Preselection

The preselection cuts are applied to remove background events that are obviously not ${\rm W}^{+}{\rm W}^{-}\rightarrow{\rm q}\bar{\rm q}\ell\bar{\nu}_{\ell}$ events, such as the two-photon events. It also removes a significant fraction of the ${\rm Z}^{0}/\gamma \rightarrow {\rm q}\bar{\rm q}$ events.

A number of cuts are applied to both the ${\rm W}^{+}{\rm W}^{-}\rightarrow{\rm q}\bar{\rm q}{\rm e}\bar{\nu}_{\rm e}$ and ${\rm W}^{+}{\rm W}^{-}\rightarrow{\rm q}\bar{\rm q}\mu\bar{\nu}_{\mu}$ selections, these are:

$\bullet$

E $_{\rm lepton} > 10$ GeV

$\bullet$

$\cos\theta_{\rm lpmis} < 0.9$

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${\rm P(e),P}(\mu) > 10^{-9}$

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$0.3 <{\rm R}_{\rm vis} < 1.2$

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N $_{\rm CT} > 5$

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R $_{\rm shw} > 0.1$

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N $_{\rm EC} > 7$

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E $_{\rm FD} < (\sqrt{s}- {\rm M}_{{\rm Z}^{0}} - 10 {\rm GeV})$

$\bullet$

E $_{\gamma}< (\sqrt{s}- {\rm M}_{{\rm Z}^{0}} - 10 {\rm GeV})$

In addition to these, the reconstructed $s^{\prime}$ is required to be greater than 60 GeV$^{2}$ for the ${\rm W}\rightarrow{\rm e}\bar{\nu}_{\rm e}$ and greater than 90 GeV for the ${\rm W}\rightarrow\mu\bar{\nu}_{\mu}$.

Further cuts are applied to the ${\rm W}^{+}{\rm W}^{-}\rightarrow{\rm q}\bar{\rm q}{\rm e}\bar{\nu}_{\rm e}$ selection designed to reduce the backgrounds from two-photon events, which can resemble ${\rm W}^{+}{\rm W}^{-}\rightarrow{\rm q}\bar{\rm q}{\rm e}\bar{\nu}_{\rm e}$ events and also further reduce the backgrounds from radiative ${\rm Z}^{0}/\gamma \rightarrow {\rm q}\bar{\rm q}$ events where the initial state photon converts into an electron-positron pair and one of the leptons is lost down the beam pipe. The cuts designed to reduce these backgrounds are:

$\bullet$

If E $_{\rm lepton}$ is within 12 GeV of $(\sqrt{s}-{\rm M}_{\rm Z^{0}})$ then the following are applied:

$\rightarrow$

Event is rejected if the track of the lepton candidate and an oppositely charged track appear to have originated from the conversion of a photon.

$\rightarrow$

$5<\frac{\rm dE}{\rm dx}<15$ ${\rm keV cm}^{-1}$.

$\rightarrow$

If $\frac{\rm dE}{\rm dx}$ is not well measured the event is rejected.

$\rightarrow$

If the electron candidates within 32$^{\circ}$of the beam-pipe then $\vert\vec{p}\vert > 10$ GeV.

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If the lepton candidate appears to have come from the conversion of a photon and the kinematic fit converged, then ${\rm P}(\sqrt{s}) < 0.01$.

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$\vert\cos\theta_{\rm mis}\vert < 0.975$. This cut is designed to reject events where a lepton passing down the beam pipe is mistaken as the missing momentum of a neutrino.