Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 1Citation - Scopus: 1Type-3/2 Seesaw Mechanism(American Physical Society, 2021) Demir, Durmuş Ali; Sargın, Ozan; Sargın, Ozan; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of TechnologyThe type-I seesaw mechanism provides a natural explanation for tiny neutrino masses. The right-handed neutrino masses it requires are, however, too large to keep the Higgs boson mass at its measured value. We show that vector spinors, singlet leptons that are like right-handed neutrinos, generate tiny neutrino masses naturally through the exchange of spin-1/2 and spin-3/2 components. This one-step seesaw mechanism, which we call the type-3/2 seesaw, keeps the Higgs boson mass unchanged at one loop and gives cause therefore to no fine-tuning problem. If the on-shell vector spinor is a pure spin-3/2 particle, then it becomes a potential candidate for hidden dark matter which gets diluted due only to the expansion of the Universe. The type-3/2 seesaw provides a natural framework for the neutrino, Higgs boson, and dark matter sectors, with overall agreement with current experiments and observations.Article Citation - WoS: 134Citation - Scopus: 161Search for New Physics in Final States With an Energetic Jet or a Hadronically Decaying W or Z Boson and Transverse Momentum Imbalance at $\sqrt{s} = $ 13 Tev(American Physical Society, 2018) CMS Collaboration; Karapınar, Güler; Karapınar, Güler; 01. Izmir Institute of TechnologyA search for new physics using events containing an imbalance in transverse momentum and one or more energetic jets arising from initial-state radiation or the hadronic decay of W or Z bosons is presented. A data sample of proton-proton collisions at s=13 TeV, collected with the CMS detector at the LHC and corresponding to an integrated luminosity of 35.9 fb-1, is used. The observed data are found to be in agreement with the expectation from standard model processes. The results are interpreted as limits on the dark matter production cross section in simplified models with vector, axial-vector, scalar, and pseudoscalar mediators. Interpretations in the context of fermion portal and nonthermal dark matter models are also provided. In addition, the results are interpreted in terms of invisible decays of the Higgs boson and set stringent limits on the fundamental Planck scale in the Arkani-Hamed, Dimopoulos, and Dvali model with large extra spatial dimensions.Article Citation - WoS: 22Citation - Scopus: 27Search for Dark Matter and Supersymmetry With a Compressed Mass Spectrum in the Vector Boson Fusion Topology in Proton-Proton Collisions at ?s =8 Tev(American Physical Society, 2017) CMS Collaboration; Karapınar, Güler; 01. Izmir Institute of TechnologyA first search for pair production of dark matter candidates through vector boson fusion in proton-proton collisions at s=8 TeV is performed with the CMS detector. The vector boson fusion topology enhances missing transverse momentum, providing a way to probe supersymmetry, even in the case of a compressed mass spectrum. The data sample corresponds to an integrated luminosity of 18.5 fb-1, recorded by the CMS experiment. The observed dijet mass spectrum is consistent with the standard model expectation. In an effective field theory, dark matter masses are explored as a function of contact interaction strength. The most stringent limit on bottom squark production with mass below 315 GeV is also reported, assuming a 5 GeV mass difference with respect to the lightest neutralino.Article Citation - WoS: 14Citation - Scopus: 32Search for Dark Matter and Unparticles Produced in Association With a Z Boson in Proton-Proton Collisions at Sqrt(s) =8 Tev(American Physical Society, 2016) CMS Collaboration; Karapınar, Güler; 01. Izmir Institute of TechnologyA search for evidence of particle dark matter (DM) and unparticle production at the LHC has been performed using events containing two charged leptons, consistent with the decay of a Z boson, and large missing transverse momentum. This study is based on data collected with the CMS detector corresponding to an integrated luminosity of 19.7 fb-1 of pp collisions at the LHC at a center-of-mass energy of 8 TeV. No significant excess of events is observed above the number expected from the standard model contributions. The results are interpreted in terms of 90% confidence level limits on the DM-nucleon scattering cross section, as a function of the DM particle mass, for both spin-dependent and spin-independent scenarios. Limits are set on the effective cutoff scale Λ, and on the annihilation rate for DM particles, assuming that their branching fraction to quarks is 100%. Additionally, the most stringent 95% confidence level limits to date on the unparticle model parameters are obtained.Article Citation - WoS: 24Citation - Scopus: 25Sneutrino Dark Matter: Symmetry Protection and Cosmic Ray Anomalies(American Physical Society, 2010) Demir, Durmuş Ali; Demir, Durmuş Ali; Frank, Mariana; Selbuz, Levent; Turan, İsmail; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of TechnologyWe 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: 10Citation - Scopus: 12Neutralino Dark Matter in the Left-Right Supersymmetric Model(American Physical Society, 2006) Demir, Durmuş Ali; Demir, Durmuş Ali; Turan, İsmail; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of TechnologyWe 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: 78Citation - Scopus: 79Minimal U(1)' Extension of the Minimal Supersymmetric Standard Model(American Physical Society, 2005) Demir, Durmuş Ali; Demir, Durmuş Ali; Wang, Ting T.; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of TechnologyMotivated 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.