Constraining dark matter properties with gamma-rays from the Galactic Center with Fermi-LAT

We study the capabilities of the Fermi-LAT instrument on board of the Fermi mission to constrain particle dark matter properties, as annihilation cross section, mass and branching ratio into dominant annihilation channels, with gamma-ray observations from the Galactic Center. Besides the prompt gamma-ray flux, we also take into account the contribution from the electrons/positrons produced in dark matter annihilations to the gamma-ray signal via inverse Compton scattering off the interstellar photon background, which turns out to be crucial in the case of dark matter annihilations into μ⁺μ⁻ and e⁺e⁻ pairs. We study the signal dependence on different parameters like the region of observation, the density profile, the assumptions for the dark matter model and the uncertainties in the propagation model. We also show the effect of the inclusion of a 20% systematic uncertainty in the gamma-ray background. If Fermi-LAT is able to distinguish a possible dark matter signal from the large gamma-ray background, we show that for dark matter masses below ∼200 GeV, Fermi-LAT will likely be able to determine dark matter properties with good accuracy.     

Nonlinear increase in the energy input into a medium at the fusion of regularized femtosecond filaments

We consider dark matter consisting of long-living particles with masses 10⁷ GeV ? M ?10¹⁶ GeV decaying through hadronic channel as a source of high-energy neutrino. Using recent data on high-energy neutrino from IceCube and Pierre Auger experiments, we derive the upper-limits on neutrino flux from dark matter decay and constraints on dark matter parameter space. For the dark matter masses of order 10⁸ GeV the constraints derived are slightly stronger than those obtained for the same dark matter model using the highenergy gamma-ray limits.     

Cosmic Gamma-ray from inverse Compton process in unstable dark matter scenario

Motivated by the PAMELA anomaly in the fluxes of cosmic-ray e⁺$e^{+}$ and e⁻$e^{-}$, we study the cosmic γ  -ray induced by the inverse Compton (IC) scattering process in unstable dark matter scenario assuming that the anomaly is due to the e^±$e^{\pm }$ emission by the decay of dark matter. We calculate the fluxes of IC-induced γ-ray produced in our Galaxy and that from cosmological distance, and show that both of them are significant. If the γ-ray flux is precisely determined by Fermi Gamma-ray Space Telescope for various line-of-sight directions, it will provide an important test of the decaying dark matter scenario.     

Low-scale neutrino seesaw mechanism and scalar dark matter

Recently the AMS-02 experiment has released the data of positron fraction with a very small statistical error. Because of the small error, it is no longer easy to fit the data with single dark matter for a fixed diffusion model and dark matter profile. In this paper, we propose a new interpretation of the data: that it originates from decay of two-component dark matter. This interpretation gives a rough threshold of the lighter DM component. When DM decays into leptons, the positron fraction in the cosmic rays depends on the flavor of the final states, and this is fixed by imposing a non-Abelian discrete symmetry on our model. By assuming two gauge-singlet fermionic decaying DM particles, we show that a model with non-Abelian discrete flavor symmetry, e.g. $T_{13}$ , can give a much better fitting to the AMS-02 data compared with a single-component dark matter scenario. Few dimension-six operators of the universal leptonic decay of DM particles are allowed in our model, since its decay operators are constrained by the $T_{13}$ symmetry. We also show that the lepton masses and mixings are consistent with current experimental data, due to the flavor symmetry.     

Yangian algebra in the bi-qubit system and mixed light pseudoscalar meson state

We extend the holographic Ricci dark energy model to include some direct, non-gravitational interaction between dark energy and dark matter. We consider three phenomenological forms for the interaction term Q in the model, namely, Q is taken proportional to the Hubble expansion rate and the energy densities of dark sectors (taken to be ?? _de, ?? _m, and ?? _de+?? _m, respectively). We obtain a uniform analytical solution to the three interacting models. Furthermore, we constrain the models by using the latest observational data, including the 557 Union2 type Ia supernovae data, the cosmic microwave background anisotropy data from the 7-yr WMAP, and the baryon acoustic oscillation data from the SDSS. We show that in the interacting models of the holographic Ricci dark energy, a more reasonable value of ?? _m0 will be obtained, and the observations favor a rather strong coupling between dark energy and dark matter.     

Non-perturbative effect on thermal relic abundance of dark matter

We point out that thermal relic abundance of the dark matter is strongly altered by a non-perturbative effect called the Sommerfeld enhancement, when constituent particles of the dark matter are non-singlet under the SU(2)_L gauge interaction and much heavier than the weak gauge bosons. Typical candidates for such dark matter particles are the heavy wino- and higgsino-like neutralinos. We investigate the non-perturbative effect on the relic abundance of dark matter for the wino-like neutralino as an example. We show that its thermal abundance is reduced by 50% compared to the perturbative result. The wino-like neutralino mass consistent with the observed dark matter abundance turns out to be 2.7 TeV?m?3.0 TeV$2.7\text{TeV}?m?3.0\text{TeV}$.     

