Two dark matter components in N_{DM}MSSM and dark matter extension of the minimal supersymmetric standard model and the high energy positron spectrum in PAMELA/HEAT data
We present the dark matter (DM) extension (by N) of the minimal supersymmetric standard model to give the recent trend of the high energy positron spectrum of the PAMELA/HEAT experiments. If the trend survives by future experiments, the MSSM needs to be extended. Here, we minimally extend the MSSM with one more DM component N together with a heavy lepton E, and introduce the coupling e_R E_R^c N_R. This coupling naturally appears in the flipped SU(5) GUT models. This N_{DM}MSSM contains the discrete symmetry Z_6, and for some parameter ranges there result two DM components. For the MSSM fields, the conventional R-parity, which is a subgroup of Z_6, is preserved. We also present the needed parameter ranges of these additional particles.
Motivated by the anomalous positron flux recently reported by the PAMELA collaboration, we study the cosmic-ray positron produced by the pair annihilation and the decay of superparticle dark matter. We calculate the cosmic-ray positron flux and discuss implications of the PAMELA data. We show that the positron excess observed by the PAMELA can be explained with some of the superparticle dark matter.
We present Minimal Dark Matter and its univocal predictions for Dark Matter observables. During the idm2008 conference, PAMELA presented preliminary results showing an excess in the positron fraction: we find a good agreement, with a modest astrophysical boost factor.
Recently PAMELA released their first results on the positron and antiproton ratios. Stimulated by the new data, we studied the cosmic ray propagation models and calculated the secondary positron and antiproton spectra. The low energy positron ratio can be consistent with data in the convection propagation model. Above $\sim 10$ GeV PAMELA data shows a clear excess on the positron ratio. However, the secondary antiproton is roughly consistent with data. The positron excess may be a direct evidence of dark matter annihilation or decay. We compare the positron and anti-proton spectra with data by…
Recently published results from the PAMELA experiment have shown conclusive evidence for an excess of positrons at high (~ 10 - 100 GeV) energies, confirming earlier indications from HEAT and AMS-01. Such a signal is generally expected from dark matter annihilations. However, the hard positron spectrum and large amplitude are difficult to achieve in most conventional WIMP models. The absence of any associated excess in anti-protons is highly constraining on any model with hadronic annihilation modes. We revisit an earlier proposal, whereby the dark matter annihilates into a new light (<~GeV) b…
Astrophysical and cosmological observations do not require the dark matter particles to be absolutely stable. If they are indeed unstable, their decay into positrons might occur at a sufficiently large rate to allow the indirect detection of dark matter through an anomalous contribution to the cosmic positron flux. In this paper we discuss the implications of the excess in the positron fraction recently reported by the PAMELA collaboration for the scenario of decaying dark matter. To this end, we have performed a model-independent analysis of possible signatures by studying various decay chann…
The space-borne antimatter experiment PAMELA has recently reported a surprising rise in the positron to electron ratio at high energies. It has also recently been found that electromagnetic radiative corrections in some cases may boost the gamma-ray yield from supersymmetric dark matter annihilations in the galactic halo by up to three or four orders of magnitude, providing distinct spectral signatures for indirect dark matter searches to look for. Here, we investigate whether the same type of corrections can also lead to sizeable enhancements in the positron yield. We find that this is indeed…
Recently the PAMELA satellite-based experiment reported an excess of galactic positrons that could be a signal of annihilating dark matter. The PAMELA data may admit an interpretation as a signal from a wino-like LSP of mass about 200 GeV, normalized to the local relic density, and annihilating mainly into W-bosons. This possibility requires the current conventional estimate for the energy loss rate of positrons be too large by roughly a factor of five. Data from anti-protons and gamma rays also provide tension with this interpretation, but there are significant astrophysical uncertainties ass…
We take the MSSM as a complete theory of low energy phenomena, including neutrino masses and mixings. This immediately implies that the gravitino is the only possible dark matter candidate. We study the implications of the astrophysical experiments such as PAMELA and Fermi-LAT, on this scenario. The theory can account for both the realistic neutrino masses and mixings, and the PAMELA data as long as the slepton masses lie in the $500-10^6 $TeV range. The squarks can be either light or heavy, depending on their contribution to radiative neutrino masses. On the other hand, the Fermi-LAT data imp…
We consider a scenario within the Minimal Supersymmetric Standard Model extended by a singlet chiral superfield, in which neutralino dark matter annihilates to light singlet-like Higgs bosons, which proceed to decay to either electron-positron or muon-antimuon pairs. Unlike neutralino annihilations in the MSSM, this model can provide a good fit to the PAMELA cosmic ray positron fraction excess. Furthermore, the singlet-like scalar Higgs can induce a large Sommerfeld enhancement and provide an annihilation rate sufficient to accommodate the observed positron excess.
