The MSSM from Scherk-Schwarz Supersymmetry Breaking

Abstract

We present a five-dimensional model compactified on an interval where supersymmetry is broken by the Scherk-Schwarz mechanism. The gauge sector propagates in the bulk, two Higgs hypermultiplets are quasilocalized, and quark and lepton multiplets localized, in one of the boundaries. The effective four-dimensional theory is the MSSM with very heavy gauginos, heavy squarks and light sleptons and Higgsinos. The soft tree-level squared masses of the Higgs sector can be negative and they can (partially) cancel the positive one-loop contributions from the gauge sector. Electroweak symmetry breaking can then comfortably be triggered by two-loop radiative corrections from the top-stop sector. The fine tuning required to obtain the electroweak scale is found to be much smaller than in the MSSM, with essentially no fine-tuning for few TeV gaugino masses. All bounds from direct Higgs searches at LEP and from electroweak precision observables can be satisfied. The lightest supersymmetric particle is a (Higgsino-like) neutralino that can accomodate the abundance of Dark Matter consistently with recent WMAP observations.