Explanations of the DAMPE high energy electron/positron spectrum in the dark matter annihilation and pulsar scenarios

Many studies have shown that either the nearby astrophysical source or dark matter(DM)annihilation/decay can be used to explain the excess of high energy cosmic ray(CR)e~±,which is detected by many experiments,such as PAMELA and AMS-02.Recently,the dark matter particle explorer(DAMPE)collaboration has reported its first result of the total CR e~±spectrum from 25 Ge V to 4.6 Te V with high precision.In this work,we study the DM annihilation and pulsar interpretations of this result.We show that the leptonic DM annihilation channels toτ~+τ~-,4μ,4τ,and mixed charged lepton final states can well explain the DAMPE e~±spectrum.We also find that the mixed charged leptons channel would lead to a sharp drop structure at～Te V.However,the ordinary DM explanations have been almost excluded by the constraints from the observations of gamma-ray and CMB,unless some exotic DM models are introduced.In the pulsar scenario,we analyze 21 nearby known pulsars and assume that one of them dominantly contributes to the high energy CR e~±spectrum.Involving the constraint from the Fermi-LAT observation of the e~±anisotropy,we find that two pulsars could explain the DAMPE e~±spectrum.Our results show that it is difficult to discriminate between the DM annihilation and single pulsar explanations of high energy e~±with the current DAMPE result.     

Non-thermal dark matter,high energy cosmic rays and late-decaying particles from inflationary quantum fluctuations

It has been suggested that the origin of cosmic rays above the GZK limit might be explained by the decay of particles, X, with mass of the order of 10¹² GeV. Generation of heavy particles from inflationary quantum fluctuations is a prime candidate for the origin of the decaying X particles. It has also been suggested that the problem of non-singular galactic halos might be explained if dark matter originates non-thermally from the decay of particles, Y, such that there is a free-streaming length of the order of 0.1 Mpc. Here we explore the possibility that quantum fluctuations might account for the Y particles as well as the X particles. For the case of non-thermal WIMP dark matter with unsuppressed weak interactions we find that there is a general problem with deuterium photo-dissociation, disfavouring WIMP dark matter candidates. For the case of more general dark matter particles, which may have little or no interaction with conventional matter, we discuss the conditions under which X and Y scalars or fermions can account for non-thermal dark matter and cosmic rays. For the case where X and Y scalars are simultaneously produced, we show that galactic halos are likely to have a dynamically significant component of X scalar cold dark matter in addition to the dominant non-thermal dark matter component.     

Interpretation of the DAMPE 1.4 TeV peak according to the decaying dark matter model

Highly accurate measurements of cosmic ray electron flux by the dark matter particle explorer(DAMPE) ranging between 25 Ge V and 4.6 Te V have recently been published. A sharp peak structure was found at ～ 1.4 Te V. This unexpected peak structure can be reproduced by the annihilation/decay of a nearby dark matter(DM) halo. In this study, we adopt the decaying-DM model to interpret the ～ 1.4 Te V peak. We found that the decay products of the local DM subhalo could contribute to the DMAPE peak with mDM= 3 Te V and τ～ 10~(28) s. We also obtain constraints on DM lifetime and the distance of the local DM subhalo by comparison with DAMPE data.     

Cosmic-ray antiproton constraints on light singlino-like dark matter candidates

The CoGeNT experiment, dedicated to direct detection of dark matter, has recently released excess events that could be interpreted as elastic collisions of ∼10 GeV dark matter particles, which might simultaneously explain the still mysterious DAMA/LIBRA modulation signals, while in conflict with results from other experiments such as CDMS, XENON-100 and SIMPLE. It was shown that 5-15 GeV singlino-like dark matter candidates arising in singlet extensions of minimal supersymmetric scenarios can fit these data; annihilation then mostly proceeds into light singlet-dominated Higgs (pseudo-)scalar fields. We develop an effective Lagrangian approach to confront these models with the existing data on cosmic-ray antiprotons, including the latest PAMELA data. Focusing on a parameter space consistent with the CoGeNT region, we show that the predicted antiproton flux is generically in tension with the data whenever the produced (pseudo-)scalars can decay into quarks energetic enough to produce antiprotons, provided the annihilation S-wave is significant at freeze out in the early universe. In this regime, a bound on the singlino annihilation cross section is obtained, 〈σv〉?¹⁰−26 cm³/s, assuming a dynamically constrained halo density profile with a local value of ρ_⊙=0.4 GeV/cm³. Finally, we provide indications on how PAMELA or AMS-02 could further constrain or detect those configurations producing antiprotons which are not yet excluded.     

