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Register a new userProbing the explanation of the muon (g-2) anomaly and thermal light dark matter with the semi-visible dark photon channel
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We report the results of a search for a new vector boson ($A$) decaying into two dark matter particles $chi_1 chi_2$ of different mass. The heavier $chi_2$ particle subsequently decays to $chi_1$ and $A to e^- e^+$. For a sufficiently large mass splitting, this model can explain in terms of new physics the recently confirmed discrepancy observed in the muon anomalous magnetic moment at Fermilab. Remarkably, it also predicts the observed yield of thermal dark matter relic abundance. A detailed Monte-Carlo simulation was used to determine the signal yield and detection efficiency for this channel in the NA64 setup. The results were obtained re-analyzing the previous NA64 searches for an invisible decay $Ato chi overline{chi}$ and axion-like or pseudo-scalar particles $a to gamma gamma$. With this method, we exclude a significant portion of the parameter space justifying the muon g-2 anomaly and being compatible with the observed dark matter relic density for $A$ masses from 2$m_e$ up to 390 MeV and mixing parameter $epsilon$ between $3times10^{-5}$ and $2times10^{-2}$.
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We explore the ability of current and future dark matter and collider experiments in probing anomalous magnetic moment of the muon, $(g-2)_mu$, within the Minimal Supersymmetric Standard Model (MSSM). We find that the latest PandaX-II/LUX-2016 data gives a strong constraint on parameter space that accommodates the $(g-2)_{mu}$ within $2sigma$ range, which will be further excluded by the upcoming XENON-1T (2017) experiment. We also find that a 100 TeV $pp$ collider can cover most of our surviving samples that satisfy DM relic density within $3sigma$ range through $Z$ or $h$ resonant effect by searching for trilepton events from $tilde{chi}^0_2tilde{chi}^+_1$ associated production. While the samples that are beyond future sensitivity of trilepton search at a 100 TeV $pp$ collider and the DM direct detections are either higgsino/wino-like LSPs or bino-like LSPs co-annihilating with sleptons. Such compressed regions may be covered by the monojet(-like) searches at a 100 TeV $pp$ collider.
We construct models with minimal field content that can simultaneously explain the muon g-2 anomaly and give the correct dark matter relic abundance. These models fall into two general classes, whether or not the new fields couple to the Higgs. For the general structure of models without new Higgs couplings, we provide analytical expressions that only depend on the $SU(2)_L$ representation. These results allow to demonstrate that only few models in this class can simultaneously explain $(g-2)_mu$ and account for the relic abundance. The experimental constraints and perturbativity considerations exclude all such models, apart from a few fine-tuned regions in the parameter space, with new states in the few 100 GeV range. In the models with new Higgs couplings, the new states can be parametrically heavier by a factor $sqrt{1/y_mu}$, with $y_mu$ the muon Yukawa coupling, resulting in masses for the new states in the TeV regime. At present these models are not well constrained experimentally, which we illustrate on two representative examples.
We propose simple models with a flavor-dependent global $U(1)_ell$ and a discrete $mathbb{Z}_2$ symmetries to explain the anomalies in the measured anomalous magnetic dipole moments of muon and electron, $(g-2)_{mu,e}$, while simultaneously accommodating a dark matter candidate. These new symmetries are introduced not only to avoid the dangerous lepton flavor-violating decays of charged leptons, but also to ensure the stability of the dark matter. Our models can realize the opposite-sign contributions to the muon and electron $g-2$ via one-loop diagrams involving new vector-like leptons. Under the vacuum stability and perturbative unitarity bounds as well as the constraints from the dark matter direct searches and related LHC data, we find suitable parameter space to simultaneously explain $(g-2)_{mu,e}$ and the relic density. In this parameter space, the coupling of the Higgs boson with muons can be enhanced by up to $sim 38%$ from its Standard Model value, which can be tested in future collider experiments.
In this paper, we summarize phenomenology in lepton portal dark matter (DM) models, where DM couples to leptons and extra leptons/sleptons. There are several possible setups: complex/real scalar DM and Dirac/Majorana fermion DM. In addition, there are choices for the lepton chirality that couples to DM. We discuss the prediction of each model and compare it with the latest experimental constraints from the DM, the LHC, and the flavor experiments. We also propose a simple setup to achieve the discrepancy in the anomalous magnetic moment of muon.
The longstanding $4.2 , sigma$ muon $g-2$ anomaly may be the result of a new particle species which could also couple to dark matter and mediate its annihilations in the early universe. In models where both muons and dark matter carry equal charges under a $U(1)_{L_mu-L_tau}$ gauge symmetry, the corresponding $Z^prime$ can both resolve the observed $g-2$ anomaly and yield an acceptable dark matter relic abundance, relying on annihilations which take place through the $Z^prime$ resonance. Once the value of $(g-2)_{mu}$ and the dark matter abundance are each fixed, there is very little remaining freedom in this model, making it highly predictive. We provide a comprehensive analysis of this scenario, identifying a viable range of dark matter masses between approximately 10 and 100 MeV, which falls entirely within the projected sensitivity of several accelerator-based experiments, including NA62, NA64$mu$, $M^3$, and DUNE. Furthermore, portions of this mass range predict contributions to $Delta N_{rm eff}$ which could ameliorate the tension between early and late time measurements of the Hubble constant, and which could be tested by Stage 4 CMB experiments.
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