Measurement of the diffractive structure function $F_2^{D(3)}$

TL;DR

This paper presents measurements of the diffractive structure function $F_2^{D(3)}$ across various kinematic regions, comparing results with QCD and Regge models, and exploring the role of higher twist effects and BFKL dynamics.

Contribution

It provides new experimental data on $F_2^{D(3)}$ in previously unexplored kinematic regions and compares these with theoretical models, including QCD, Regge phenomenology, and BFKL dynamics.

Findings

Diffractive trajectory has an intercept larger than soft hadronic data.

Higher twist contributions are significant at large $eta$ and low $Q^2$.

Data are consistent with models based on two-gluon exchange and BFKL dynamics.

Abstract

Measurements of the diffractive structure function $F_2^{D(3)}(x_{\PO}, \beta, Q^2)$, describing the process $ep \to eXY$, are presented in the two kinematic regions $0.4 \leq Q^2 \leq 5$, ${\rm GeV}^2$, $0.001 \leq \beta \leq 0.65$, and $200 \leq \beta \leq 800 {\rm GeV^2}$, $0.4 \leq \beta \leq 0.9$, both with $\xpom < 0.05$, $M_{_Y} < 1.6 {\rm GeV}$ and $|t| < 1.0 {\rm GeV^2}$. Together with published measurements at intermediate $Q^2$, the data are compared with models based on QCD and Regge phenomenology. The diffractive trajectory is found to have an intercept larger than that describing soft hadronic data and consistent with that determined using previously published H1 measurements at intermediate $Q^2$ alone. The data are also parameterised using a QCD motivated model based on the exchange of two gluons from the proton. In this model, the higher twist contribution to $F_2^{D(3)}$ at large $\beta$ is found to be important at low $Q^2$. The data are also compared with models based on BFKL dynamics.