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\begin{document}
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\Title{Inclusive searches for supersymmetric signatures with the ATLAS detector}

\bigskip\bigskip

%+\addtocontents{toc}{{\it D. Reggiano}}
%+\label{ReggianoStart}

\begin{raggedright}  

{\it Enrique Kajomovitz\index{Kajomovitz E.}\\
On behalf of the ATLAS collaboration\\
Physics Faculty, Technion - Israel Institute of Technology\\
Haifa 32000, ISRAEL}
\bigskip\bigskip
\end{raggedright}


\section{Introduction}
A brief summary of recent results on inclusive searches for supersymmetry (SUSY) and of searches for SUSY signatures involving long-lived massive particles is presented. The reported results use up to 4.7 fb$^{-1}$ of data from $pp$ collisions at center-of-mass energy of $\sqrt{s} =7$ TeV recorded in 2011 by ATLAS\cite{ATLAS-2008} at the LHC.

%\section{Supersymmetry searches}

Strong SUSY production is searched in events with large jet multiplicities and large missing transverse momentum, with and without leptons.
SUSY with $\tilde{\tau}$ as next to lightest SUSY particle (NLSP) is searched in events with one or more $\tau$ leptons and missing transverse momentum.
SUSY with meta-stable charginos is searched in events with missing transverse momentum and a disappearing track.
Table (\ref{tab:signatures_models}) lists the searches presented.

\begin{table}[hbp]
  \begin{center}
    \begin{tabular}{l l l l }
      Signature & Model & $\int{\mathcal{L}}dt$ & Ref. \\
 \hline
  0-lep + $E^{\mathrm{miss}}_\mathrm{T}$ +$\geq$ (2-6) jets & medium to large mass splittings & 4.7 fb$^{-1}$  & \cite{ATLAS-26jets-2012} \\
  0-lep + $E^{\mathrm{miss}}_\mathrm{T}/\sqrt{H_\mathrm{T}}$ + $\geq$ (6-9) jets & long decay chains, $\tilde{g} \rightarrow t \bar{t} \tilde{\chi}^0$ & 4.7 fb$^{-1}$  & \cite{ATLAS-69jets-2012} \\
  $\geq$ 1-lep + $E^{\mathrm{miss}}_\mathrm{T}$ + $\geq$ (3,4) jets & decays with intermediate $\tilde{\chi ^\pm},\tilde{\chi ^0}, \tilde{\ell } $ & 4.7 fb$^{-1}$   & \cite{ATLAS-1lep_jets-2012} \\
  2-lep (S.S.) + $E^{\mathrm{miss}}_\mathrm{T}$ + $\geq$ 4 jets & $m_{\tilde{g}} \sim m_t + m_t + m_{\tilde{\chi}^0}$ & 2.1 fb$^{-1}$  & \cite{ATLAS-2ssl-2012} \\
  $\geq$1-tau + $E^{\mathrm{miss}}_\mathrm{T}$ + jets & GMSB with $\tilde{\tau}$ NLSP & 2.1 fb$^{-1}$  & \cite{ATLAS-1tau-2012} \\
  $\geq$2-tau + $E^{\mathrm{miss}}_\mathrm{T}$ + jets & GMSB with $\tilde{\tau}$ NLSP & 2.1 fb$^{-1}$  & \cite{ATLAS-2tau-2012} \\
  Disappearing track & AMSB with meta-stable $\tilde{\chi}^{\pm}$ & 4.7 fb$^{-1}$  & \cite{ATLAS-llchargino-2012} \\
 \hline 

\end{tabular}
\end{center}
\caption{SUSY searches performed by ATLAS. The word \textit{lep} denotes an isolated electron or muon, \textit{S.S.} denotes same-sign leptons, \textit{tau} denotes hadronically  decaying $\tau$. }
\label{tab:signatures_models}
\end{table}

\section{Searches with jets and $E^{\mathrm{miss}}_\mathrm{T}$ }
The (2-6) jets search \cite{ATLAS-26jets-2012} is motivated by strong SUSY production of gluinos and squarks that subsequently decay to quarks and neutralinos. 
Events are selected based on a jet+$E^{\mathrm{miss}}_\mathrm{T}$ trigger, applying a lepton veto, requiring from (2-6) jets, $E^{\mathrm{miss}}_\mathrm{T} > 160$ GeV, 
and azimuthal separation between the $E^{\mathrm{miss}}_\mathrm{T}$ and reconstructed jets to reject multi-jet backgrounds.  
Events are analysed in five signal regions, based on jet multiplicity, and in eleven channels based on the five signal regions and $m_{\mathrm{eff}}$(incl.), 
defined to be the scalar sum of the transverse momenta of jets with $p_\mathrm{T} > 40$ GeV and $E^{\mathrm{miss}}_\mathrm{T}$. 
Fake $E^{\mathrm{miss}}_\mathrm{T}$ and $Z\rightarrow \nu\nu + jets$ backgrounds are estimated directly from data,  other backgrounds are estimated using  control regions to extrapolate Monte Carlo (MC) to the signal regions.
%\section{Search with 6-9 jets }

