Dark Matter with Time-Varying Leptophilic Couplings
Hooman Davoudiasl
备注：
5 pages, Revtex 4. Estimates of possible gamma ray signals, a note regarding the recent Fermi-LAT results, and several new references added in this version
Two general problems arise when interpreting the recent cosmic ray data as signals of Dark Matter (DM) annihilation: (i) the required cross section is too large by O(100), and (ii) the annihilation products seem to be mostly leptonic. We propose to address these two problems by assuming that the couplings of DM to leptons grow with time. This can be achieved by a dynamic localization of DM in extra dimensions. A possible outcome of this proposal is a time (red-shift) dependent annihilation signal, in terms of strength and dominant final states.
Cosmic-ray positrons have long been considered a powerful probe of dark matter annihilation. In particular, myriad studies of the unexpected rise in the positron fraction have debated its dark matter or pulsar origins. In this paper, we instead examine the potential for extremely precise positron measurements by AMS-02 to probe hard leptophilic dark matter candidates that do not have spectral features similar to the bulk of the observed positron excess. Utilizing a detailed cosmic-ray propagation model that includes a primary positron flux generated by Galactic pulsars in addition to a seconda…
In leptophilic scenarios, dark matter interactions with nuclei, relevant for direct detection experiments and for the capture by celestial objects, could only occur via loop-induced processes. If the mediator is a scalar or pseudo-scalar particle, which only couples to leptons, the dominant contribution to dark matter-nucleus scattering would take place via two-photon exchange with a lepton triangle loop. The corresponding diagrams have been estimated in the literature under different approximations. Here, we present new analytical calculations for one-body two-loop and two-body one-loop inter…
We discuss model-independent collider constraints on the effective couplings of leptophilic dark matter (LDM), considering its production at a future electron-positron linear collider, with both polarized and unpolarized beam options, in the mono-photon and mono-$Z$ channels. We show that the future collider constraints are largely complementary to the direct and indirect detection limits on LDM, and can potentially provide the best-ever LDM sensitivity in the low-mass regime (below $\sim$ 10 GeV).
We propose a model which explains the baryon asymmetry of the universe and dark matter relic density at the same time. In this model, dark matter candidate is the dark baryon composed by dark quarks. A scalar mediator, which couples to the standard model leptons and dark quarks, is introduced to generate the asymmetry of baryon and dark baryon simultaneously. Direct detection and collider detection of this model are studied. We find that current underground direct detection experiments and LHC can hardly detect this model. But future lepton colliders, such as CEPC, have great potential to dete…
Inspired by the recently new measurement of $(g-2)_μ$ at FermiLab and reported upper bound for electron-dark matter (DM) recoil by the XENON1T collaboration, we revisited phenomenology of a light MeV scale vector dark matter in a leptophilic extension of standard model while a new spinor field plays the role of mediator. A viable parameter space is considered to discuss the possibility of light dark matter relic density as well as anomalous magnetic moment of the muon. We study DM-electron direct detection and cosmological bounds on the parameters space of the model. It is shown that although …
We study the influence of leptophilic dark matter interactions on decays of muons and ground state mesons in existing experiments. We consider a secluded dark sector exclusively interacting with leptons via either a (leptophilic) scalar or vector mediator. These interactions will therefore influence leptonic decays and deform the energy spectra. We first study the Michel decay of muons, $μ^+\rightarrow e^+ν_e \barν_μ$, which allow us to constrain the parameter space reasonably well. Secondly, the rare $π^\pm$, $K^\pm$, $D^\pm$ and $D_s^\pm$ decays to $eν$ will be considered. Scalar mediators w…
The muon $g-2$ anomaly was strengthened by recent experimental results at Fermilab, which may be signatures of new physics. A scenario of leptophilic scalar $ϕ_L$ accounting for the muon $g-2$ anomaly is investigated in this paper. Though a light $ϕ_L$ mainly decaying into standard model (SM) particles has been excluded by experiments, a dark leptophilic scalar $ϕ_L$ predominantly decaying into invisible fermionic dark matter (DM) $χ\barχ$ is still allowed. Considering the decay mode $ϕ_L \to χ\barχ$ opened (here $m_{ϕ_L} = 3 m_χ$), the coupling preferred by the muon $g-2$ and the $ϕ_L-χ$ coup…
We revisit dark matter annihilation as an explanation of the positron excess reported recently by the AMS-02 satellite-borne experiment. To this end, we propose a particle dark matter model by considering a Two Higgs Doublet Model (2HDM) extended with an additional singlet boson and a singlet fermion. The additional (light) boson mixes with the pseudoscalar inherent in the 2HDM, and the singlet fermion, which is the dark matter candidate, annihilates via this bosonic portal. The dark matter candidate is made leptophilic by choosing the lepton-specific 2HDM and a suitable high value of $\tanβ$.…
We consider the possibility that dark matter (DM) only interacts with the Standard Model leptons, but not quarks at tree level, and analyze the future lepton collider prospects of such leptophilic DM in the monophoton and mono-$Z$ (both leptonic and hadronic) channels. Adopting a model-independent effective field theory framework, we consider all possible dimension-six operators of scalar-pseudoscalar (SP), vector-axial vector (VA), and tensor-axial tensor (TAT) types for a fermionic DM and derive the collider sensitivities on the effective cutoff scale $Λ$ as a function of the DM mass. As a c…
We propose a new class of $U(1)_{μ-τ}$ gauged model that can explain recent flavor anomalies such as muon $g-2$, $b\to sμ^+ μ^-$, as well as include a scalar dark matter candidate while satisfying all the phenomenological constraints. For this purpose, we add new vectorlike quarks and leptons as well as two inert singlet scalars, one leptophilic and the other leptophobic. In our model $b\to sμ^+ μ^-$ anomalies can be explained by loop induced interactions among the SM and exotic quarks and $Z'$ gauge boson. In our numerical analysis, we show allowed region of our model to be narrow, and it wou…
We discuss the phenomenology of a minimal model for GeV-scale Majorana dark matter (DM) coupled to the standard model lepton sector via a charged scalar singlet. The theoretical framework extends the Standard Model by two $SU(2)_L$ singlets: one charged Higgs boson and a singlet right-handed fermion. The latter plays the role of the DM candidate. We show that there is an anti-correlation between the spin-independent DM-Nucleus scattering cross-section ($σ_{\rm SI}$) and the DM relic density. We suggest a scenario that can be tested in both electron-electron and electron-positron collisions usi…
Many scenarios of physics beyond the Standard Model predict the existence of new gauge singlets, which might be substantially lighter than the weak scale. The experimental constraints on additional scalars with masses in the MeV to GeV range could be significantly weakened if they interact predominantly with leptons rather than quarks. At an $e^+e^-$ collider, such a leptophilic scalar ($ϕ_L$) would be produced predominantly through radiation from a $τ$ lepton. We report herein a search for $e^+e^- \to τ^+τ^- ϕ_L$, $ϕ_L \to \ell^+\ell^-$ ($\ell=e,μ$) using data collected by the BABAR experimen…
Constraints on a Light Leptophilic Scalar from Dark-Sector Couplings
Physics Department and INFN Sezione di Roma, Università di Roma La Sapienza（罗马第一大学物理系及意大利国家核物理研究所罗马分部）；Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali di Frascati（意大利国家核物理研究所弗拉斯卡蒂国家实验室）；LAPTh, Université Savoie Mont-Blanc et CNRS（萨瓦蒙布朗大学与法国国家科学研究中心拉普特实验室）
