Improved $${(g-2)_\mu }$$ measurements and wino/higgsino dark matter

The electroweak (EW) sector of the Minimal Supersymmetric Standard Model (MSSM) can account for a variety of experimental data. In particular it can explain the persistent $$3-4\,\sigma $$ 3 - 4 σ discrepancy between the experimental result for the anomalous magnetic moment of the muon, $$(g-2)_\mu $$ ( g - 2 ) μ , and its Standard Model (SM) prediction. The lightest supersymmetric particle (LSP), which we take as the lightest neutralino, $${\tilde{\chi }}_{1}^0$$ χ ~ 1 0 , can furthermore account for the observed Dark Matter (DM) content of the universe via coannihilation with the next-to-LSP (NLSP), while being in agreement with negative results from Direct Detection (DD) experiments. Concerning the unsuccessful searches for EW particles at the LHC, owing to relatively small production cross-sections a comparably light EW sector of the MSSM is in full agreement with the experimental data. The DM relic density can fully be explained by a mixed bino/wino LSP. Here we take the relic density as an upper bound, which opens up the possibility of wino and higgsino DM. We first analyze which mass ranges of neutralinos, charginos and scalar leptons are in agreement with all experimental data, including relevant LHC searches. We find roughly an upper limit of $$\sim 600 \,\, \mathrm {GeV}$$ ∼ 600 GeV for the LSP and NLSP masses. In a second step we assume that the new result of the Run 1 of the “MUON G-2” collaboration at Fermilab yields a precision comparable to the existing experimental result with the same central value. We analyze the potential impact of the combination of the Run 1 data with the existing $$(g-2)_\mu $$ ( g - 2 ) μ data on the allowed MSSM parameter space. We find that in this case the upper limits on the LSP and NLSP masses are substantially reduced by roughly $$100 \,\, \mathrm {GeV}$$ 100 GeV . We interpret these upper bounds in view of future HL-LHC EW searches as well as future high-energy $$e^+e^-$$ e + e - colliders, such as the ILC or CLIC.

Fermionic singlet dark matter in one-loop solutions to the $$R_K$$ anomaly: a systematic study

We study the dark matter phenomenology of Standard Model extensions addressing the reported anomaly in the $$R_K$$ R K observable at one-loop. The article covers the case of fermionic singlet DM coupling leptophilically, quarkphilically or amphiphilically to the SM. The setup utilizes a large coupling of the new particle content to the second lepton generation to explain the $$R_K$$ R K anomaly, which in return tends to diminish the dark matter relic density. Further, dark matter direct detection experiments provide stringent bounds even in cases where the dark matter candidate only contributes a small fraction of the observed dark matter energy density. In fact, direct detection rules out all considered models as an explanation for the $$R_K$$ R K anomaly in the case of Dirac dark matter. Conversely, for Majorana dark matter, the $$R_K$$ R K anomaly can be addressed in agreement with direct detection in coannihilation scenarios. For leptophilic dark matter this region only exists for $$M_\text {DM} \lesssim 1000 \, \mathrm {GeV}$$ M DM ≲ 1000 GeV and dark matter is underabundant. Quarkphilic and amphiphilic scenarios even provide narrow regions of parameter space where the observed relic density can be reproduced while offering an explanation to $$R_K$$ R K in agreement with direct detection experiments.

A Sub-GeV Low Mass Hidden Dark Sector of SU(2)H × U(1)X

We present a detailed study of the non-abelian vector dark matter candidate Wt with a MeV–GeV low mass range, accompanied by a dark photon A′ and a dark Z′ of similar masses, in the context of a gauged two-Higgs-doublet model with the hidden gauge group that has the same structure as the Standard Model electroweak gauge group. The stability of dark matter is protected by an accidental discrete Z2 symmetry (h-parity) which was usually imposed ad hoc by hand. We examine the model by taking into account various experimental constraints including dark photon searches at NA48, NA64, E141, ν-CAL, BaBar and LHCb experiments, electroweak precision data from LEP, relic density from Planck satellite, direct (indirect) detection of dark matter from CRESST-III, DarkSide-50, XENON1T (Fermi-LAT), and collider physics from the LHC. The theoretical requirements of bounded from below of the scalar potential and tree level perturbative unitarity of the scalar sector are also imposed. The viable parameter space of the model consistent with all the constraints is exhibited. While a dark Z′ can be the dominant contribution in the relic density due to resonant annihilation of dark matter, a dark photon is crucial to dark matter direct detection. We also demonstrate that the parameter space can be further probed by various sub-GeV direct dark matter experimental searches at CDEX, NEWS-G and SuperCDMS in the near future.

