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\section{CMS detector}
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%The following is copied from published ttdilepton paper
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The central feature of the CMS apparatus is a superconducting
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solenoid, 13~m in length and 6~m in diameter, which provides
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an axial magnetic field of 3.8 T. Within the field volume are
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several particle detection systems.
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Charged particle
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trajectories are measured with silicon pixel and strip trackers,
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covering $0 \leq \phi < 2\pi$ in azimuth and $|\eta| < 2.5$ in pseudorapidity,
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where $\eta = -\ln [\tan (\theta/2)]$ and $\theta$ is the
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polar angle of the trajectory of the particle with respect to
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the counterclockwise proton beam direction. A lead tungstate crystal electromagnetic calorimeter
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and a brass/scintillator hadron calorimeter surround the
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tracking volume, providing energy measurements of electrons and
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hadronic jets. Muons are identified and measured in gas-ionization detectors embedded in
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the steel flux return yoke of the solenoid. The CMS detector is nearly
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hermetic, allowing momentum balance measurements in the plane
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transverse to the beam direction. A two-tier trigger system selects pp collision events
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of interest for use in physics analyses.
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A more detailed description of the CMS detector can be found
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elsewhere~\cite{JINST}.
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%The central feature of the CMS apparatus is a superconducting solenoid,
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%of 6~m internal diameter, providing a field of 3.8~T. Within the field
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%volume are the silicon pixel and strip tracker, the lead-tungstate crystal electromagnetic
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%calorimeter (ECAL) and the brass/scintillator hadron calorimeter (HCAL).
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%Muons are measured in gas-ionization detectors embedded in the steel return yoke.
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%Charged particle trajectories are measured by the silicon pixel and strip tracker, covering $0 < \phi < 2 \pi$ in azimuth and $|\eta| < 2.5$, where the pseudorapidity $\eta$ is defined as $\eta = -log(tan(\theta/2))$, with $\theta$ being the polar angle of the trajectory of the particle.
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%The ECAL has an energy resolution of better than 0.5\,\% above 100\GeV.
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%The HCAL, when combined with the ECAL, measures jets with a resolution
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%$\Delta E/E \approx 100\,\%\sqrt{E\,[\GeV]} \oplus 5\,\%$.
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%The calorimeter cells are grouped in projective towers, of granularity
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%$\Delta \eta \times \Delta \phi = 0.087\times0.087$ at central rapidities
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%and $0.175\times0.175$ at forward rapidities.
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%Muons(electrons) are measured in the pseudorapidity range of $|\eta|< 2.4$ ($2.5$) respectively.
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%More details about the CMS detector can be found elsewhere~\cite{JINST}.
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