The recent positron excess observed in the PAMELA satellite experiment strengthens previous experimental findings. We give here an analysis of this excess in the framework of the Stueckelberg extension of the standard model which includes an extra $U(1)_X$ gauge field and matter in the hidden sector. Such matter can produce the right amount of dark matter consistent with the WMAP constraints. Assuming the hidden sector matter to be Dirac fermions it is shown that their annihilation can produce the positron excess with the right positron energy dependence seen in the HEAT, AMS and the PAMELA ex…
The recent data from PAMELA and Fermi-LAT can be interpreted as evidence of new astrophysical sources of high energy positrons. In that case, such astrophysical positrons constitute an additional background against the positrons from dark matter annihilation. In this paper, we study the effect of that background on the prospects for the detection of a positron dark matter signal in future experiments. In particular, we determine the new regions in the (mass, $\sigmav$) plane that are detectable by the AMS-02 experiment for several dark matter scenarios and different propagation models. We find…
We extract the positron and electron fluxes in the energy range 10 - 100 GeV by combining the recent data from PAMELA and Fermi LAT. The {\it absolute positron and electron} fluxes thus obtained are found to obey the power laws: $E^{-2.65}$ and $E^{-3.06}$ respectively, which can be confirmed by the upcoming data from PAMELA. The positron flux appears to indicate an excess at energies $E\gsim 50$ GeV even if the uncertainty in the secondary positron flux is added to the Galactic positron background. This leaves enough motivation for considering new physics, such as annihilation or decay of dar…
We study the indirect detection of neutralino dark matter using positrons and gamma rays from its annihilation in the galactic halo. Considering the HESS data as the spectrum constituting the gamma--ray background, we compare the prospects for the experiments GLAST and PAMELA in a general supergravity framework with non--universal scalar and gaugino masses. We show that with a boost factor of about 10, PAMELA will be competitive with GLAST for typical NFW cuspy profiles.
We show that R-parity violating decay of Wino dark matter of mass \sim 3 TeV can naturally account for the flux and spectral shape of the cosmic-ray electrons and positrons observed by the PAMELA and Fermi satellites. To provide a theoretical basis for the scenario, we also present a model that trilinear R-parity breaking appears with a coefficient suppressed by powers of the gravitino mass, which naturally leads to the Wino lifetime of O(10^26) sec.
Secondary positrons are produced by spallation of cosmic rays within the interstellar gas. Measurements have been typically expressed in terms of the positron fraction, which exhibits an increase above 10 GeV. Many scenarios have been proposed to explain this feature, among them some additional primary positrons originating from dark matter annihilation in the Galaxy. The PAMELA satellite has provided high quality data that has enabled high accuracy statistical analyses to be made, showing that the increase in the positron fraction extends up to about 100 GeV. It is therefore of paramount impo…
We propose a new class of R-parity violating extension of MSSM with type II seesaw mechanism for neutrino masses where an unstable gravitino is the dark matter of the Universe. It decays predominantly into three leptons final states, thereby providing a natural explanation of the positron excess but no antiproton excess in the PAMELA experiment. The model can explain neutrino masses without invoking any high scale physics while keeping the pre-existing baryon asymmetry of the universe in tact.
