Baryogenesis with Superheavy Squarks

We consider a setup where R-parity is violated in the framework of split supersymmetry. The out-of-equilibrium decays of heavy squarks successfully lead to the generation of a baryon asymmetry. We restrict the R-parity violating couplings to the baryon number violating subset to keep the neutralino sufficiently stable to provide the dark matter. The observed baryon asymmetry can be generated for squark masses larger than 10^11 GeV, while neutralino dark matter induces a stronger bound of 10^13 GeV. Some mass splitting between left- and right-handed squarks may be needed to satisfy also constraints from gluino cosmology.Comment: 18 pages, LaTeX, 4 figure

Supersymmetric Thermalization and Quasi-Thermal Universe: Consequences for Gravitinos and Leptogenesis

Motivated by our earlier paper \cite{am}, we discuss how the infamous gravitino problem has a natural built in solution within supersymmetry. Supersymmetry allows a large number of flat directions made up of {\it gauge invariant} combinations of squarks and sleptons. Out of many at least {\it one} generically obtains a large vacuum expectation value during inflation. Gauge bosons and Gauginos then obtain large masses by virtue of the Higgs mechanism. This makes the rate of thermalization after the end of inflation very small and as a result the Universe enters a {\it quasi-thermal phase} after the inflaton has completely decayed. A full thermal equilibrium is generically established much later on when the flat direction expectation value has substantially decareased. This results in low reheat temperatures, i.e., $T_{\rm R}\sim {\cal O}({\rm TeV})$, which are compatible with the stringent bounds arising from the big bang nucleosynthesis. There are two very important implications: the production of gravitinos and generation of a baryonic asymmetry via leptogenesis during the quasi-thermal phase. In both the cases the abundances depend not only on an effective temperature of the quasi-thermal phase (which could be higher, i.e., $T\gg T_{\rm R}$), but also on the state of equilibrium in the reheat plasma. We show that there is no ``thermal gravitino problem'' at all within supersymmetry and we stress on a need of a new paradigm based on a ``quasi-thermal leptogenesis'', because in the bulk of the parameter space the {\it old} thermal leptogenesis cannot account for the observed baryon asymmetry.Comment: 53 pages. Final version published in JCA

Supermassive gravitinos, dark matter, leptogenesis, and flat direction baryogenesis

In general the gravitino mass and/or the soft supersymmetry breaking masses in the observable sector can be much larger than the TeV scale. Depending on the relation between the masses, new important channels for gravitino production in the early Universe can arise. Gravitinos with a mass above 50 TeV decay before big bang nucleosynthesis, which leads to relaxation of the well known bound on the reheating temperature $T_{\rm R} \leq 10^{10}$ GeV. However, if the heavy gravitinos are produced abundantly in the early Universe, their decay can alter the abundance of the lightest supersymmetric particle. Moreover, they may dominate the energy density of the Universe. Their decay will in this case increase entropy and dilute already created baryon asymmetry and dark matter. Such considerations put new constraints on gravitino and sfermion masses, and the reheating temperature. In this paper we examine various cosmological consequences of supermassive gravitinos. We discuss advnatges and disadvantages of a large reheating temperature in connection with thermal leptogenesis, and find that large parts of the parameter space are opened up for the lightest right-handed (s)neutrino mass. We also discuss the viability of Affleck-Dine baryogenesis under the constraints from gravitino decay, and gravitino production from the decay of Q-balls