| 1 |
|
\section{Search in the All-Hadronic Final State} |
| 2 |
|
\label{sec:alphat} |
| 3 |
|
|
| 4 |
< |
The production of bottom squark pairs, followed by the decay $\tilde{b}\to b\lsp$, leads events with |
| 5 |
< |
two b-jets and \met. In this section we report the results from a search in the all-hadronic final state using the |
| 4 |
> |
\begin{figure*}[!ht] |
| 5 |
> |
\centering |
| 6 |
> |
%\begin{center} |
| 7 |
> |
\begin{tabular}{cc} |
| 8 |
> |
\subfloat[] {\includegraphics[width=0.45\textwidth]{HCPPlots/AlphaT_le3j_prelim.pdf}} & |
| 9 |
> |
\subfloat[] {\includegraphics[width=0.4\textwidth]{HCPPlots/hadronic_2b_le3j_logy.pdf}} \\ |
| 10 |
> |
\end{tabular} |
| 11 |
> |
\caption{ |
| 12 |
> |
The distribution of the \alphat\ variable (left) and the $H_T$ distribution in data, compared to the SM background expectation (right). |
| 13 |
> |
\label{fig:alphat} |
| 14 |
> |
} |
| 15 |
> |
%\end{center} |
| 16 |
> |
\end{figure*} |
| 17 |
> |
|
| 18 |
> |
The production of bottom squark pairs, followed by the decay $\tilde{b}\to b\lsp$, leads to events with |
| 19 |
> |
two b-jets and \met. In this section we report the results from a search with 11.7 fb$^{-1}$ |
| 20 |
> |
in the all-hadronic final state using the |
| 21 |
|
\alphat\ variable, discussed below, which discriminates between backgrounds with real and fake \met. |
| 22 |
|
|
| 23 |
|
We require at least two jets with \pt\ $>$ 50 GeV. The leading (highest \pt) jet is required to be in the tracker |
| 32 |
|
of the second leading jet and $M_T$ is the transverse mass of the dijet system. |
| 33 |
|
For events with perfectly measured jets, the measured \pt\ values of the two jets are equal, leading to $\alphat=0.5$. The key feature of the \alphat\ variable |
| 34 |
|
is that mismeasurement effects tend to decrease the value of \alphat, such that it is extremely rare for events with fake \met\ to have \alphat\ |
| 35 |
< |
much larger than 0.5; as shown in Fig.~\ref{fig:alphat}a, the \alphat\ distribution for the QCD multijet background falls off extremely rapidly near 0.5. |
| 35 |
> |
much larger than 0.5. As shown in Fig.~\ref{fig:alphat}(a), the \alphat\ distribution for the QCD multijet background falls off extremely rapidly near this endpoint value. |
| 36 |
|
For events with three of more jets, an equivalent dijet system is formed by clustering the jets into two pseudo-jets. In our search we strongly suppress the |
| 37 |
|
QCD multijet background with the requirement \alphat\ $>$ 0.55. |
| 38 |
|
|
| 40 |
|
where the lepton is either not reconstructed or is a hadronically decaying $\tau$ lepton. |
| 41 |
|
These backgrounds are estimated using a $\mu+\rm{jets}$ data control sample. |
| 42 |
|
The additional background from $\rm{Z}(\nu\nu)+\rm{jets}$ is estimated using two data control samples of $\rm{Z}(\ell\ell)+\rm{jets}$ and $\gamma+\rm{jets}$ events. To estimate these backgrounds, the observed yields in the data control samples are extrapolated to the |
| 43 |
< |
signal region using translation factors derived from MC. The dominant systematic uncertainty in the background prediction is the uncertainty |
| 44 |
< |
in the MC translation factors, which are assessed by performing several closure tests in data, in which the observed yields in one data control region |
| 43 |
> |
signal region using translation factors derived from MC. The dominant systematic uncertainties in the background prediction stem from the uncertainties |
| 44 |
> |
in the MC translation factors, which are assessed by performing several closure tests in data. In these tests, the observed yields in one data control region |
| 45 |
|
are used to predict the yields in another data control region. |
| 46 |
|
|
| 47 |
|
Events are categorized based on the $H_T$, jet multiplicity, and b-tagged jet multiplicity. For the bottom squark scenario described above, the most sensitive |
| 48 |
< |
category is events with either two or three jets and exactly two b-tagged jets. The $H_T$ distribution for these events is indicated in Fig.~\ref{fig:alphat}b, |
| 48 |
> |
category is events with either two or three jets and exactly two b-tagged jets. The $H_T$ distribution for these events is indicated in Fig.~\ref{fig:alphat}(b), |
| 49 |
|
which demonstrates good agreement between the data and the expected background. No evidence for an excess of events is observed. |
| 50 |
|
|
| 51 |
|
The results are interpreted using the model of bottom squark pair production with $\tilde{b}\to b\lsp$ in Fig.~\ref{fig:ss_interpretation}(b). |
| 52 |
|
These results probe bottom squarks with masses up to approximately 600 GeV. Additional interpretations in models with gluino-mediated |
| 53 |
|
top and bottom squark pair production are presented in Ref.~\cite{ref:alphat}. |
| 54 |
|
|
| 40 |
– |
\begin{figure*} |
| 41 |
– |
\centering |
| 42 |
– |
%\begin{center} |
| 43 |
– |
\begin{tabular}{cc} |
| 44 |
– |
\includegraphics[width=0.45\textwidth]{HCPPlots/AlphaT_le3j_prelim.pdf} & |
| 45 |
– |
\includegraphics[width=0.45\textwidth]{HCPPlots/hadronic_2b_le3j_logy.pdf} \\ |
| 46 |
– |
\end{tabular} |
| 47 |
– |
\caption{ |
| 48 |
– |
The distribution of the \alphat\ variable (left) and the $H_T$ distribution in data, compared to the SM background expectation (right). |
| 49 |
– |
\label{fig:alphat} |
| 50 |
– |
} |
| 51 |
– |
%\end{center} |
| 52 |
– |
\end{figure*} |