We discuss the synchrotron radiation flux from the Galactic center in unstable dark matter scenario. Motivated by the anomalous excess of the positron fraction recently reported by the PAMELA collaboration, we consider the case that the dark matter particle is unstable (and long-lived), and that energetic electron and positron are produced by the decay of dark matter. Then, the emitted electron and positron becomes the source of the synchrotron radiation. We calculate the synchrotron radiation flux for models of decaying dark matter, which can explain the PAMELA positron excess. Taking the lif…
We provide a scenario in which a hidden U(1) gauge boson constitutes dark matter of the Universe and decays into the standard-model particles through a kinetic mixing with an $U(1)_{B-L}$ gauge boson. Interestingly, our model can naturally account for the steep rise in the positron fraction recently reported by PAMELA. Moreover, we find that due to the charge assignment of $U(1)_{B-L}$, only a small amount of antiprotons are produced in the decay, which is also consistent with the PAMELA and other observational data.
As discussed recently by Hooper and Tait, the singlino-like dark matter in the Minimal Supersymmetric Standard Model (MSSM) extended by a singlet Higgs superfield can give a perfect explanation for both the relic density and the Pamela result through the Sommerfeld-enhanced annihilation into singlet Higgs bosons ($a$ or $h$ followed by $h->a a$) with $a$ being light enough to decay dominantly to muons or electrons. In this work we analyze the parameter space required by such a dark matter explanation and also consider the constraints from the LEP experiments. We find that although the light si…
The excess in the positron fraction reported by the PAMELA collaboration has been interpreted as due to annihilation or decay of dark matter in the Galaxy. More prosaically, it has been ascribed to direct production of positrons by nearby pulsars, or due to pion production during stochastic acceleration of hadronic cosmic rays in nearby sources. We point out that measurements of secondary nuclei produced by cosmic ray spallation can discriminate between these possibilities. New data on the titanium-to-iron ratio from the ATIC-2 experiment support the hadronic source model above and enable a pr…
We propose two viable scenarios explaining the recent observations on cosmic positron excess. In both scenarios, the present relic density in the Universe is assumed to be still supported by thermally produced WIMP or LSP (χ). One of the scenarios is based on two dark matter (DM) components (χ,X) scenario, and the other is on SO(10) SUSY GUT. In the two DM components scenario, extremely small amount of non-thermally produced meta-stable DM component [O(10^{-10}) < n_X /n_χ] explains the cosmic positron excess. In the SO(10) model, extremely small R-parity violation for LSP decay to e^\pm is na…
Recently, there are two hints arising from physics beyond the standard model. One is a possible energy loss mechanism due to emission of very weakly interacting light particles from white dwarf stars, with a coupling strength ~ 0.7x10^{-13}, and another is the high energy positrons observed by the PAMELA satellite experiment. We construct a supersymmetric flipped-SU(5) model, SU(5)xU(1)_X with appropriate additional symmetries, [U(1)_H]_{gauge}x[U(1)_RxU(1)_Γ]_{global}xZ_2, such that these are explained by a very light electrophilic axion of mass 0.5 meV from the spontaneously broken U(1)_Γand…
Motivated by the recent results from the PAMELA and ATIC, we study the cosmic-ray electron and positron produced by the decay of gravitino dark matter. We calculate the cosmic-ray electron and positron fluxes and discuss implications to the PAMELA and ATIC data. In this paper, we will show that the observed anomalous fluxes by the PAMELA and ATIC can be explained in such a scenario. We will also discuss the synchrotron radiation flux from the Galactic center in such a scenario.
