Abstract
We study gravitino dark matter and slow gravitino decays within the framework of R-violating supersymmetry, with particular emphasis on the flavour dependence of the branching ratios and the allowed R-violating couplings. The dominant decay modes and final state products turn out to be very sensitive to the R-violating hierarchies. Mixing effects can be crucial in correctly deriving the relative magnitude of the various contributions, particularly for heavy flavours with phase space suppression. The study of the strength of different decay rates for the gravitino is also correlated to collider signatures expected from decays of the Next-to-Lightest Supersymmetric Particle (NLSP) and to single superparticle production.
Highlights
There has been renewed interest in the possibility of having gravitino dark matter within the framework of R-violating supersymmetry [1, 2], which occurs if the gravitino decays are slow enough for its lifetime to be larger than the age of the universe [3, 4]
Depending on the flavour of the R-violating operator, the nature of the Next-to-Lightest Supersymmetric Particle (NLSP), and the respective λmax that we found in the previous section, one would generically expect either: (i) possible observable single superparticle productions, if λ can be sufficiently large [5, 6, 31], (ii) Minimal Supersymmetric Standard Model (MSSM) production of sparticle pairs followed by R-violating decays of the NLSP, for the flavours where λmax is smaller than ∼ 10−2, or (iii) no R-violatig decays of the NLSP inside detectors for very small λmax, with some cross-over region where displaced vertices could be observed
(ii) if the NLSP is a neutralino with a mass larger than the top, it should have a rapid three-body decay with a top in the final state, on the other hand, if the neutralino is lighter than the top, it should decay via either subdominant operators or mixing effects, which may well enhance its decay rate enough for it to decay within the detector, giving a displaced vertex
Summary
There has been renewed interest in the possibility of having gravitino dark matter within the framework of R-violating supersymmetry [1, 2], which occurs if the gravitino decays are slow enough for its lifetime to be larger than the age of the universe [3, 4] This is an exciting possibility that allows supersymmetric dark matter, even if the symmetries of the fundamental theory result in an unstable Lightest Supersymmetric Particle (LSP) [5,6,7].
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