We consider the proton decay in supersymmetric models with a gravitino or axino lighter than the proton. This consideration leads to a stringent limit on the R parity and B violating Yukawa coupling of the superpotential operator U^c_i D^c_j D^c_k as $\lambda"_{ 112} < 10^{ -15} (m_{ 3/2}/eV)$ for a light gravitino, and $\lambda"_{ 112} < 10^{ -15} (F_a/ 10^{ 10} GeV)$ for a light DFSZ axino. For hadronic axino, the constraint is weakened by the factor of 10^{ 3}.
Categories: hep-ph