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 identify the model parameter space which explains the muon g-2 anomaly while evading the experimental constraints. After establishing the viability of the singlet fermion to be a dark matter candidate, we calculate the positron excess produced from its annihilation to the light bosons which primarily decay to muons. Incorporating the Sommerfeld effect caused by the light mediator and an appropriate boost factor, we find that our proposed model can satisfactorily explain the positron fraction excess as well as the positron spectrum data reported by AMS-02 experiment.
With the measurement of positron flux published recently by AMS-02 collaboration, we show how the leptophilic dark matter fits the observation. We obtain the percentages of different products of dark matter annihilation that can best describe the flux of high energy positrons observed by AMS. We show that dark matter annihilates predominantly into $ττ$ pair, while both $ee$ and $μμ$ final states should be less than $20\%$. When gauge boson final states are included, the best branching ratio of needed $ττ$ mode reduces.
The annihilation of dark matter particles in the galactic halo of the Milky Way may lead to cosmic ray signatures that can be probed by the AMS-02 experiment, which has measured the composition and fluxes of charged cosmic rays with unprecedented precision. Given the absence of characteristic spectral features in the electron and positron fluxes measured by AMS-02, we derive upper limits on the dark matter annihilation cross section for leptophilic dark matter models. Our limits are based on a new background model that describes all recent measurements of the energy spectra of cosmic ray posit…
Positron excess upto energies $\sim$350 GeV has been observed by AMS-02 result and it is consistent with the positron excess observed by PAMELA upto 100 GeV. There is no observed excess of anti-protons over the expected CR background. We propose a leptophilic dark matter with an $U(1)_{L_μ-L_τ}$ gauge extension of MSSM. The dark matter is an admixture of the $L_μ-L_τ$ gaugino and fermionic partners of the extra $SU(2)$ singlet Higgs boson, which break the $L_μ-L_τ$ symmetry. We construct the SM$\otimes U(1)_{ L_μ-L_τ}$ SUSY model which provides the correct relic density of dark matter and is c…
In this paper we revisit constraints on the leptophilic dark matter (DM) arising from the DM indirect detection experiments. Interactions between the charged leptons and the scalar-type, Dirac-type or vector-type DM are written in terms of effective operators. After classifying all interactions that may give non-zero signals in indirect detections, we study constraints on the parameter space of these effective interactions from the latest results of AMS-02, Planck, Fermi-LAT and H.E.S.S., as well as the observed relic abundance. Main results are summarized in the Table. I. It shows that the $τ…
The Standard Model (SM) supplemented by Type II Seesaw and a SM gauge-singlet scalar dark matter (DM) is a very simple framework to incorporate the observed neutrino oscillations and provide a plausible DM candidate. In this framework, the scalar DM naturally has a leptophilic nature with a pair annihilating mainly into the SM SU(2)$_L$ triplet Higgs scalar of Type II Seesaw which, in turn, decay into leptons. In this work, we consider indirect signatures of this leptophilic DM and examine the spectrum of the cosmic ray electron/positron flux from DM pair annihilations in the Galactic halo. Gi…
We perform a detailed study of scalar dark matter with triplet Higgs extensions of the Standard Model in order to explain the cosmic ray electron and positron excesses reported by AMS-02 and DAMPE. A detailed analysis of AMS-02 positron excess reveals that for different orderings (normal, inverted and quasi-degenerate) of neutrino mass, the hybrid triplet Higgs portal framework is more favored with respect to the single triplet Higgs portal for TeV scale dark matter. We also show that the resonant peak and continuous excess in DAMPE cosmic ray data can be well explained with the hybrid triplet…
A light leptophilic boson (scalar or pseudoscalar) has been postulated to explain the muon g-2 anomaly and could be a portal to dark matter. Realizing the leptophilic nature of a singlet boson in the framework of the two-Higgs-doublet-Model of type-X, we identify the parameter space viable for the explanation of the updated muon g-2 discrepancy. It is then shown that such a hypothetical particle will be unambiguously ruled out or discovered via the Yukawa process at a lepton collider designed as a Higgs factory.
