| 6 |
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is an update of previous searches performed with 2011 data~\cite{ref:Zpaper,ref:EWKPAS}. |
| 7 |
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The search is based on a data sample of pp collisions collected at $\sqrt{s}=8$ TeV in 2012, |
| 8 |
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corresponding to an integrated luminosity of \lumi. |
| 9 |
+ |
{\bf For those readers interested in the ``edge analysis'' SUS-12-019, the relevant results may be found in App.~\ref{sec:edge}.} |
| 10 |
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|
| 11 |
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The production of Z bosons is expected in many BSM scenarios, for example supersymmetric (SUSY) |
| 12 |
< |
models. For example, Z bosons may be produced in the decays $\chi^0_2\to Z \chi^0_1$ |
| 13 |
< |
$\chi^0_1\to Z \tilde{G}$, where $\chi^0_2$ is the second lightest neutralino, $\chi^0_1$ is |
| 14 |
< |
the lightest neutralino, and $\tilde{G}$ is the gravitino. Such decays may occur in the cascade |
| 12 |
> |
models. In SUSY models with neutralino lightest SUSY particle (LSP), Z bosons may be produced in the decays $\chi^0_2\to Z \chi^0_1$, |
| 13 |
> |
where $\chi^0_2$ is the second lightest neutralino and $\chi^0_1$ is |
| 14 |
> |
the lightest neutralino. |
| 15 |
> |
In models with gravitino LSP such as gauge-mediated SUSY breaking (GMSB) models, Z bosons may be produced via |
| 16 |
> |
$\chi^0_1\to Z \tilde{G}$, where $\tilde{G}$ is the gravitino. Such decays may occur either in the cascade |
| 17 |
|
decays of the strongly-produced squarks and gluinos, or via direct production of the electroweak |
| 18 |
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charginos and neutralino. Examples of such processes (see Fig.~\ref{fig:diagrams}) are: |
| 19 |
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|
| 39 |
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|
| 40 |
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We thus pursue two strategies. The first is an inclusive strategy which selects events with a Z$\to\ell\ell$ candidate, |
| 41 |
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at least two jets, and large \MET. This strategy is useful for targeting, e.g., the production of Z bosons in the |
| 42 |
< |
cascades decays of strongly-interacting particles as depicted in Fig.~\ref{fig:diagrams} (left). In the second strategy, |
| 42 |
> |
cascade decays of strongly-interacting particles as depicted in Fig.~\ref{fig:diagrams} (left). In the second strategy, |
| 43 |
|
we impose additional requirements which strongly suppress the backgrounds while retaining high efficiency for events |
| 44 |
< |
with Z bosons produced via direct production of the weakly-coupled charginos and neutralinos. These two strategies |
| 45 |
< |
are referred to as the ``inclusive search'' and the ``targeted search,'' respectively. |
| 44 |
> |
with Z bosons produced via direct production of the weakly-coupled charginos and neutralinos. |
| 45 |
> |
These two strategies are referred to as the ``inclusive search'' and the ``targeted search,'' respectively. |
| 46 |
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|
| 47 |
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After selecting events with jets and a $\Z\to\ell^+\ell^-$ ($\ell=e,\mu$) candidate, |
| 48 |
|
the dominant background consists of SM \Z production accompanied by jets from initial-state radiation (\zjets). |
| 54 |
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\MET\ from jet mismeasurements. In this note, the \zjets\ background is estimated with the \MET templates technique, |
| 55 |
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in which the artificial \MET in \zjets events is modeled using a \gjets control sample. |
| 56 |
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The second background category consists of processes which produce leptons with uncorrelated flavor. |
| 57 |
< |
These ``flavor-symmetric'' (FS) backgrounds, which are dominated by \ttbar but also contain WW, DY$\to\tau\tau$ |
| 57 |
> |
These ``flavor-symmetric'' (FS) backgrounds, which are dominated by \ttbar\ but also contain WW, DY$\to\tau\tau$ |
| 58 |
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and single top processes, are estimated using a data control sample of e$\mu$ events. |
| 59 |
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Additional backgrounds from WZ and ZZ production are estimated from MC, after validation of the MC modeling |
| 60 |
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of these processes using 3-lepton and 4-lepton data control samples. |
