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\end{tabular} |
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\caption{ |
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Interpretation of the results of the search in (a) the same-sign dilepton final state for |
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bottom squark pair production with $\tilde{b}\to t\chip$ depicted in Fig.~\ref{fig:diagrams}(d), and (b) |
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bottom squark pair production with $\tilde{b}\to t\chim$ depicted in Fig.~\ref{fig:diagrams}(d), and (b) |
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the all-hadronic final state for bottom squark pair production with $\tilde{b}\to b\lsp$ depicted in Fig.~\ref{fig:diagrams}(c). |
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\label{fig:ss_interpretation} |
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} |
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\end{figure*} |
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|
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This section presents a search in the same-sign (SS) dilepton final state, based on 10.5 fb$^{-1}$. |
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A wide variety of new physics processes may produce events with SS leptons, which provide a very clean |
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A wide variety of new physics scenarios may produce events with SS leptons, which provide a very clean |
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final state due to low SM background expectations. In particular, this final state is sensitive to |
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direct pair production of bottom squarks with $\tilde{b}\to t \chi^{\pm}\to t W \lsp$ depicted in Fig.~\ref{fig:diagrams}(d), |
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direct pair production of bottom squarks with $\tilde{b}\to t \chim \to t W \lsp$ depicted in Fig.~\ref{fig:diagrams}(d), |
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as well as to gluino-mediated production of top and bottom squarks. |
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|
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We select events with two leptons (e or $\mu$) with \pt\ $>$ 20 GeV and dilepton invariant mass $m_{\ell\ell}>8$ GeV. |
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leptons in jet events. The second background, estimated from MC, consists of rare SM processes and is dominated |
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by $t\bar{t}$W and $t\bar{t}$Z. The systematic uncertainty on both the fake lepton and rare backgrounds is 50\%. |
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A third, small background contribution is from ``charge flips'' and consists of events with opposite-sign leptons |
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where one of the leptons is an electron whose charge is misreconstructed. This background is based on MC predictions, |
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which are validated using a sample of Z$\to e^+e^-$ events. |
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where one of the leptons is an electron whose charge is misreconstructed. |
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> |
This background is estimated using the electron charge misreconstruction probability, which is extracted from studies of Z$\to e^+e^-$ events in data. |
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> |
%This background is based on MC predictions, which are validated using a sample of Z$\to e^+e^-$ events. |
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|
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Signal regions are defined by placing additional requirements on the jet multiplicity, b-tagged jet multiplicity, |
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\met, and $H_T$, defined as the scalar sum of the transverse momenta of selected jets. |
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The observed data yields in all signal regions are in good agreement with the SM background expectations; |
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see Ref.~\cite{ref:ss} for the full quantitative results. The signal region that is most sensitive to |
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bottom squark pair production with $\tilde{b}\to t \chi^{\pm}$ depicted in Fig.~\ref{fig:diagrams}(d) |
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bottom squark pair production with $\tilde{b}\to t \chim$ depicted in Fig.~\ref{fig:diagrams}(d) |
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has at least four jets, \met\ $>$ 120 GeV and |
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$H_T$ $>$ 200 GeV. In this region we observe 1 event in data and predict 2.22 $\pm$ 0.96 events. |
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The results are used to exclude a region of the model parameter space in Fig.~\ref{fig:ss_interpretation}(a), |
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which demonstrates that our search probes bottom squarks with masses up to 450 GeV. |
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The constraint on the bottom squark from naturalness considerations is similar to that on the top squark, |
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suggesting a bottom squark with mass less than 500-700~GeV. |
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Naturalness considerations suggest a bottom squark with mass not exceeding 500--700 GeV, similar to the constraint |
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on the top squark mass. |
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Several additional interpretations for models with gluino-mediated top and |
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bottom squark production are presented in Ref.~\cite{ref:ss}. |
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|