Recent PAMELA data show that positron fraction has an excess above several GeV while anti-proton one is not. Moreover ATIC data indicates that electron/positron flux have a bump from 300 GeV to 800 GeV. Both annihilating dark matter (DM) with large boost factor and decaying DM with the life around $ 10^{26} s$ can account for the PAMELA and ATIC observations if their main final products are charged leptons ($e$, $μ$ and $τ$). In this work, we calculated the neutrino flux arising from $μ$ and $τ$ which originate from annihilating/decaying DM, and estimated the final muon rate in the neutrino te…
We consider the signals of positrons and electrons from "exciting" dark matter (XDM) annihilation. Because of the light (m_phi ~< 1 GeV) force carrier phi into which the dark matter states can annihilate, the electrons and positrons are generally very boosted, yielding a hard spectrum, in addition to the low energy positrons needed for INTEGRAL observations of the galactic center. We consider the relevance of this scenario for HEAT, PAMELA and the WMAP "haze," focusing on light (m_phi ~< 2 m_pi) phi bosons, and find that significant signals can be found for all three, although significant sign…
We calculate the extragalactic diffuse emission originating from the up-scattering of cosmic microwave photons by energetic electrons and positrons produced in particle dark matter annihilation events at all redshifts and in all halos. We outline the observational constraints on this emission and we study its dependence on both the particle dark matter model (including the particle mass and its dominant annihilation final state) and on assumptions on structure formation and on the density profile of halos. We find that for low-mass dark matter models, data in the X-ray band provide the most st…
We present a simple model in which dark matter couples to the standard model through a light scalar intermediary that is itself unstable. We find this model has several notable features, and allows a natural explanation for a surplus of positrons, but no surplus of anti-protons, as has been suggested by early data from PAMELA and ATIC. Moreover, this model yields a very small nucleon coupling, well below the direct detection limits. In this paper we explore the effect of this model in both the early universe and in the galaxy.
A series of experiments measuring high-energy cosmic rays have recently reported strong indications for the existence of an excess of high-energy electrons and positrons. If interpreted in terms of the decay of dark matter particles, the PAMELA measurements of the positron fraction and the Fermi LAT measurements of the total electron-plus-positron flux restrict the possible decaying dark matter scenarios to a few cases. Analyzing different decay channels in a model-independent manner, and adopting a conventional diffusive reacceleration model for the background fluxes of electrons and positron…
In this letter, we suggest that a nearby clump of 600-1000 GeV neutralinos may be responsible for the excesses recently observed in the cosmic ray positron and electron spectra by the PAMELA and ATIC experiments. Although neutralino dark matter annihilating throughout the halo of the Milky Way is predicted to produce a softer spectrum than is observed, and violate constraints from cosmic ray antiproton measurements, a large nearby (within 1-2 kiloparsecs of the Solar System) clump of annihilating neutralinos can lead to a spectrum which is consistent with PAMELA and ATIC, while also producing …
We examine whether the cosmic ray positron excess observed by PAMELA can be explained by neutralino annihilation in the Next-to-Minimal Supersymmetric Standard Model (NMSSM). The main dark matter annihilation products are the lightest CP-even scalar h1 plus the lightest CP-odd scalar a1, with the a1 decaying into two muons. The energetic positrons needed to explain PAMELA are thus obtained in the NMSSM simply from kinematics. The required large annihilation cross section is obtained from an s-channel resonance with the heavier CP-odd scalar a2. Various experiments constrain the PAMELA-favored …
Assuming that the positron excess in PAMELA satellite data is a consequence of annihilations of cold dark matter, we consider from a model-independent perspective if the data show a preference for the spin of dark matter. We then perform a general analysis of annihilations into two-body final states to determine what weighted combination of channels best describes the data.
