Quantitative study of the transverse correlation of soft gluons in high energy QCD

Understand

We examine both analytically and numerically the validity of factorization for the double dipole scattering amplitude T^{(2)} which appears on the right hand side of the BK--JIMWLK equation.

• We demonstrate that, if one uses a dilute object (e.g., a proton in DIS) as the initial condition, the correlation in the transverse plane induced by the leading order BFKL evolution is generally strong, resulting in a violation of the mean field approximation T^{(2)} \approx TT even at zero impact parameter by a factor ranging from 1.5 to O(10) depending on the relative size of the scatterers and rapidity.
• This suggests that, within the experimentally accessible energy interval, the transverse correlation can significantly affect the nonlinear evolution of the dipole scattering amplitude.
• It also suggests that the nonlinear effects may set in earlier, already in the weak scattering regime.