; Lu, Cai-Dian] CAS, Inst High Energy Phys, Beijing 100049, Peoples R China
; [Wang, Yu-Ming
; Lu, Cai-Dian] CAS, Sci Facil, Ctr Theoret Phys, Beijing 100049, Peoples R China
; [Li, Ying] Yantai Univ, Dept Phys, Yantai 264005, Peoples R China
The weak decays of Lambda(b) -> Lambda + gamma and Lambda(b) -> Lambda + l(+)l(-) are investigated in the standard model using the light-cone sum-rule approach. The higher-twist distribution amplitudes of the Lambda baryon to the leading conformal spin are included in the sum rules for the transition form factors. Our results indicate that the higher-twist distribution amplitudes almost have no influence on the transition form factor f(2)(q(2)) defined by the tensor current, while such corrections can have a significant impact on the form factors g2(q(2)) defined by a vector current. Two phenomenological models (COZ and FZOZ) for the wave function of the. baryon are also employed in the sum rules for comparison, which can give rise to form factors approximately five times larger than that in terms of conformal expansion. Utilizing the form factors calculated in LCSR, the physical observables like the decay rate, the polarization asymmetry and forward-backward asymmetry are analyzed for the decays of Lambda(b) -> Lambda gamma, Lambda l(+)l(-).