69,862 research outputs found

    Anomalous internal pair conversion signaling elusive light neutral particles

    Get PDF
    In this paper we report on a systematic search for a neutral boson in the mass range between 5 and 15 MeV/c2^{2} in the decay of highly excited nuclei. Its signature is found a deviation in the angular correlation of the e+e−e^+e^- pairs from conventional internal pair conversion (IPC) resulting from of its two-body decay kinematics. With an e+e−e^{+}e^{-} pair-spectrometer, a number of transitions has been investigated in the α{\alpha}--nuclei 8^{8}Be, 12^{12}C and 16^{16}O, following light ion induced reactions at low bombarding energies, first at IKF in Frankfurt and during the last years at ATOMKI in Debrecen. Startlingly, in all isoscalar transitions excess e+e−e^{+}e^{-} pairs are found at large angles with branching ratios with respect to the total yield ranging from 10−2^{-2} to 10−6^{-6}. If these deviations are all related to the two-body decay of an XX-boson, this observation implies plural XX-bosons. An analysis of all angular spectra with a boson search program, yields a pandemonium of more than ten candidate bosons.Comment: 7 pages, 2 figures, contributed paper to the Int. Symposium on Exotic Nuclear Systems (ENS05), ATOMKI, Debrecen, Hungary, 20-25 June 200

    The Discovery of the Higgs Boson with the CMS Detector and its Implications for Supersymmetry and Cosmology

    Full text link
    The discovery of the long awaited Higgs boson is described using data from the CMS detector at the LHC. In the SM the masses of fermions and the heavy gauge bosons are generated by the interactions with the Higgs field, so all couplings are related to the observed masses. Indeed, all observed couplings are consistent with the predictions from the Higgs mechanism, both to vector bosons and fermions implying that masses are indeed consistent of being generated by the interactions with the Higgs field. However, on a cosmological scale the mass of the universe seems not to be related to the Higgs field: the baryonic mass originates from the binding energy of the quarks inside the nuclei and dark matter is not even predicted in the SM, so the origin of its mass is unknown. The dominant energy component in the universe, the dark energy, yields an accelerated expansion of the universe, so its repulsive gravity most likely originates from a kind of vacuum energy. The Higgs field would be the prime candidate for this, if the energy density would not be many orders of magnitude too high, as will be calculated. The Higgs mass is found to be 125.7±\pm0.3(stat.)±\pm0.3(syst.) GeV, which is below 130 GeV, i.e. in the range predicted by supersymmetry. This may be the strongest hint for supersymmetry in spite of the fact that the predicted supersymmetric particles have not been discovered so far.Comment: 26 pages, Conference Proceedings Time and Matter (TAM2013), Venice, Feb. 201

    First record of a white rough-toothed dolphin (Steno bredanensis) off West Africa including notes on rough-toothed dolphin surface behaviour

    Get PDF
    In June 2009, a white rough-toothed dolphin (Steno bredanensis) calf was photographed in a group of at least 50 dolphins in the southern Gulf of Guinea, 95 nauticol miles off the Gabon coast (01°45'S 007°29'E), West Africa. Reports of unusually pigmented cetaceans are infrequent and this record represents the first of an all-white rough-toothed dolphin. Furthermore, there is little documentation concerning rough-toothed dolphins and this note contributes to the knowledge of this species in tropical West African water

    Perspectives on the detection of supersymmetric Dark Matter

    Full text link
    Up to now searches for Dark Matter (DM) detection have not been successful, either because our paradigm in how DM signals should look like are wrong or the detector sensitivity is still too low in spite of the large progress made in recent years. We discuss both possibilities starting with what we know about DM from cosmology and why Supersymmetry provides such an interesting paradigm for cosmology and particle physics in order to appreciate what it means to give up this paradigm. In addition, we compare the predicted cross sections for direct and indirect DM detection with observations with emphasis on the latest developments. Especially, we discuss the possible origins of the two hotly debated candidates for a DM annihilation signal, namely the positron excess and the Fermi GeV excess, which are unfortunately incompatible with each other and more mundane astrophysical explanations exist.Comment: 18 pages, 12 figures. Invited talk at ICNFP2017, August 2017, Crete, Greec

    A new Determination of the Extragalactic Background of Diffuse Gamma Rays taking into account Dark Matter Annihilation

    Full text link
    The extragalactic background (EGB) of diffuse gamma rays can be determined by subtracting the Galactic contribution from the data. This requires a Galactic model (GM) and we include for the first time the contribution of dark matter annihilation (DMA), which was previously proposed as an explanation for the EGRET excess of diffuse Galactic gamma rays above 1 GeV. In this paper it is shown that the newly determined EGB shows a characteristic high energy bump on top of a steeply falling soft contribution. The bump is shown to be compatible with a contribution from an extragalactic DMA signal from weakly interacting massive particles (WIMPs) with a mass between 50 and 100 GeV in agreement with the EGRET excess of the Galactic diffuse gamma rays and in disagreement with earlier analysis. The remaining soft contribution of the EGB is shown to resemble the spectra of the observed point sources in our Galaxy.Comment: 7 pages, 4 figures. Accepted by A&A, made Fig. 4 and table 1 consisten

    Indirect Dark Matter Searches in the Light of ATIC, FERMI, EGRET and PAMELA

    Full text link
    Recently, new data on antiprotons and positrons from PAMELA, e- + e+ spectra from ATIC, FERMI and HESS up to TeV energies all indicate deviations from expectations, which has caused an interesting mix of new explanations, ranging from background, standard astrophysical sources to signals from dark matter (DM) annihilation. Unfortunately, the excess in positrons is not matched with obvious excesses in antiprotons or gamma rays, so a new class of DM scenarios with leptophilic WIMP candidates have been invoked. On the other hand, the increase in the positron fraction, which could have had any spectral shape for new physics, matches well the shape expected from proton background.Comment: Invited talk at SUSY09, the 17th International Conference on Supersymmetry and the Unification of Fundamental Interactions, Boston, 200
    • …
    corecore