Dark matter, fine-tuning and (g-2)_{\mu} in the pMSSM

In this paper we perform for the first time an in-depth analysis of the spectra in the phenomenological supersymmetric Standard Model that simultaneously offer an explanation for the (g-2)_{\mu}(g−2)μ discrepancy \Delta a_{\mu}Δaμ, result in the right dark-matter relic density \Omega_{DM} h^2ΩDMh2 and are minimally fine-tuned. The resulting spectra may be obtained from [1]. To discuss the experimental exclusion potential for our models, we analyse the resulting LHC phenomenology as well as the sensitivity of dark-matter direct detection experiments to these spectra. We find that the latter type of experiments with sensitivity to the spin-dependent dark-matter–nucleon scattering cross section \sigma_{SD,p}σSD,p will probe all of our found solutions.

Two-loop radiative seesaw, muon g − 2, and τ-lepton-flavor violation with DM constraints

The quartic scalar coupling λ5 term, which violates the lepton-number by two units in the Ma-model, is phenomenologically small when the model is applied to the lepton-flavor violation (LFV) processes. In order to dynamically generate the λ5 parameter through quantum loop effects and retain the dark matter (DM) candidate, we extend the Ma-model by adding a Z2-odd vector-like lepton doublet and a Z2-even Majorana singlet. With the new couplings to the Higgs and gauge bosons, the observed DM relic density can be explained when the upper limits from the DM-nucleon scattering cross sections are satisfied. In addition to the neutrino data and LFV constraints, it is found that the DM relic density can significantly exclude the free parameter space. Nevertheless, the resulting muon g − 2 mediated by the inert charged-Higgs can fit the 4.2σ deviation between the experimental measurement and the SM result, and the branching ratio for τ → μγ can be as large as the current upper limit when the rare μ → (eγ, 3e) decays are suppressed. In addition, it is found that the resulting BR(τ → μρ) can reach the sensitivity of Belle II with an integrated luminosity of 50 ab−1.

A new way to test the WIMP dark matter models

In this paper, we investigate the possibility of testing the weakly interacting massive particle (WIMP) dark matter (DM) models by applying the simplest phenomenological model which introduces an interaction term between dark energy (DE) and WIMP DM, i.e., Q = 3γDMHρDM. In general, the coupling strength γDE is close to 0 as the interaction between DE and WIMP DM is very weak, thus the effect of γDE on the evolution of Y associated with DM energy density can be safely neglected. Meanwhile, our numerical calculation also indicates that xf ≈ 20 is associated with DM freeze-out temperature, which is the same as the vanishing interaction scenario. As for DM relic density, it will be magnified by $$ \frac{2-3{\upgamma}_{\mathrm{DM}}}{2}{\left[2\pi {g}_{\ast }{m}_{\mathrm{DM}}^3/\left(45{s}_0{x}_f^3\right)\right]}^{\gamma_{\mathrm{DM}}} $$ 2 − 3 γ DM 2 2 π g ∗ m DM 3 / 45 s 0 x f 3 γ DM times, which provides a new way to test WIMP DM models. As an example, we analyze the case in which WIMP DM is a scalar DM. (SGL+SNe+Hz) and (CMB+BAO+SNe) cosmological observations will give γDM = $$ {0.134}_{-0.069}^{+0.17} $$ 0.134 − 0.069 + 0.17 and γDM = −0.0008 ± 0.0016, respectively. After further considering the constraints from DM direct detection experiment, DM indirect detection experiment, and DM relic density, we find that the allowed parameter space of the scalar DM model will be completely excluded for the former cosmological observations, while it will increase for the latter ones. Those two cosmological observations lead to an almost paradoxical conclusion. Therefore, one could expect more stringent constraints on the WMIP DM models, with the accumulation of more accurate cosmological observations in the near future.