• Physique/Physique des Hautes Energies - Phénoménologie
  
• Mathématiques
  
• Planète et Univers/Astrophysique
  
• Physique/Astrophysique
  
• Physique/Relativité Générale et Cosmologie Quantique
  
• Physique/Physique des Hautes Energies - Théorie
  
• Physique/Physique des Hautes Energies - Expérience
  

Supersymmetric extensions of the standard model of particle physics assumingthe gravitino to be the lightest supersymmetric particle (LSP), and with thenext-to-LSP decaying to the gravitino during Big Bang nucleosynthesis, areanalyzed. Particular emphasis is laid on their potential to solve the "Li7problem", an apparent factor 2-4 overproduction of Li7 in standard Big Bangnucleosynthesis (BBN), their production of cosmologically important amounts ofLi6, as well as the resulting minimum gravitino dark matter densities in thesemodels. The study includes several improvements compared to prior studies.Heavy gravitinos in the constrained minimal supersymmetric standard model(CMMSM) are reanalyzed, whereas light gravitinos in gauge-mediatedsupersymmetry breaking scenarios (GMSB) are studied for the first time. It isconfirmed that decays of NLSP staus to heavy gravitinos, while producing allthe dark matter, may at the same time resolve the Li7 problem. For NLSP decaytimes ~ 1000 sec, such scenarios also lead to cosmologically important Li6 (andpossibly Be9) abundances. However, as such scenarios require heavy > 1 TeVstaus they are likely not testable at the LHC. It is found that decays of NLSPstaus to light gravitinos may lead to significant Li6 (and Be9) abundances,whereas NLSP neutralinos decaying into light gravitinos may solve the Li7problem. Though both scenarios are testable at the LHC they may not lead to theproduction of the bulk of the dark matter. A section of the paper outlinesparticle properties required to significantly reduce the Li7 abundance, and/orenhance the Li6 (and possibly Be9) abundances, by the decay of an arbitraryrelic particle.

We study the complementarity between the indirect detection of dark matter with gamma-rays in H.E.S.S. and the supersymmetry searches with ATLAS at the Large Hadron Collider in the Focus Point region within the mSUGRA framework. The sensitivity of the central telescope of the H.E.S.S. II experiment with an energy threshold of ~ 20 GeV is investigated. We show that the detection of gamma-ray fluxes of O(10^-12) cm-2s-1 with H.E.S.S. II covers a substantial part of the Focus Point region which may be more difficult for LHC experiments. Despite the presence of multi-TeV scalars, we show that LHC will be sensitive to a complementary part of this region through three body NLSP leptonic decays. This interesting complementarity between H.E.S.S. II and LHC searches is further highlighted in terms of the gluino mass and the two lightest neutralino mass difference.

The detection of non-baryonic dark matter through its gamma-ray annihilation in the centre of our galaxy has been studied. The gamma fluxes according to different models have been simulated and compared to those expected to be observed with the Alpha Magnetic Spectrometer (AMS), during a long-term mission on board of the International Space Station. Under the assumption that the dark matter halo is composed of the lightest, stable supersymmetric particle, the neutralino, the results of the simulations in the framework of mSUGRA models, show that with a cuspy dark matter halo or a clumpy halo, the annihilation gamma-ray signal would be detected by AMS. More optimistic perspectives are obtained with the Anomaly Mediated Supersymmetry Breaking (AMSB) model. The latter leads also to a cosmologically important 6Li abundance. Finally, the discovery potential for the massive Kaluza-Klein dark matter candidates has been evaluated and their detection looks feasible.