Perturbative QCD calculation for Λb→Λγ in the standard model

We calculate the branching ratio of Lambda(b)->Lambda gamma in the standard model using the PQCD method. The predicted branching ratio B(Lambda(b)->Lambda gamma) is about (4.3 similar to 8.6)x10(-8), with reasonable parameter ranges in the heavy baryon distribution amplitude. This branching ratio is much smaller than those obtained in other hadronic model calculations. Future experimental data can provide important information on applicability of the PQCD method to heavy baryon radiative decay.