The (6-9) jets search \cite{ATLAS-69jets-2012}  is motivated by SUSY models with long decay chains, and models with a gluino decaying to a top quark pair and a neutralino. 
To avoid overlap with the (2-6) jet search, the trigger used to select events for this search is based on multiple jets instead of
$E^{\mathrm{miss}}_\mathrm{T}$. Events are selected using a lepton veto, requiring six to nine jets and  $E^{\mathrm{miss}}_\mathrm{T}$ significance,$E^{\mathrm{miss}}_\mathrm{T}/\sqrt{H_\mathrm{T}} > 4$ GeV$^{1/2}$. Multi-jet backgrounds are estimated from data by extracting the shape of the  
$E^{\mathrm{miss}}_\mathrm{T}/\sqrt{H_\mathrm{T}}$ from a control region with lower jet multiplicity and normalising it according to a control region with the same jet multiplicity but $E^{\mathrm{miss}}_\mathrm{T}/\sqrt{H_\mathrm{T}} < 1.5$  GeV$^{1/2}$.
% The sub-dominant leptonic backgrond are estimated from MC and normalised according to a control region, and validated in a validation region. 

%\section{Search with 1 lepton and jets}

The 1-lepton search \cite{ATLAS-1lep_jets-2012} is motivated by models with  SUSY decay chains with intermediate  $\tilde{\chi ^\pm},\tilde{\chi ^0}, \tilde{\ell }$, for which an isolated lepton is a clean signature. 
Within this search ATLAS performs a soft-lepton analysis which enhances the sensitivity of the search (between twenty to thirty times) in the difficult kinematic region where the neutralino and gluino masses are close to each other. Events with an isolated lepton are selected according to jet multiplicity, $E^{\mathrm{miss}}_\mathrm{T}$, $m_{\mathrm{eff}}$, and $E^{\mathrm{miss}}_\mathrm{T}/m_{\mathrm{eff}}$. Backgrounds are determined in a simultaneous Profile Likelihood (PL) fit with nuisance parameters, which allow the determination of some theoretical uncertainties directly from data. Notable uncertainties determined from data are: the relative normalization of W+jets and Z+jets MC samples with different parton multiplicities, the uncertainty in the cross section of the vector boson plus heavy flavor production, the uncertainty on the $p^Z_\mathrm{T}$ distribution, and the uncertainty in the normalization of the W +jets and 	Z +jets 0-1 parton MC due to uncertainties in renormalization and factorization scales.
%Notable uncertainties determined from data are: the relative normalization
%of ALPGEN samples with different parton multiplicity, the uncertainty in
%the cross section of the vector boson
%\section{Search with two  same sign leptons and jets}

The two same charge (hereafter called 'same sign') lepton search \cite{ATLAS-2ssl-2012} is motivated by the equal probability of the majorana gluino to produce events with same sign and opposite sign leptons. 
A same sign lepton pair offers a clean signature, and enhances the sensitivity where the gluino mass is close to the combined mass of a top pair and the mass of the lightest neutralino. Events having two leading leptons with the same charge are selected based on 
jet multiplicity, $E^{\mathrm{miss}}_\mathrm{T}$, and $m_\mathrm{T}$ for one of the signal regions. 
%The dominant backgrounds to this search are $t\bar{t} + X$ events. Subleading backgrounds are events where a jet is missidentified as a lepton and events where a $b$ or $c$ decay is missidentified as a lepton. Other background contributions are di-boson events, and events where the charge of an electron is mis-identified.


%\section{Strong SUSY production limits}

Limits for strong SUSY production are set in the absence of deviations from the Standard Model (SM) predictions. Figure (\ref{fig:fig_2} - top left) illustrates the limits set under the MSUGRA/CMSSM framework. Squarks with masses below 1.4 TeV are excluded, and gluinos are excluded with masses below 800 GeV.
Results are also interpreted under simplified model assumptions,  Figure (\ref{fig:fig_2} - top right) illustrates the interpretation of the 6-9 jets result under the assumption of a simplified model where $\tilde{g}\tilde{g}$ are always produced, and each $\tilde{g}$ decays to $t\bar{t}+\tilde{\chi}^0$. 
%Figure (\ref{fig:fig_1lep_simplified}) illustrates the intepretation of the result of the 1-lepton search for the soft-lepton signal region under the assumption of a simplified model where $\tilde{g}\tilde{g}$ are always produced, and each $\tilde{g}$ decays to $qq+\tilde{\chi}^+$, and $\tilde{\chi}^+$ decays to $qq+W^++\tilde{\chi}^0$.



