H-->WW as the discovery mode for a light Higgs boson

Abstract

The production cross section for a m_H=115 GeV, SM Higgs boson in weak boson fusion at the LHC is sizable. However, the branching fraction for H-->WW is expected to be relatively small. The signal, with its two forward jets, is sufficiently different from the main backgrounds that a signal to background ratio of better than 1:1 can nevertheless be obtained, with large enough rate to allow for a 5 sigma signal with 35 fb^{-1} of data. The H-->WW signal in weak boson fusion may thus prove to be the discovery mode for the Higgs boson at the LHC.

Figures (4)

• Figure 1: Distribution of events in the $\Delta\phi(ll,=\hbox{$p$}p \hbox{/} _T)$ vs. $p_{TH}$ plane, where $\Delta\phi(ll,=\hbox{$p$}p \hbox{/} _T)$ is the azimuthal angle between the dilepton momentum and the missing transverse momentum. Event numbers correspond to 2000 fb$^{-1}$ and the cuts of Eqs. (\ref{['eq:basic']}--\ref{['eq:MTWW.cut']}) and include suppression factors from a central jet veto on extra parton radiation above $p_T=20$ GeV. The four panels represent a $m_H=115$ GeV signal, the combined $W^+W^-$ backgrounds from $WWjj$ and $t\bar{t}+$jets sources, the $bbjj$ background and the combined $\tau\tau jj$ backgrounds. Events below and to the left of the straight lines are eliminated by the contour cuts of Eq. (\ref{['eq:contour']}).
• Figure 2: Missing transverse momentum distribution, $d\sigma/d=\hbox{$p$}p \hbox{/} _T$, after the cuts of Eqs. (\ref{['eq:basic']}--\ref{['eq:contour']}) for $l^+l^-=\hbox{$p$}p \hbox{/} _T$ events. The areas between curves represent the contributions from the various background classes, as indicated, and the signal. QCD and EW backgrounds and the $t\bar{t}$ backgrounds have been combined for clarity. The $l^+l^-jj$ background is indicated by the dashed curve. The vertical line represents the cut of Eq. (\ref{['eq:cuts.ll']}).
• Figure 3: Distribution of the smallest invariant mass of a tagging-jet and a charged-lepton, after the cuts of Eqs. (\ref{['eq:basic']}--\ref{['eq:contour']}). The areas between curves represent the contributions from the various background classes, as indicated, and the signal. QCD and EW backgrounds and the $t\bar{t}$ backgrounds have been combined for clarity.
• Figure 4: $WW$ transverse mass distribution, $d\sigma/dM_T(WW)$, after the cuts of Eqs. (\ref{['eq:basic']}--\ref{['eq:contour']}) for $e\mu=\hbox{$p$}p \hbox{/} _T$ events. The areas between curves represent the contributions from the various background classes and the signal, as indicated. The $bbjj$ background is effectively eliminated by the cut of Eq. (\ref{['eq:emucut']}) with minimal effect on the signal or the other backgrounds.