We explore here a new mechanism by which the out of equilibrium decay of heavy gravitinos , followed by possible R-parity violating decays in the Minimal Supersymmetric Standard Model ( MSSM ) can generate the baryon asymmetry of the universe .
In this mechanism , gravitino decay produces a CP-asymmetry that is carried by squarks or sleptons .
These particles then decay through R-parity violating operators generating a lepton asymmetry .
The lepton asymmetry is converted into a baryon asymmetry by weak sphalerons , as in the familiar case of leptogenesis by Majorana neutrino decays .
To ensure that the gravitino decays while the sphaleron is still in equilibrium , we obtain a lower bound on the gravitino mass , m _ { 3 / 2 } \gtrsim 10 ^ { 8 } \mathrm { GeV } , and therefore our mechanism requires a high scale of SUSY breaking , as well as minimum reheating temperature after inflation of T \gtrsim 10 ^ { 12 } \mathrm { GeV } in order to for the gravitino density to be sufficiently large to generate the baryon asymmetry today .
We consider each of the MSSM ’ s relevant R-parity violating operators in turn , and derive constraints on parameters in order to give rise to a baryon asymmetry comparable to that observed today , consistent with low energy phenomenological bounds on SUSY models .