* Astronomy

Title: Neutrino Signals from Annihilating/Decaying Dark Matter in the Light of Recent Measurements of Cosmic Ray Electron/Positron Fluxes
Authors: Junji Hisano, Masahiro Kawasaki, Kazunori Kohri, Kazunori Nakayama
(Version v3)

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 kilometre-square size experiments may confirm such a scenario, or even the Super-Kamiokande results already put constraints on some dark matter models.

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Title: PAMELA/ATIC anomaly from the meta-stable extra dark matter component and the leptophilic Yukawa interaction
Authors: Bumseok Kyae

We present a supersymmetric model with two dark matter (DM) components explaining the galactic positron excess observed by PAMELA/HEAT and ATIC/PPB-BETS: One is the conventional lightest supersymmetric particle (LSP) \chi, and the other is a TeV scale meta-stable neutral singlet N_D, which is a Dirac fermion (N,N^c). In this model, N_D decays dominantly into \chi e^+e^- through an R parity preserving dimension 6 operator with the life time \tau_N ~ 10^{26} sec. We introduce a pair of vector-like superheavy SU(2) lepton doublets (L,L^c) and lepton singlets (E,E^c). The dimension 6 operator leading to the N_D decay is generated from the leptophilic Yukawa interactions by W \supset Ne^cE+L^ch_uE+Lh_de^c with the dimensionless couplings of order unity, and a gauge interaction by {\cal L} \supset g'\tilde{e}^{c*}e^c\chi + h.c. The superheavy masses of the vector-like leptons (~ 10^{16} GeV) are responsible for the longevity of N_D. The low energy field spectrum in this model is just the MSSM fields and N_D. Even for the case that the portion of N_D is much smaller than that of \chi in the total DM density [{\cal O}(10^{-10}) \lesssim n_D/n_\chi], the observed positron excess can be explained with a relatively light mass of E and E^c (10^{11} GeV \lesssim M_E \lesssim 10^{16} GeV). The smallness of the electron mass is also explained in this framework. This model is easily embedded in the flipped SU(5) grand unification, which is a leptophilic unified theory.

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Title: White dwarf axions, PAMELA data, and flipped-SU(5)
Authors: Kyu Jung Bae, Ji-Haeng Huh, Jihn E. Kim, Bumseok Kyae, Raoul D. Viollier
(Version v2)

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)_\Gamma]_{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)_\Gamma and two component cold dark matters from Z_2 parity. We show that in the flipped-SU(5) there exists a basic mechanism for allowing excess positrons through the charged SU(2) singlet leptons, but not allowing anti-proton excess due to the absence of the SU(2) singlet quarks. We show the discovery potential of the charged SU(2) singlet E at the LHC experiments by observing the electron and positron spectrum. With these symmetries, we also comment on the mass hierarchy between the top and bottom quarks.

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Title: Dissecting Pamela (and ATIC) with Occam's Razor: existing, well-known Pulsars naturally account for the "anomalous" Cosmic-Ray Electron and Positron Data
Authors: Stefano Profumo (University of California, Santa Cruz)

We argue that both the positron fraction measured by PAMELA and the peculiar spectral features reported in the total differential electron-positron flux measured by ATIC have a very natural explanation in electron-positron pairs produced by nearby pulsars. We show that the greatly improved quality of current data allow us to reverse-engineer the problem: given the regions of pulsar parameter space favoured by PAMELA and by ATIC, are there known pulsars that naturally explain the data? We address this question by (1) outlining simple theoretical models for estimating the energy output, the diffusion setup and the injection spectral index of electron-positron pairs, and by (2) considering all known pulsars (as given in the ATNF catalogue). It appears unlikely that a single pulsar be responsible for both the PAMELA result and for the ATIC excess, although two sources are enough to naturally explain both of the experimental results. We list several candidate pulsars that can individually or coherently contribute to explain the PAMELA and ATIC data. We point out that Fermi-LAT will play a decisive role in the very near future, by (1) providing us with an exquisite measurement of the electron-positron flux that will make it possible to distinguish between various pulsar scenarios, and by (2) unveiling the existence of as yet undetected gamma-ray pulsars that can significantly contribute to the local electron-positron flux.

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