PAMELA's observation that the cosmic ray positron fraction increases rapidly with energy implies the presence of primary sources of energetic electron-positron pairs. Of particular interest is the possibility that dark matter annihilations in the halo of the Milky Way provide this anomalous flux of antimatter. The recent measurement of the cosmic ray electron spectrum by the Fermi Gamma Ray Space Telescope, however, can be used to constrain the nature of any such dark matter particle. In particular, it has been argued that in order to accommodate the observations of Fermi and provide the PAMEL…
A new calculation of the $\bar{p}/p$ ratio in cosmic rays is compared to the recent PAMELA data. The good match up to 100 GeV allows to set constraints on exotic contributions from thermal WIMP dark matter candidates. We derive stringent limits on possible enhancements of the WIMP \pbar flux: a $m_{\rm WIMP}$=100 GeV (1 TeV) signal cannot be increased by more than a factor 6 (40) without overrunning PAMELA data. Annihilation through the $W^+W^-$ channel is also inspected and cross-checked with $e^+/(e^-+e^+)$ data. This scenario is strongly disfavored as it fails to simultaneously reproduce po…
Recent results from the PAMELA satellite indicate the presence of a large flux of positrons (relative to electrons) in the cosmic ray spectrum between approximately 10 and 100 GeV. As annihilating dark matter particles in many models are predicted to contribute to the cosmic ray positron spectrum in this energy range, a great deal of interest has resulted from this observation. Here, we consider pulsars (rapidly spinning, magnetized neutron stars) as an alternative source of this signal. After calculating the contribution to the cosmic ray positron and electron spectra from pulsars, we find th…
We argue that both the positron fraction measured by PAMELA and the peculiar spectral features reported in the total electron-positron (e+e-) flux measured by ATIC have a very natural explanation in electron-positron pairs produced by nearby pulsars. While this possibility was pointed out a long time ago, the greatly improved quality of current data potentially allow to reverse-engineer the problem: given the regions of pulsar parameter space favored by PAMELA and by ATIC, are there known pulsars that explain the data with reasonable assumptions on the injected e+e- pairs? In the context of si…
We discuss recent observations of high energy cosmic ray positrons and electrons in the context of hadronic interactions in supernova remnants, the suspected accelerators of galactic cosmic rays. Diffusive shock acceleration can harden the energy spectrum of secondary positrons relative to that of the primary protons (and electrons) and thus explain the rise in the positron fraction observed by PAMELA above 10 GeV. We normalize the hadronic interaction rate by holding pion decay to be responsible for the gamma-rays detected by HESS from some SNRs. By simulating the spatial and temporal distrib…
We analyze the cosmic-ray signatures of decaying gravitino dark matter in a model independent way based on an operator analysis. Thermal leptogenesis and universal boundary conditions at the GUT scale restrict the gravitino mass to be below 600 GeV. Electron and positron fluxes from gravitino decays, together with the standard GALPROP background, cannot explain both, the PAMELA positron fraction and the electron + positron flux recently measured by Fermi LAT. For gravitino dark matter, the observed fluxes require astrophysical sources. The measured antiproton flux allows for a sizable contribu…
Dark matter particles annihilating in the Galactic halo can provide a flux of positrons potentially observable in upcoming experiments, such as PAMELA and AMS-02. We discuss the spectral features which may be associated with dark matter annihilation in the positron spectrum and assess the prospects for observing such features in future experiments. Although we focus on some specific dark matter candidates, neutralinos and Kaluza-Klein states, we carry out our study in a model independent fashion. We also revisit the positron spectrum observed by HEAT.
Recent measurements of cosmic-ray electron and positron fluxes by PAMELA and ATIC experiments may indicate the existence of annihilating dark matter with large annihilation cross section. We discuss its possible relation to other astrophysical/cosmological observations : gamma-rays, neutrinos, and big-bang nucleosynthesis. It is shown that they give stringent constraints on some annihilating dark matter models.
X-ray and gamma-ray observations can help understand the origin of the electron and positron signals reported by ATIC, PAMELA, PPB-BETS, and Fermi. It remains unclear whether the observed high-energy electrons and positrons are produced by relic particles, or by some astrophysical sources. To distinguish between the two possibilities, one can compare the electron population in the local neighborhood with that in the dwarf spheroidal galaxies, which are not expected to host as many pulsars and other astrophysical sources. This can be accomplished using X-ray and gamma-ray observations of dwarf …
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…
We show that the anomaly of the positron fraction observed by the PAMELA experiment can be attributed to recent supernova explosion(s) in a dense gas cloud (DC) near the Earth. Protons are accelerated around the supernova remnant (SNR). Electrons and positrons are created through hadronic interactions inside the DC. Their spectrum is harder than that of the background because the SNR spends much time in a radiative phase. Our scenario predicts that the anti-proton flux dominates that of the background for >~100 GeV. We compare the results with observations (Fermi, HESS, PPB-BETS, and ATIC).
