Physics / Fizik

Permanent URI for this collectionhttps://hdl.handle.net/11147/6

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  • Article
    Citation - WoS: 24
    Citation - Scopus: 25
    Sneutrino Dark Matter: Symmetry Protection and Cosmic Ray Anomalies
    (American Physical Society, 2010) Demir, Durmuş Ali; Everett, Lisa L.; Frank, Mariana; Selbuz, Levent; Turan, İsmail
    We present an R-parity conserving model of sneutrino dark matter within a Higgsphilic U(1)′ extension of the minimal supersymmetric standard model. In this theory, the μ parameter and light Dirac neutrino masses are generated naturally upon the breaking of the U(1)′ gauge symmetry. One of the right-handed sneutrinos is the lightest supersymmetric particle. The leptonic and hadronic decays of another sneutrino, taken to be the next-to-lightest superpartner, allow for a natural fit to the recent results reported by the PAMELA experiment. We perform a detailed calculation of the dark matter relic density in this scenario, and show that the model is consistent with the ATIC and Fermi LAT experiments. © 2010 The American Physical Society.
  • Article
    Citation - WoS: 10
    Citation - Scopus: 12
    Neutralino Dark Matter in the Left-Right Supersymmetric Model
    (American Physical Society, 2006) Demir, Durmuş Ali; Frank, Mariana; Turan, İsmail
    We study the neutralino sector of the left-right supersymmetric model. In addition to the possibilities available in the minimal supersymmetric model, the neutralino states can be superpartners of the U(1)B-L gauge boson, the neutral SU(2)R gauge boson, or of the Higgs triplets. We analyze neutralino masses and determine the parameter regions for which the lightest neutralino can be one of the new pure states. We then calculate the relic density of the dark matter for each of these states and impose the constraints coming from the ρ parameter, the anomalous magnetic moment of the muon, b→sγ, as well as general supersymmetric mass bounds. The lightest neutralino can be the bino, or the right-wino, or the neutral triplet Higgsino, all of which have different couplings to the standard model particles from the usual neutralinos. A light bino satisfies all the experimental constraints and would be the preferred dark matter candidate for light supersymmetric scalar masses, while the right-wino would be favored by intermediate supersymmetric mass scales. The neutral triplet Higgs fermion satisfies the experimental bounds only in a small region of the parameter space, for intermediate to heavy supersymmetric scalar masses.
  • Article
    Citation - WoS: 78
    Citation - Scopus: 79
    Minimal U(1)' Extension of the Minimal Supersymmetric Standard Model
    (American Physical Society, 2005) Demir, Durmuş Ali; Kane, Gordon L.; Wang, Ting T.
    Motivated by the apparent need for extending the minimal supersymmetric standard model (MSSM) and perhaps mitigating naturalness problems associated with the μ parameter and fine-tuning of the soft masses, we augment the MSSM spectrum by a SM gauge singlet chiral superfield, and enlarge the gauge structure by an additional U(1)′ invariance, so that the gauge and Higgs sectors are relatively secluded. One crucial aspect of U(1)′ models is the existence of anomalies, the cancellation of which may require the inclusion of exotic matter which in turn disrupts the unification of the gauge couplings. In this work we pursue the question of canceling the anomalies with a minimal matter spectrum and no exotics. This can indeed be realized provided that U(1)′ charges are family dependent and the soft-breaking sector includes nonholomorphic operators for generating the fermion masses. We provide the most general solutions for U(1)′ charges by taking into account all constraints from gauge invariance and anomaly cancellation. We analyze various laboratory and astrophysical bounds ranging from fermion masses to relic density, for an illustrative set of parameters. The U(1)′ charges admit patterns of values for which family nonuniversality resides solely in the lepton sector, though this does not generate leptonic flavor-changing neutral currents due to the U(1)′ gauge invariance.