\section{Searches with  tau leptons, jets and $E^{\mathrm{miss}}_\mathrm{T}$ }
Two SUSY searches motivated by GMSB models with a $\tilde{\tau}$ NLSP are performed. Events are selected based on hadronically decaying $\tau$ leptons identified using Boosted decision trees (BDTs). One search \cite{ATLAS-1tau-2012}  selects events with  at least one $\tau$ lepton. Another search  \cite{ATLAS-2tau-2012} selects event with at least two $\tau$ leptons. Signal regions are defined according to $E^{\mathrm{miss}}_\mathrm{T}$, 
$m_{\mathrm{eff}}$, and
 $m_\mathrm{T}(E^{\mathrm{miss}}_\mathrm{T}, \tau)$. Since no deviation from the SM is seen, limits on contributions from new phenomena are set. Figure (\ref{fig:fig_2} - bottom left) illustrates the interpretation of the result of these two searches under the assumption of GMSB with $m_{\mathrm{mess}}=$250 TeV, $N_5=3$, $\mu > 0$, $C_{\mathrm{grav}} = 1$.

\begin{figure*}[tbp]
  \centering
  \includegraphics[width=0.25\linewidth]{limits_26_jets}
 \includegraphics[width=0.25\linewidth]{simplified_69} \\
  \includegraphics[width=0.25\linewidth]{GMSB_searches}
  \includegraphics[width=0.25\linewidth]{chargino_limit}
\caption{Top left - Exclusion plot in the MSUGRA/CMSSM \cite{ATLAS-26jets-2012}.  Top right - exclusion plot for simplified model (6-9) jet search \cite{ATLAS-69jets-2012}.
 Bottom left - Limits on GMSB models based on $\geq$1,2 tau searches \cite{ATLAS-2tau-2012}. 
 Bottom right - Limits on meta- stable charginos based on the disappearing track search \cite{ATLAS-llchargino-2012}. }
\label{fig:fig_2}
\end{figure*}

\section{Search with a disappearing track}
The search for SUSY with a disappearing track is motivated by AMSB models where the chargino can live long enough to be detected.
The search aims at detecting a chargino that decays within the inner detector volume. Since the chargino and the neutralino are very close in mass in these models, 
the charged particle(s) from the decay of this chargino are too soft to be reconstructed, therefore a disappearing track is expected. 
Events are selected based  on $E^{\mathrm{miss}}_\mathrm{T}$,
jet multiplicity and a lepton veto. Chargino candidates are selected requiring a good track quality before the TRT (outer part of the inner detector with a radius between 56 to 108 cm) and less than five hits in the TRT's outer module. Charginos with masses between 90 and 120 GeV are excluded for lifetimes above 10$^{-1}$ ns and below 10$^2$ ns. Figure (\ref{fig:fig_2} - bottom right) illustrates the limits obtained for the chargino. 

\section{Conclusion}

ATLAS has a thriving community with a strong and broad program searching for SUSY.
No evidence for SUSY has been found by ATLAS in the 4.7 fb$^{-1}$ recorded by ATLAS in 2011.
ATLAS will continue to look for evidence of SUSY.

\begin{thebibliography}{99}

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\bibitem{ATLAS-2008}
ATLAS Collaboration, 2008, {\it JINST} {\bf 3} S08003.

\bibitem{ATLAS-26jets-2012}
ATLAS Collaboration, 2012, Submitted to {\bf PRD}, \\ 
http://arxiv.org/abs/1208.0949 

\bibitem{ATLAS-69jets-2012}
ATLAS Collaboration, 2012, {\it JHEP} {\bf 1207} (2012) 167

\bibitem{ATLAS-1lep_jets-2012}
ATLAS Collaboration, 2012, Submitted to {\bf PRD}, \\ 
http://arxiv.org/abs/1208.4688

\bibitem{ATLAS-2ssl-2012}
ATLAS Collaboration, 2012, {\it PRL} {\bf 108} 241802 

\bibitem{ATLAS-1tau-2012}
ATLAS Collaboration, 2012, {\it PLB} {\bf 714} (2012) 197 

\bibitem{ATLAS-2tau-2012}
ATLAS Collaboration, 2012, {\it PLB} {\bf 714} (2012) 180 
 
\bibitem{ATLAS-llchargino-2012}
ATLAS Collaboration, 2012, ATLAS-CONF-2012-034, \\
https://cdsweb.cern.ch/record/1432200




\end{thebibliography}

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