model

In this work, we make a detailed discussion on the phenomenology of the scotogenic Dirac model, which could accommodate the Dirac neutrino mass and dark matter. We have studied the lepton-flavor-violating (LFV) processes in this model, which are mediated by the charged scalar ϕ± and heavy Dirac fermions Ni. The experimental bounds, especially given by decays μ → eγ and μ → 3e, have put severe constraints on the Yukawa couplings yΦ and masses mN1, mϕ. We select the heavy Dirac fermion N1 as dark matter candidate and find the correct relic density will be reached basically by annihilating through another Yukawa coupling yχ. After satisfying LFV and dark matter relic density constraints, we consider the indirect detections of dark matter annihilating into leptons. But the constraints are relatively loose, only the τ+τ− channel can impose a mild excluding capability. Then we make a detailed discussion on the dark matter direct detections. Although two Yukawa couplings can both contribute to the direct detection processes, more attention has been paid on the yΦ-related processes as the yχ-related process is bounded loosely. The current and future direct detection experiments have been used to set constraints on the Yukawa couplings and masses. The current direct detections bounds are relatively loose and can barely exclude more parameter region beyond the LFV. For the future direct detection experiments, the excluding capacities can be improved due to larger exposures. The detecting capabilities in the large mass region have not been weakened as the existence of mass enhancement from the magnetic dipole operator {mathcal{O}}_{mathrm{mag}.} . At last, we have briefly discussed the collider signal searching in this model, the most promising signature is pair produced ϕ+ϕ− and decay into the signal of ℓ+ℓ− + ɆT. The exclusion limits from collider on mN1 and mϕ have provided a complementary detecting capability compared to the LFV and dark matter detections.

Status of low mass LSP in SUSY

In this article we review the case for a light ($< m_{h_{125}}/2$) neutralino and sneutrino being a viable Dark Matter (DM) candidate in Supersymmetry(SUSY). To that end we recapitulate, very briefly, three issues related to the DM which impact the discussions : calculation of DM relic density, detection of the DM in Direct and Indirect experiments and creation /detection at the Colliders. In case of SUSY, the results from Higgs and SUSY searches at the colliders also have implications for the DM mass and couplings. In view of the constraints coming from all these sources, the possibility of a light neutralino is all but ruled out for the constrained MSSM : cMSSM. The pMSSM, where the gaugino masses are not related at high scale, is also quite constrained and under tension in case of thermal DM and will be put to very stern test in the near future in Direct Detection (DD) experiments as well as by the LHC analyses. However in the pMSSM with modified cosmology and hence non-thermal DM or in the NMSSM, a light neutralino is much more easily accommodated. A light RH sneutrino is also still a viable DM candidate although it requires extending the MSSM with additional singlet neutrino superfields. All of these possibilities can be indeed tested jointly in the upcoming SUSY-electroweakino and Higgs searches at the HL/HE luminosity LHC, the upcoming experiments for the Direct Detection (DD) and indirect detection for the DM as well as the high precision electron-positron colliders under planning.

Dirac dark matter in a radiative neutrino model

We propose a simple radiative neutrino mass scenario with a Dirac dark matter candidate, which is minimally realized by a Z3 symmetry. We introduce two Dirac neutrinos and two inert doublets. We demonstrate that the model has a large allowed region that satisfies the constraints from neutrino oscillation data, lepton flavor violations, direct/indirect detection of dark matter and dark matter relic density. We also propose an efficient parameterization of the neutrino Yukawa couplings, which reproduces a desired active neutrino mass matrix.