EPJ

2023 Impact factor 4.2
EPJ C - Particles and Fields
Particles and Fields
Eur. Phys. J. C 9, 229-234
DOI 10.1007/s100529900066

Irreducible QCD backgrounds to top searches in semi-leptonic final states at the Next Linear Collider

S. Moretti

Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX, UK (e-mail: moretti@v2.rl.ac.uk)

Received: 12 January 1999 / Revised version: 24 March 1999 / Published online: 20 May 1999

Abstract
At future electron-positron colliders, one of the largest irreducible backgrounds to top searches in the channel `4 jets + lepton + missing energy' comes from QCD events of order $\alpha_s^2$. We compute here such processes exactly at the parton level by resorting to 2 $\rightarrow$ 6 matrix elements exploiting helicity amplitude techniques. We adopt a typical selection procedure based on the tagging of a high momentum and separated lepton. We finally outline kinematic differences between signal and background events that can be exploited to further reduce such a QCD noise.

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