$Λ_b \to Λ$ Form Factors from Light-Cone Sum Rules with $Λ$-Baryon Distribution Amplitudes

We compute the $Λ_b \to Λ$ transition form factors using light-cone sum rules based on $Λ$-baryon distribution amplitudes, including contributions up to twist--6. The analysis is performed for pseudoscalar, vector, and axial-vector $b\to s$ currents and for different choices of the $Λ_b$ interpolating current. We find that only the pseudoscalar interpolating current leads to numerically stable and phenomenologically viable form factors. The resulting form factors are parametrised using a $z$-expansion and applied to the rare decay $Λ_b \to Λ\ell^+ \ell^-$, yielding predictions for branching ratios in the low-$q^2$ region.

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