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Title Large extra dimensions
Author Βεμόγιαννης, Γεώργιος
Thesis advisor Τσάμης, Νικόλαος
Abstract According to the Large Extra Dimensions (LED) model of Arkani-Hamed,Dimopoulos, and Dvali (ADD), in addition to the (3+1) observed space-time dimensions, there exists n gravity-only spatial dimensions. Due to the presence of the additional dimensions, the Planck scale of gravity should be brought down from 1016 TeV to the T eV scale, near the electroweak scale, and thus solve the hierarchy problem. Based on the ADD theory, Kaluza-Klein (KK) gravitons, having masses of the order 100MeV and lifetimes of the order of billions of years, are expected to be produced within supernovae cores by nucleon-nucleon gravi-bremsstrahlung in the LED model. Once produced, they are predicted to be trapped by the gravitational potential of subsequently formed neutron stars(NS), and their decay is predicted to contribute to a measurable gamma-ray flux from NS. In the first part, the model of Large Extra Dimensions is presented, as well as the graviton emission process that the ADD model predicts. Furthermore the theory behind the emission of KK Gravitons by Nucleon-Nucleon Bremsstrahlung is shown, as well as differential fluxes (from KK Graviton Decay) for various sources. Lastly other proposed theories of extra dimensions are briefly shown. In the second part, experimental constraints are portrayed. More explicitly, this section starts with previous experimental constraints setted on Newtonian inverse square law and the Yukawa parametrization, collider constraints (TeVatron, LHC), and astrophysical constraints. In addition, analysed data from LHC Run 2 (2015 & 2016) are presented from the ATLAS and CMS Collaborations, which set lower limits on the minimum black hole masses, the ADD and RS1 models predicts, and on the ADD model parameter MD.
Language English
Issue date 2021-07-28
Collection   School/Department--School of Sciences and Engineering--Department of Physics--Graduate theses
  Type of Work--Graduate theses
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