Estimate of jet activity in tt̅ events

We present a calculation of jet activity associated with pair production of top quarks at hadron colliders and supercolliders. Our approach is based upon a merger of 2 → 3 matrix elements with initial and final state parton showers. We tabulate expected multijet rates in tt̅ events, and compare with O(α_s³) matrix element results and parton showers based upon 2 → 2 subprocesses. The merged calculation includes the correct matrix element for the first leg of the parton shower, but also includes the effects of approximate all-orders quark and gluon emission. We also evaluate expected jet activity in top pair events at hadron supercolliders; in particular, a comparison of the jet activity in the far forward region is made. It is found that the merged calculation yields more jet activity in the forward region than pure matrix element estimates, and also more jet activity in the central region. This can be important for background calculations to H→WW and strong WW scattering processes.