Improved Light-Cone QCD Sum Rule Analysis of Rare Decays Λb → Λγ and Λb → Λl+l-

We present a systematic light-cone QCD sum rule study of the exclusive rare radiative decay Lambda(b) -> Lambda gamma and rare semileptonic decay Lambda(b) -> Lambda l(+)l(-) within the framework of the standard model. Although some light-cone sum rule (LCSR) studies on these rare processes can be found in different literatures, it is necessary to reanalyze them systematically for the reason that either the baryonic distribution amplitudes are improved or different interpolating currents for the Lambda(b) baryon may lead to quite different results. In addition, the rare process Lambda(b) -> Lambda gamma has not yet been analyzed by LCSR with the Ioffe-type current. Taking all these reasons into account, we perform LCSR calculations of both the processes with two types of interpolating currents. Our calculations show that the choice of the interpolating current for the Lambda(b) baryon can affect the predictions significantly, especially for the rare radiative decay process.