Twist Decomposition of Proton Structure from BFKL and BK Amplitudes

An analysis of twist composition of Balitsky--Kovchegov (BK) amplitude is performed in the double logarithmic limit. In this limit, the BK evolution of color dipole--proton scattering is equivalent to BFKL evolution which follows from vanishing of the Bartels vertex in the collinear limit. We perform twist decomposition of the BFKL/BK amplitude for proton structure functions and find compact analytic expressions that provide accurate approximations for higher twist amplitudes. The BFKL/BK higher twist amplitudes are much smaller than those following from eikonal saturation models