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 a Dark left-right gauge model, the neutral component of right-handed lepton doublet is odd under generalized R-parity and thus the lightest one serves as the dark matter (DM) candidate. The coannihilation of the dark matter with the singly charged Higgs triplet produces the correct relic abundance. We explain AMS-02 positron excess by the annihilation of 800 GeV dark matter into $μ^+μ^-γ$, through a t-channel exchange of the additional charged triplet Higgs boson. The DM is leptophilic which is useful for explaining the non-observation of any antiproton excess which would generically be exp…
We study vector portal dark matter models where the mediator couples only to leptons. In spite of the lack of tree-level couplings to colored states, radiative effects generate interactions with quark fields that could give rise to a signal in current and future experiments. We identify such experimental signatures: scattering of nuclei in dark matter direct detection; resonant production of lepton-antilepton pairs at the Large Hadron Collider; and hadronic final states in dark matter indirect searches. Furthermore, radiative effects also generate an irreducible mass mixing between the vector …
We investigate a beyond standard model (SM) portal scenario for dark matter (DM) particle with leptoquark being the mediator field. Leptoquark, a colored particle having both baryon and lepton number, allows the DM to interact with the SM fields via renormalizable interaction. By focusing on a vector leptoquark portal with Majorana fermion DM candidate, we find the only unknown coupling in the model is sensitive to all three main features of a DM model namely, relic density, direct detection as well as indirect detection, while being consistent with collider data. We explore the parameter spac…
We investigate the scenario where the dark matter only interacts with the charged leptons in the standard model via a neutral vector mediator $Z'$. Such a scenario with a 430 GeV dark matter can fit the recent positron fluxes observed by the AMS-02 Collaborations, with the reasonable boost factors. We study the possibility of searching such leptophilic $Z'$ via its lepton final states and invisible decay modes at the future electron-positron colliders, such as the International Linear Collider (ILC) and the Compact Linear Collider (CLIC). We find that for the benchmark models with $Z'$ mass fr…
Sterile neutrinos could provide a link between the Standard Model particles and a dark sector, besides generating active neutrino masses via the seesaw mechanism type I. We show that, if dark matter annihilation into sterile neutrinos determines its observed relic abundance, it is possible to explain the Galactic Center $γ$-ray excess reported by the Fermi-LAT Collaboration as due to an astrophysical component plus dark matter annihilations. We observe that sterile neutrino portal to dark matter provides an impressively good fit, with a p-value of 0.78 in the best fit point, to the Galactic Ce…
Dark matter (DM) constitutes 85% of the matter in the Universe. However, its specific particle property is still unclear. The fundamentals of DM particles subject to gravitational interaction, and that the lepton excess in cosmic rays may originate from DM particles, inspired us to investigate DM particle properties beyond the standard model. We assume that a leptophilic SU(2) doublet exists in nature as the mediator connecting DM with visible leptons. Since general relativity is not renormalizable at the quantum level, it should be regarded as an effective field theory's leading order term. O…
We investigate the indirect signatures of the Higgs portal $U(1)_X$ vector dark matter (VDM) $X_μ$ from both its pair annihilation and decay. The VDM is stable at renormalizable level by $Z_2$ symmetry, and thermalized by Higgs-portal interactions. It can also decay by some nonrenormalizable operators with very long lifetime at cosmological time scale. If dim-6 operators for VDM decays are suppressed by $10^{16}$ GeV scale, the lifetime of VDM with mass $\sim$ 2 TeV is just right for explaining the positron excess in cosmic ray recent observed by PAMELA and AMS02 Collaborations. The VDM decayi…
The scalar Higgs portal is a compelling model of dark matter (DM) in which a renormalizable coupling with the Higgs boson provides the connection between the visible world and the dark sector. In this paper we investigate the constraint placed on the parameter space of this model by the antiproton data. Due to the fact that the antiproton-to-proton ratio has relative less systematic uncertainties than the antiproton absolute flux, we propose and explore the possibility to combine all the available $\bar{p}/p$ data. Following this approach, we are able to obtain stronger limits if compared with…
We show that the cosmic-ray positron excess measured by PAMELA and AMS could be induced by Dark Matter annihilations in a local over-density. In such a context leptophilic DM is not needed and good fits to positron data, in agreement with antiproton and gamma-ray measurements, are obtained for DM annihilations to $WW$, $hh$, $ZZ$, $ t \bar t$, $b \bar b$, $q\bar q$ channels. The classic Dark Matter candidates, such as the pure supersymmetric Wino with standard thermal annihilation cross-section, can fit the positron excess, without invoking any additional assumption on Dark Matter properties.
