Abstract
We present a novel mechanism of supersymmetry breaking embeddable in string theory and simultaneously sharing the main advantages of (sequestered) gravity and gauge mediation. It is driven by a Scherk–Schwarz deformation along a compact extra dimension, transverse to a brane stack supporting the supersymmetric extension of the Standard Model. This fixes the magnitude of the gravitino mass, together with that of the gauginos of a bulk gauge group, at a scale as high as 10^{10} GeV. Supersymmetry breaking is mediated to the observable sector dominantly by gauge interactions using massive messengers transforming non-trivially under the bulk and Standard Model gauge groups and leading to a neutralino LSP as dark matter candidate. The Higgsino mass mu and soft Higgs-bilinear B_mu term could be generated at the same order of magnitude as the other soft terms by effective supergravity couplings as in the Giudice–Masiero mechanism.
Highlights
The main motivation for gauge-mediated supersymmetry breaking is that it provides flavor independent soft breaking terms avoiding strong experimental constraints on flavor changing neutral currents (FCNC). It has some problematic drawbacks: (i) One loses the standard dark matter candidate as a WIMP since the lightest supersymmetric particle (LSP) is the gravitino; (ii) The gravitino can be dark matter only if its mass is m3/2 1 keV, which requires an upper bound on the messenger mass, M, over its number, N, as M/N 107 GeV, while for larger gravitino masses the reheating temperature after inflation is strongly constrained; (iii) There is no compelling way to generate a supersymmetric μ-parameter (Higgsino mass) and a Bμ soft term (Higgs bilinear) of the same order as the other soft terms
We presented a novel mechanism of supersymmetry breaking where the Standard Model (SM) gaugino, squark, and slepton masses arise predominantly from flavor blind gaugemediated interactions, while the gravitino mass is superheavy due to an appropriate sequestering of the supersymmetry breaking sector
We have presented an example for how μ and Bμ parameters could be generated at the same time by effective supergravity interactions, as in the Giudice– Masiero mechanism
Summary
The main motivation for gauge-mediated supersymmetry breaking (see for example [3] and references therein) is that it provides flavor independent soft breaking terms avoiding strong experimental constraints on flavor changing neutral currents (FCNC). It has some problematic drawbacks: (i) One loses the standard dark matter candidate as a WIMP (weakly interacting massive particle) since the LSP is the gravitino; (ii) The gravitino can be (warm) dark matter only if its mass is m3/2 1 keV, which requires an upper bound on the messenger mass, M, over its number, N , as M/N 107 GeV, while for larger gravitino masses the reheating temperature after inflation is strongly constrained; (iii) There is no compelling way to generate a supersymmetric μ-parameter (Higgsino mass) and a Bμ soft term (Higgs bilinear) of the same order as the other soft terms None of these problems can disqualify gauge mediation as a very appealing mechanism of supersymmetry breaking transmission to the observable sector it would be certainly interesting to find a theory where these problems do not appear. Gravity mediation effects from the hidden to the observable sector are exponentially suppressed by the branes separation In all these models gravity is sequestered from the gauge interactions of gauge mediation, a heavy enough gravitino with a mass range 100 GeV–100 TeV is obtained and the LSP, and Dark Matter candidate, is the lightest neutralino. In Appendix A, we present the details of the computation of the induced F-auxiliary expectation value in the messenger sector off-shell, needed for the evaluation of the gauge-mediated contributions in the main text
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