We suppose that the lightest supersymmetric particle (LSP) in the minimal supersymmetric standard model (MSSM) is the dark matter. The bino-like LSP can decay through the SO(10) gauge interactions, if one right-handed (RH) neutrino (ν^c_1) is lighter than the LSP and its superpartner (\tildeν^c_1) develops a vacuum expectation value (VEV), raising extremely small R-parity violation naturally. The leptonic decay modes can be dominant, if the VEV scale of {\bf 16}_H is a few orders of magnitude lower than the VEV of {\bf 45}_H (\approx 10^{16} GeV), and if a slepton (\tilde{e}^c_1) is relatively…
It is shown that a Weakly Interacting Massive dark matter Particle (WIMP) interpretation for the positron excess observed in a variety of experiments, HEAT, PAMELA, and AMS-02, is highly constrained by the Fermi/LAT observations of dwarf galaxies. In particular, this paper has focused on the annihilation channels that best fit the current AMS-02 data (Boudaud et al., 2014). The Fermi satellite has surveyed the $γ$-ray sky, and its observations of dwarf satellites are used to place strong bounds on the annihilation of WIMPs into a variety of channels. For the single channel case, we find that d…
We explain the PAMELA positron excess and the PPB-BETS/ATIC e+ + e- data using a simple two component dark matter model (2DM). The two particle species in the dark matter sector are assumed to be in thermal equilibrium in the early universe. While one particle is stable and is the present day dark matter, the second one is metastable and decays after the universe is 10^-8 s old. In this model it is simple to accommodate the large boost factors required to explain the PAMELA positron excess without the need for large spikes in the local dark matter density. We provide the constraints on the par…
Dark Matter annihilation (DMA) may yield an excess of gamma rays and antimatter particles, like antiprotons and positrons, above the background from cosmic ray interactions. The excess of diffuse Galactic Gamma Rays from EGRET shows all the features expected from DMA. The new precise measurements of the antiproton and positron fractions from PAMELA are compared with the EGRET excess. It is shown that the charged particles are strongly dependent on the propagation model used. The usual propagation models with isotropic propagation models are incompatible with the recently observed convection in…
Excitation of multicomponent dark matter in the galactic center has been proposed as the source of low-energy positrons that produce the excess 511 keV gamma rays that have been observed by INTEGRAL. Such models have also been promoted to explain excess high-energy electrons/positrons observed by the PAMELA, Fermi/LAT and H.E.S.S. experiments. We investigate whether one model can simultaneously fit all three anomalies, in addition to further constraints from inverse Compton scattering by the high-energy leptons. We find models that fit both the 511 keV and PAMELA excesses at dark matter masses…
In this note we briefly review the recent studies of dark matter in the MSSM and its singlet extensions: the NMSSM, the nMSSM, and the general singlet extension. Under the new detection results of CDMS II, XENON, CoGeNT and PAMELA, we find that (i) the latest detection results can exclude a large part of the parameter space which allowed by current collider constraints in these models. The future SuperCDMS and XENON can cover most of the allowed parameter space; (ii) the singlet sector will decouple from the MSSM-like sector in the NMSSM, however, singlet sector makes the nMSSM quite different…
We propose a model of dark matter identified with a pseudo-Nambu-Goldstone boson in the dynamical supersymmetry breaking sector in a gauge mediation scenario. The dark matter particles annihilate via a below-threshold narrow resonance into a pair of R-axions each of which subsequently decays into a pair of light leptons. The Breit-Wigner enhancement explains the excess electron and positron fluxes reported in the recent cosmic ray experiments PAMELA, ATIC and PPB-BETS without postulating an overdensity in halo, and the limit on anti-proton flux from PAMELA is naturally evaded.
Many different mechanisms can contribute to antiprotons and positrons production, ranging from conventional reactions up to exotic processes like neutralino annihilation. The open problems are so fundamental (i.e.: is the universe symmetric in matter and antimatter ?) that experiments in this field will probably be of the greatest interest in the next years. Here we will summarize the present situation, showing the different hypothesis and models and the experimental measurements needed to lead to a more established scenario.
The positron excess observed by the PAMELA experiment may come from dark matter annihilation, if the annihilation cross section is large enough. We show that the dark matter annihilation scenarios to explain the positron excess may also be compatible with the discrepancy of the cosmic lithium abundances between theory and observations. The wino-like neutralino in the supersymmetric standard model is a good example for it. This scenario may be confirmed by Fermi satellite experiment.