We study a simple extension of the Standard Model supplemented by an electroweak triplet scalar field to accommodate small neutrino masses by the type-II seesaw mechanism, while an additional singlet scalar field can play the role of cold dark matter (DM) in our Universe. This DM candidate is leptophilic for a wide range of model parameter space, and the lepton flux due to its annihilation carries information about the neutrino mass hierarchy. Using the recently released high precision data on positron fraction and flux from the AMS-02 experiment, we examine the DM interpretation of the observ…
Positron excess observed by PAMELA, Fermi and AMS02 may be due to dark matter (DM) pair annihilation or decay dominantly into muons. In this paper, we consider a scenario with thermal fermionic DM ($χ$) with mass $\sim O(1-2)$ TeV decaying into a dark Higgs ($ϕ$) and an active neutrino ($ν_a$) instead of the SM Higgs boson and $ν_a$. We first present a renormalizable model for this scenario with local dark $U(1)_X$ gauge symmetry, in which the DM $χ$ can be thermalized by Higgs portal and the gauge kinetic mixing. Assuming the dark Higgs ($ϕ$) mass is in the range $2 m_μ< m_ϕ< 2 m_{π^0}$, the …
We have witnessed in the past decade the observation of a puzzling cosmic-ray excess at energies larger than $10$ GeV. The AMS-02 data published this year has new ingredients such as the bump around $300$ GeV followed by a drop at $800$ GeV, as well as smaller error bars. Adopting the background used by the AMS-02 collaboration in their analysis, one can conclude that previous explanations to the new AMS-02 such as one component annihilating and decaying dark matter as well as pulsars seem to fail at reproducing the data. Here, we show that in the right-handed neutrino portal might reside the …
Global symmetry can guarantee the stability of dark matter particles (DMps). However, the nonminimal coupling between dark matter (DM) and gravity can destroy the global symmetry of DMps, which in turn leads to their decay. Under the framework of nonminimal coupling between scalar singlet dark matter (ssDM) and gravity, it is worth exploring to what extent the symmetry of ssDM is broken. It is suggested that the total amount of decay products of ssDM cannot exceed current observational constraints. Along these lines, the data obtained with satellites such as Fermi-LAT and AMS-02 can limit the …
Mono-Z signal for dark matter searches at future lepton colliders and cosmological interpretation
Indian Institute of Technology Guwahati（印度理工学院古瓦哈提分校）；Indian Institute of Technology Hyderabad（印度理工学院海得拉巴分校）；Université Grenoble-Alpes（格勒诺布尔阿尔卑斯大学）；Indian Institute of Technology Kanpur（印度理工学院坎普尔分校）；Indian Institute of Science Education and Research Thiruvananthapuram（印度科学与教育研究所特里凡得琅分校）；University of the Witwatersrand（威特沃特斯兰德大学）；SGTB Khalsa College, University of Delhi（德里大学 SG TB 卡尔萨学院）
We study a vector dark matter (VDM) model in which the dark sector couples to the Standard Model sector via a Higgs portal. If the portal coupling is small enough the VDM can be produced via the freeze-in mechanism. It turns out that the electroweak phase transition have a substantial impact on the prediction of the VDM relic density. We further assume that the dark Higgs boson which gives the VDM mass is so light that it can induce strong VDM self-interactions and solve the small-scale structure problems of the Universe. As illustrated by the latest LUX data, the extreme smallness of the Higg…
An excess of gamma rays at GeV energies has been pointed out in the Fermi-LAT data. This signal comes from a narrow region centred around the Galactic center and has been interpreted as possible evidence for light dark matter particles annihilating either into a mixture of leptons-antileptons and b-bbar or into b-bbar only. Focusing on the prompt gamma-ray emission, previous works found that the best fit to the data corresponds to annihilations proceeding predominantly into b-bbar. However, here we show that omitting the photon emission originating from primary and secondary electrons produced…
The PAMELA and Fermi measurements of the cosmic-ray electron and positron spectra have generated much interest over the past two years, because they are consistent with a significant component of the electron and positron fluxes between 20 GeV and 1 TeV being produced through dark matter annihilation or decay. However, since the measurements are also consistent with astrophysical interpretations, the message is unclear. In this paper, we point out that dark matter can have a more distinct signal in cosmic rays, that of a charge asymmetry. Such charge asymmetry can result if the dark matter's a…
A possible hint of dark matter annihilation has been found in Cuoco, Korsmeier and Krämer (2017) from an analysis of recent cosmic-ray antiproton data from AMS-02 and taking into account cosmic-ray propagation uncertainties by fitting at the same time dark matter and propagation parameters. Here, we extend this analysis to a wider class of annihilation channels. We find consistent hints of a dark matter signal with an annihilation cross-section close to the thermal value and with masses in range between 40 and 130 GeV depending on the annihilation channel. Furthermore, we investigate in how fa…
Direct searches for WIMPs are sensitive to physics well below the weak scale. In the absence of light mediators, it is fruitful to apply an Effective Field Theory (EFT) approach accounting only for dark matter (DM) interactions with Standard Model (SM) fields. We consider a singlet fermion WIMP and effective operators up to dimension 6 which are generated at the mass scale of particles mediating DM interactions with the SM. We perform a one-loop Renormalization Group Evolution (RGE) analysis, evolving these effective operators from the mediators mass scale to the nuclear scales probed by direc…
