The Azimuthal Decorrelation of Jets Widely Separated in Rapidity

Abstract

This study reports the first measurement of the azimuthal decorrelation between jets with pseudorapidity separation up to five units. The data were accumulated using the DØdetector during the 1992--1993 collider run of the Fermilab Tevatron at $\sqrt{s}=$ 1.8 TeV. These results are compared to next--to--leading order (NLO) QCD predictions and to two leading--log approximations (LLA) where the leading--log terms are resummed to all orders in $α_{\scriptscriptstyle S}$. The final state jets as predicted by NLO QCD show less azimuthal decorrelation than the data. The parton showering LLA Monte Carlo {\small HERWIG} describes the data well; an analytical LLA prediction based on BFKL resummation shows more decorrelation than the data.

Figures (4)

• Figure 1: Typical event topology in multijet events.
• Figure 2: The pseudorapidity interval, $\Delta\eta = |\eta_{1} - \eta_{2}|$, of the two jets at the extremes of pseudorapidity. The coverage extends to $\Delta\eta \sim 6$. The errors are statistical only.
• Figure 3: The azimuthal angle difference, $\Delta\phi = \phi_{1} - \phi_{2}$, distribution of the two jets at the extremes of pseudorapidity plotted as $1 - \Delta\phi/\pi$ for $\Delta\eta=1$, 3, and 5 ($0.5 < \Delta\eta < 1.5$, $2.5 < \Delta\eta < 3.5$, and $4.5 < \Delta\eta < 5.5$). The errors are statistical only.
• Figure 4: The correlation variable used in this analysis, the average value of $\cos (\pi-\Delta\phi)$ vs. $\Delta\eta$, for the data, JETRAD, HERWIG, and the BFKL calculations of Del Duca and Schmidt.