CCFM prediction for F_2 and forward jets at HERA

TL;DR

This work applies the CCFM evolution equation to predict the inclusive structure function $F_2$ and forward-jet production at HERA energies, using a modified SMALLX Monte Carlo that includes the non-Sudakov factor and the consistency constraint. The study shows that with appropriate parameter choices and a scale for alpha_s tied to $k_t^2$, the model describes $F_2$ over the $x$ and $Q^2$ ranges and reproduces forward-jet data; it highlights the importance of the $1/(1-z)$ contributions and the impact of the consistency constraint on the cross-section. The results indicate that CCFM can capture forward-jet phenomena, bridging BFKL-like dynamics and DGLAP evolution through angular ordering and unintegrated gluon distributions. These findings support the use of CCFM-based Monte Carlo tools for modeling small-$x$ QCD effects at colliders.

Abstract

Predictions of the CCFM evolution equation for F_2 and forward jets at HERA energies are obtained from a modified version of the Monte Carlo program SMALLX. The treatment of the non-Sudakov form factor $Δ_{ns}$ is discussed as well as the effect of the so called "consistency constraint". For the first time a good description of F_2 and the forward jet data is obtained from the CCFM equation.

Figures (2)

• Figure 1: The structure function $F_2(x,Q^2)$ compared to H1 data H1_F2_1996. The solid (dashed) line is the prediction of the Monte Carlo without (with) applying the "consistency constraint" (c.c.) and the dotted line includes only the $1/(1-z)$ term.
• Figure 2: The cross section for forward jet production as a function of $x$, compared to H1 data H1_fjets_data ($a.$) and compared to ZEUS data ZEUS_fjets_data ($b.$). The solid (dashed) line is the prediction of the Monte Carlo without (with) applying the "consistency constraint" (c.c.) and the dotted line includes only the $1/(1-z)$ term.