Cosmological Constraints on Polytropic Gas Model

We study the polytropic gas scenario as the unification of dark matter and dark energy. We fit the model parameters by using the latest observational data including type Ia supernovae, baryon acoustic oscillation, cosmic microwave background, and Hubble parameter data. At 68.3 % and 95.4 % confidence levels, we find the best fit values of the model parameters as $\tilde{K}=0.742_{-0.024}^{+0.024}(1\sigma)_{-0.049}^{+0.048}(2\sigma)$ and $n=-1.05_{-0.08}^{+0.08}(1\sigma)_{-0.16}^{+0.15}(2\sigma)$ . Using the best fit values of the model, we obtain the evolutionary behaviors of the equation of state parameters of the polytropic gas model and dark energy, the deceleration parameter of the universe, the dimensionless density parameters of dark matter and dark energy as well as the growth factor of structure formation. Then, we investigate different energy conditions in the polytropic gas model and obtain that only the strong energy condition is violated for the special ranges of the redshift. We also conclude that in the this model, the universe starts from the matter dominated epoch and approaches a de Sitter phase at late times, as expected. Further, the universe begins to accelerate at redshift z _t=0.74. Furthermore, in contrary to the ΛCDM model, the cosmic coincidence problem is solved naturally in the polytropic gas scenario. Moreover, this model fits the data of the growth factor well as the ΛCDM model.     

Dynamical interactions of dark energy and dark matter:Yang-Mills condensate and QCD axions

We analyze a model of cold axion dark matter weakly coupled with a dark gluon condensate,reproducing dark energy.We first review how to recover the dark energy behavior using the functional renormalization group approach,and ground our study in the properties of the effective Lagrangian,to be determined non-perturbatively.Then,within the context of G_(SM)×SU(2)_D×U(1)_(P Q),we consider Yang-Mills condensate(YMC)interactions with QCD axions.We predict a transfer of dark energy density into dark matter density,that can be tested in the next generation of experiments dedicated to dark energy measurements.We obtain new bounds on the interactions between the Yang-Mills condensate and axion dark matter from Planck data:the new physics interaction scale related to the axion/gluon condensate mixing is constrained to be higher than the 10~6GeV energy scale.     

PAMELA and dark matter

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, and find that they do not. We then perform a general analysis of annihilations into two-body states to determine what weighted combination of channels best describes the data.     

Interference of Nonstandard Interactions with Standard Model in $${B^0} \to {\pi ^0}\bar vv$$, $$B_c^ - \to {D^ - }\bar vv$$Bc−→D−v¯v and $$\bar B_s^0 \to {K^0}\bar vv$$B¯s0→K0v¯v Decays

We study the contributions of nonstandard neutrino interactions (NSI) to the rare decays of pseudoscalar mesons involving neutrinos in the final state \({B^0} \to {\pi ^0}\bar vv\), \(B_c^ - \to {D^ - }\bar vv\) and \(\bar B_s^0 \to {\bar K^0}\bar vv\), It is pointed that dominant contribution comes from the interference between standard model and nonstandard interaction We predict limits on NSIs free parameter ε ^uL _ττ and compare them with experimental data. We further compare our results with perturbative QCD (pQCD) and QCD results for these reactions.     

Constraints on the MSSM from the Higgs sector

We discuss the constraints on supersymmetry in the Higgs sector arising from LHC searches, rare B decays and dark matter direct detection experiments. We show that constraints derived on the mass of the lightest h ⁰ and the CP-odd A ⁰ bosons from these searches are covering a larger fraction of the SUSY parameter space compared to searches for strongly interacting supersymmetric particle partners. We discuss the implications of a mass determination for the lightest Higgs boson in the range 123<M _h <127?GeV, inspired by the intriguing hints reported by the ATLAS and CMS Collaborations, as well as those of a non-observation of the lightest Higgs boson for MSSM scenarios not excluded at the end of 2012 by LHC and direct dark matter searches and their implications on LHC SUSY searches.     

Asymmetric dark matter from hidden sector baryogenesis

We consider the production of asymmetric dark matter during hidden sector baryogenesis. We consider a particular supersymmetric model where the dark matter candidate has a number density approximately equal to the baryon number density, with a mass of the same scale as the b, c and τ. Both baryon asymmetry and dark matter are created at the same time in this model. We describe collider and direct detection signatures of this model.     

Significant gamma lines from inert Higgs dark matter

One way to unambiguously confirm the existence of particle dark matter and determine its mass would be to detect its annihilation into monochromatic gamma-rays in upcoming telescopes. One of the most minimal models for dark matter is the inert doublet model, obtained by adding another Higgs doublet with no direct coupling to fermions. For a mass between 40 and 80 GeV, the lightest of the new inert Higgs particles can give the correct cosmic abundance of cold dark matter in agreement with current observations. We show that for this scalar dark matter candidate, the annihilation signal of monochromatic gammagamma and Zgamma final states would be exceptionally strong. The energy range and rates for these gamma-ray line signals make them ideal to search for with the soon upcoming GLAST satellite.     

Cosmic-ray positron from superparticle dark matter and the PAMELA anomaly

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.