Phenomenological Aspects of Heterotic Effective Models At One Loop

We provide a study of the phenomenology of orbifold compactifications of the heterotic string within the context of supergravity effective theories. Our investigation focuses on those models where the soft Lagrangian is dominated by loop contributions to the various soft supersymmetry breaking parameters. We consider the pattern of masses that are governed by these soft terms and investigate the implications of certain indirect constraints on supersymmetric models, such as flavor-changing neutral currents, the anomalous magnetic moment of the muon and the density of thermal relic neutralinos.Comment: 5 pages, 2 figures, To appear in the proceedings of 2nd International Conference on String Phenomenology 2003, Durham, England, 29 Jul - 4 Aug 200

Signals from Galactic Center and Supergravity Models

We analyse the effect of the compression of the dark matter due to the infall of baryons to the galactic center on the gamma-ray flux. In addition, we also consider the effect of non-universal supersymmetric soft terms. This analysis shows that neutralino dark matter annihilation can give rise to signals largely reachable by future experiments like GLAST. This is a remarkable result if we realise that direct detection experiments will only be able to cover a small region of the parameter space. We have also studied the recent HESS data implying a neutralino heavier than 12 TeV. Because of such a heavy neutralino, it is not natural to find solutions in the SUGRA framework. Nevertheless we have carried out a quite model-independent analysis, and found the conditions required on the particle physics side to fit the HESS data thanks to dark matter annihilation.Comment: 6 pages, 3 figures, contributed to 41st Rencontres de Moriond on Electroweak Interactions and Unified Theories, La Thuile, Aosta Valley, Italy, 11-18 Mar 200

Astroparticle and Collider Physics as complementary sources for the study of string motivated supergravity models

We provide a study of the phenomenology of heterotic orbifold compactifications scenarii within the context of supergravity effective theories. Our investigation focuses on those models where the soft Lagrangian is dominated by loop contributions to the various soft supersymmetry breaking parameters, giving a mixed anomaly-gravity mediation model. We consider the pattern of masses that are governed by these soft terms and investigate the implications of certain indirect constraints on supersymmetric models. In this framework, we point out how the complementarity between direct and indirect detection of a neutralino Dark Matter, and futur accelerator prospects can reduce considerably the parameter space of such modelsComment: 4 pages, 1 figure, to appear in the proceedings of International Conference on Linear Colliders (LCWS 05), Stanford, USA, 18-22 Mar 200

γ−\gamma-ray line generated by the Green-Schwarz mechanism

We study the phenomenology of a $U_X(1)$ extension of the Standard Model where the SM particles are not charged under the new abelian group. The Green-Schwarz mechanism insures that the model is anomaly free. The erstwhile invisible dark gauge field $X$, even if produced with difficulty at the LHC has however a clear signature in gamma-ray telescopes. We investigate what BSM scale (which can be interpreted as a low-energy string scale) would be reachable by the FERMI/GLAST telescope after 5 years of running and show that a 1 TeV scale can be testable, which is highly competitive with the LHC.Comment: Proceedings of DSU09 "The Dark Side of the Universe", 1-5 June 2009, Melbourne, 6 pages, 2 figure

Chargino and Neutralino Decays Revisited

We perform a comprehensive analysis of the decays of charginos and neutralinos in the Minimal Supersymmetric Standard Model where the neutralino $\chi_1^0$ is assumed to be the lightest supersymmetric particle. We focus, in particular, on the three-body decays of the next-to-lightest neutralino and the lightest chargino into the lightest neutralino and fermion-antifermion pairs and include vector boson, Higgs boson and sfermion exchange diagrams, where in the latter contribution the full mixing in the third generation is included. The radiative corrections to the heavy fermion and SUSY particle masses will be also taken into account. We present complete analytical formulae for the Dalitz densities and the integrated partial decay widths in the massless fermion case, as well as the expressions of the differential decay widths including the masses of the final fermions and the polarization of the decaying charginos and neutralinos. We then discuss these decay modes, in particular in scenarios where the parameter $\tan \beta$ is large and in models without universal gaugino masses at the Grand Unification scale where some new decay channels, such as decays into gluinos and $q\bar{q}$ pairs, open up.Comment: 51 pages with 13 figures, latex; uses axodraw.sty and epsfig.st

When LEP and Tevatron combined with WMAP and XENON100 shed light on the nature of Dark Matter

Recently, several astrophysical data or would-be signals has been observed in different dark-matter oriented experiments. In each case, one could fit the data at the price of specific nature of the coupling between the Standard Model (SM) particles and a light Dark Matter candidate: hadrophobic (INTEGRAL, PAMELA) or leptophobic (WMAP Haze, dijet anomalies of CDF, FERMI Galactic Center observation). In this work, we show that when one takes into account the more recent LEP and Tevatron analysis, a light thermal fermionic Dark Matte (\lesssim 10 GeV) that couples to electrons is mainly ruled out if one combines the analysis with WMAP constraints. We also study the special case of scalar dark matter, using a mono-photon events simulation to constrain the coupling of dark matter to electron.Comment: 8 pages, 6 figure