We calculate the flux of cosmic positrons from the dark matter annihilation in the littlest Higgs model with T-parity. The dark matter annihilates mainly into weak gauge bosons in the halo, and high energy positrons are produced through leptonic and hadronic decays of the bosons. We investigate a possibility to detect the positron signal in upcoming experiments such as PAMELA and AMS-02. We found that the dark matter signal can be distinguished from the background in the PAMELA experiment when the dark matter mass is less than 120 GeV and the signal flux is enhanced due to a small scale cluste…
We study a scenario that a U(1) hidden gaugino constitutes the dark matter in the Universe and decays into a lepton and slepton pair through a mixing with a U(1)B-L gaugino. We find that the dark-matter decay can account for the recent PAMELA and ATIC anomalies in the cosmic-ray positrons and electrons without an overproduction of antiprotons.
The excess of cosmic-ray electron and positron fluxes measured by the PAMELA satellite and ATIC balloon experiments may be interpreted as the signals of the dark matter annihilation or decay into leptons. In this letter we show that the dark matter annihilation/decay which reproduces the electron/positron excess may yield a significant amount of high-energy neutrinos from the Galactic center. In the case, future kilometer-square size experiments may confirm such a scenario, or even the Super-Kamiokande results already put constraints on some dark matter models.
In a wino LSP scenario the annihilation cross section of winos gravitationally bound in galaxies can be boosted by a Sommerfeld enhancement factor which arises due to the ladder of exchanged W bosons between the initial states. The boost factor obtained can be in the range S ~ 10^4 if the mass is close to the resonance value of M ~ 4 TeV. In this paper we show that if one takes into account the Sommerfeld enhancement in the relic abundance calculation then the correct relic density is obtained for 4 TeV wino mass due to the enhanced annihilation after their kinetic decoupling. At the same time…
The PAMELA satellite has observed an excess in the positron to electron ratio above theoretical predictions in the range 10 - 100 GeV that increases with energy. We propose that the excess is not due to a change in the local interstellar spectrum, but is due to heliospheric modulation. We motivate this from the known form of the heliospheric magnetic field and predict that the excess will disappear when we enter a period of solar maximum activity.
Unexpected features in the energy spectra of cosmic rays electrons and positrons have been recently observed by PAMELA and Fermi-LAT satellite experiments, opening to the exciting possibility of an indirect manifestation of new physics. A TeV-scale fourth lepton family is a natural extension of the Standard Model leptonic sector (also linked to the hierarchy problem in Minimal Walking Technicolor models). The heavy Majorana neutrino of this setup mixes with Standard Model charged leptons through a weak charged current interaction. Here, we first study analytically the energy spectrum of the el…
We demonstrate that an economical two Higgs doublet model can explain the electron and positron excesses in the recent ATIC and PAMELA experiments by the three body decays of the dark matter (DM) fermions without requiring the fine turning of the couplings and degeneracy of masses. We also show that the mass and lifetime of the decaying DM particle may not be fixed to be around 1 TeV and 10^{26} sec, respectively. Moreover, we note that this model includes a stable dark matter candidate as well.
Satellite data is accumulating that suggests and constrains dark matter physics. We argue there is a very well motivated theoretical preexisting framework consistent with dark matter annihilation being observed by the PAMELA satellite detector. The dark matter is (mainly) the neutral W boson superpartner, the wino with mass below 200 GeV. Using the program GALPROP we study the annihilation products and backgrounds together. Antimatter and gammas from annihilating winos contribute below this energy. We explain why PAMELA data does not imply no antiproton signal was observed by PAMELA or earlier…
The PAMELA positron excess is analyzed within the framework of nonuniversal SUGRA models with an extended $U(1)^n$ gauge symmetry in the hidden sector leading to neutralino dark matter with either a mixed Higgsino-wino LSP or an essentially pure wino dominated LSP. The Higgsino-wino LSP can produce the observed PAMELA positron excess and satisfy relic density constraints in the extended class of models due to a near degeneracy of the mass spectrum of the extended neutralino sector with the LSP mass. The simultaneous satisfaction of the WMAP relic density data and the PAMELA data is accomplishe…
