The ${\rm Z}^{0}/\gamma \rightarrow {\rm q}\bar{\rm q}$ Background

The ${\rm Z}^{0}/\gamma \rightarrow {\rm q}\bar{\rm q}$ processes are shown in figure 5.3. The final states produced by this process are generally unlike the signal process. However, if the initial state photon converts into an electron-positron pair and one of the leptons is lost down the beam pipe, the event could resemble a signal process. Furthermore, the photon is often radiated with an energy that means the ${\rm Z}^{0}$ is on-shell. This would mean that the jets would be boosted and also have a similar invariant mass to a W boson. As the ${\rm Z}^{0}/\gamma \rightarrow {\rm q}\bar{\rm q}$ process has a cross-section 13 times higher than that of the signal process it is a major contribution to the accepted background processes.

Figure: The ${\rm Z}^{0}/\gamma \rightarrow {\rm q}\bar{\rm q}$ background processes.