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vimartin |
1.1 |
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In order to search for a possible signal from stop decays giving rise to a signature of \ttbar\ with additional \met\
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benhoob |
1.2 |
from the LSPs, it is necessary to determine the composition of the SM backgrounds in the signal region.
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| 4 |
vimartin |
1.1 |
This section details the methods pursued to estimate the background in the signal sample and describes the
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procedure to estimate the systematic uncertainties. The general strategy is to use the MC prediction for the
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backgrounds after applying corrections derived from data.
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The most important background to a stop signal arises from SM \ttbar. The \ttbar\ background may be
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separated into contributions containing a single lepton \ttlj\ and two leptons \ttll. As described in this section,
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the \ttll\ background is the dominant process satisfying the event selection, contributing $\sim 80\%$ of the
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| 11 |
benhoob |
1.2 |
signal sample defined with the benchmark selection of \met\ $>$ 100~\GeV and \mt\ $>$ 150~\GeV. This
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| 12 |
vimartin |
1.1 |
background has large true \met\ and consequently larger \mt\ due to the presence of two neutrinos.
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Additional contributions to the single lepton sample arise from \wjets\ and single top. The combination of
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all single lepton backgrounds, \ttlj, \wjets\ and single top, comprises $\sim 15\%$ of the signal sample.
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Finally, other background sources such as dibosons, \dy\ + jets, in addition to rarer processes such as \ttbar\
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produced in association with a vector boson and tribosons, provide a combined contribution to the signal sample
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at the level of $\sim 5\%$.
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| 18 |
benhoob |
1.2 |
Finally, the QCD background contribution is small, particularly in the signal sample, with a large \met\ requirement.
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| 19 |
vimartin |
1.1 |
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