Proton Decay in a 6D SO(10) model

We present a study of proton decay in a supersymmetric $SO(10)$ gauge theory in six dimensions compactified on an orbifold. The dimension 5 proton decay operators are absent, but the dimension 6 are enhanced due to the presence of KK towers. We resum the KK modes up to the cut-off of the theory and find the rate for the dominant mode $p \to \pi^0 e^{+}$. We explore also the flavour dependence, due to the different localization of states in the extra dimensions and find that it is possible to distinguish the model from the usual 4D $SU(5)/SO(10)$ models.Comment: Contribution to 40th Rencontres de Moriond on Electroweak Interactions and Unified Theories, La Thuile, Italy, 5-12 Mar 2005., LaTeX,6 pages,1 figur

What we can learn on inflation from recent CMBR data

We review the prediction of inflation and the constraints on inflationary models coming from recent observations.Comment: 10 pages, 2 figures; to be published in JHEP - Proceedings of the International Europhysics Conference on High Energy Physics, July 12-18, 2001,Budapest, Hungar

Minimal Decaying Dark Matter and the LHC

We consider a minimal Dark Matter model with just two additional states, a Dark Matter Majorana fermion and a colored or electroweakly charged scalar, without introducing any symmetry to stabilize the DM state. We identify the parameter region where an indirect DM signal would be within the reach of future observations and the DM relic density generated fits the observations. We find in this way two possible regions in the parameter space, corresponding to a FIMP/SuperWIMP or a WIMP DM. We point out the different collider signals of this scenario and how it will be possible to measure the different couplings in case of a combined detection.Comment: 33 pages, 13 figure

Gravitino Dark Matter and low-scale Baryogenesis

A very simple way to obtain comparable baryon and DM densities in the early Universe is through their contemporary production from the out-of-equilibrium decay of a mother particle, if both populations are suppressed by comparably small numbers, i.e. the CP violation in the decay and the branching fraction respectively. We present a detailed study of this kind of scenario in the context of a R-parity violating realization of the MSSM in which the baryon asymmetry and the gravitino Dark Matter are produced by the decay of a Bino. The implementation of this simple picture in a realistic particle framework results, however, quite involving, due to the non trivial determination of the abundance of the decaying Bino, as well as due to the impact of wash-out processes and of additional sources both for the baryon asymmetry and the DM relic density. In order to achieve a quantitative determination of the baryon and Dark Matter abundances, we have implemented and solved a system of coupled Boltzmann equations for the particle species involved in their generation, including all the relevant processes. In the most simple, but still general, limit, in which the processes determining the abundance and the decay rate of the Bino are mediated by degenerate right-handed squarks, the correct values of the DM and baryon relic densities are achieved for a Bino mass between 50 and 100 TeV, Gluino NLSP mass in the range 15-60 TeV and a gravitino mass between 100 GeV and few TeV. These high masses are unfortunately beyond the kinematical reach of LHC. On the contrary, an antiproton signal from the decays of the gravitino LSP might be within the sensitivity of AMS-02 and gamma-ray telescopes.Comment: 39 pages, 12 figure

Gamma-Rays from Decaying Dark Matter

We study the prospects for detecting gamma-rays from decaying Dark Matter (DM), focusing in particular on gravitino DM in R-parity breaking vacua. Given the substantially different angular distribution of the predicted gamma-ray signal with respect to the case of annihilating DM, and the relatively poor (of order 0.1$^\circ$) angular resolution of gamma-ray detectors, the best strategy for detection is in this case to look for an exotic contribution to the gamma-ray flux at high galactic latitudes, where the decaying DM contribution would resemble an astrophysical extra-galactic component, similar to the one inferred by EGRET observations. Upcoming experiments such as GLAST and AMS-02 may identify this exotic contribution and discriminate it from astrophysical sources, or place significant constraints on the mass and lifetime of DM particles.Comment: 15 pages, 5 figures, LaTeX with iopart.cls. Minor changes, typos corrected and references added/updated. Version accepted for publication in JCA

Effects of Squark Processes on the Axino CDM Abundance

We investigate the role of an effective dimension-4 axino-quark-squark coupling in the thermal processes producing stable cold axino relics in the early Universe. We find that, while the induced squark and quark scattering processes are always negligible, squark decays become important in the case of low reheat temperature and large gluino mass. The effect can tighten the bounds on the scenario from the requirement that cold dark matter axinos do not overclose the Universe.Comment: 20 pages, 9 figures, uses JHEP3.cl