${\mathrm{\Lambda }}_b\to \mathrm{\Lambda }$ Form Factors from Light-Cone Sum Rules with $\mathrm{\Lambda }$-Baryon Distribution Amplitudes

We compute the ${\mathrm{\Lambda }}_b\to \mathrm{\Lambda }$ transition form factors using light-cone sum rules based on $\mathrm{\Lambda }$-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 ${\mathrm{\Lambda }}_b$ 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 ${\mathrm{\Lambda }}_b\to \mathrm{\Lambda }{\mathrm{\ell }}^{+}{\mathrm{\ell }}^{-}$, yielding predictions for branching ratios in the low-$q^2$ region.