Thrust jet analysis of deep-inelastic large-rapidity-gap events

Abstract. A thrust analysis of Large-Rapidity-Gap events in deep-inelastic $$ep$$ collisions is presented, using data taken with the H1 detector at HERA in 1994. The average thrust of the final states $$X$$, which emerge from the dissociation of virtual photons in the range \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document} $10 < Q^2 < 100 {\rm GeV}^2$\end{document}, grows with hadronic mass $$M_X$$ and implies a dominant 2-jet topology. Thrust is found to decrease with growing $$P_t$$, the thrust jet momentum transverse to the photon-proton collision axis. Distributions of $$P_t^2$$ are consistent with being independent of $$M_X$$. They show a strong alignment of the thrust axis with the photon-proton collision axis, and have a large high$$-P_t$$ tail. The correlation of thrust with $$M_X$$ is similar to that in $$e^+e^-$$annihilation at $$\sqrt s_{ee}=M_X$$, but with lower values of thrust in the $$ep$$ data. The data cannot be described by interpreting the dissociated system $$X$$ as a $$q\bar q$$ state but inclusion of a substantial fraction of $$q\bar q g$$ parton configurations leads naturally to the observed properties. The soft colour exchange interaction model does not describe the data.