to interact with a color neutral probe. One can usually order emissions in different variables, such as color, rapidity, transverse momentum and so on. Due to soft color coherence [@15] the ordering in rapidity and in color are equivalent however. This is used in the CCFM model where the initial state radiation is made up of gluons which are not followed, in rapidity, by a gluon with more energy, or equivalently positive light-cone momentum, $q_+ =q_0 + q_l$.

With the selection of the initial state radiation described above, it was shown by the authors that the unintegrated distribution function is given by $$\begin{aligned}
\mathcal{G}(x,k_{\perp}^2 , \bar{q} ) & \sim & \sum_{n} \prod_{i=1}^{n}
  \biggl[ \int \bar{\alpha }  \frac{dq_{\perp ,i}^2}{q_{\perp ,i}^2} \biggl(
  \frac{1}{z_i} \Delta _{ne} (z_i ,k_{\perp ,i}^2 ,\bar{q_i})+\frac{1}{1-z_i}
  \biggr) \Delta _S \times  \\
  & & \theta (\bar{q_i}-\bar{q}_{i-1}z_{i-1}) \biggr] \delta (x -
  \prod_{j}^{n} z_j ) \theta ( \bar{q}-\bar{q}_n z_n) \delta(k_{\perp}^2
  -k_{\perp n}^2)
\nonumber\end{aligned}$$ where $\bar{q}_i$ is defined by $\bar{q}_i \equiv q_{\perp ,i}/(1-z_i)$. $\Delta_{ne}$ stands for a non-eikonal form factor and $\Delta _S$ is the Sudakov form factor. They are given by $$\Delta _{ne}=\textrm{exp}
\biggl(-\bar{\alpha}\textrm{ln}\frac{1}{z}\textrm{ln}\frac{k_{\perp}}{z\bar{q}^2}\biggr);
\;\; \Delta _S =\textrm{exp} \biggl(-\bar{\alpha}\int \frac{dq_{\perp ,i}^2}{q_{\perp
    ,i}^2} \frac{dz}{1-z} \Theta _{order} \biggr)$$ Here $\Theta _{order}$ specifies the kinematic 