The process `e+ e- --> H t t-bar' and its backgrounds at future electron-positron colliders

TL;DR

This paper calculates the detailed background processes for Higgs production with top quarks at future electron-positron colliders, providing precise predictions to aid in measuring the Higgs-top coupling.

Contribution

It presents exact tree-level calculations of complex 2-to-8 processes including signal and backgrounds for Higgs-top studies at linear colliders.

Findings

Computed total rates and spectra for signal and background processes.

Analyzed the impact of backgrounds on Higgs-top coupling measurements.

Provided detailed helicity amplitude calculations for complex final states.

Abstract

The process $e^+e^-\to H t\bar t$ can be used at the Next Linear Collider to measure the Higgs-top Yukawa coupling. In this paper, we compute $2\to 8$ processes of the form $e^+e^-\to b\bar b b\bar b W^+W^-\to b\bar b b\bar b \ell^\pm\nu_\ell q\bar q'$, accounting for the Higgs-top-antitop signal as well as several irreducible backgrounds in the semi-leptonic top-antitop decay channel. We restrict ourselves to the case of a light Higgs boson in the range 100 GeV $\le M_H \le$ 140 GeV. We use helicity amplitude techniques to compute exactly such processes at tree level in the framework of the Standard Model. Total rates and differential spectra of phenomenological interest are given and discussed