Alec Aivazis edited eventSelection.tex  over 9 years ago

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\section{Event selection and Monte Carlo simulation}\label{sect:eventSelection}  Each event is processed using a global event reconstruction algorithm which reconstructs and indentifies the particles using information from all of the subdetectors as described in section \ref{sect:CMS} \cite{Khachatryan_2014}. \ref{sect:CMS}.  It is important to note that this algorithm relies heavily on the identifacation the particle type (photon, electron, muon, hadron) to reconstruct the trajectory of the particle \cite{Khachatryan_2014}. After events are reconstructed, they are selected from an online dilepton trigger (events only include those whose final state are $ee$, $e\mu$, $\mu e$, and $\mu\mu$) which requires the tranverse momentum ($p_T$) of the largest lepton to be greater than 17 GeV and the smaller to be greater than 8 GeV. The reconstructed trajectories (known as hypotheses) are then grouped together according to the location in the LHC where the interaction occured. This is done to prevent particles that originated in other interactions (pileup) from being considered as part of the final state. Each hypothesis is restricted to having $p_T >$ 20 GeV, oppositely charged leptons, $|\eta| < 2.4$ where $\eta \equiv - \ln{\frac{\theta}{2}}$, not be an $ee$ event, and have a total minimum invariant mass of 20 GeV. A minimum isolation is also required according to the loose working points of the combined secondary vertex (CSV) algorithm \cite{Khachatryan_2014}. The hypothesis with the highest combined $p_T$ bewtween the two leptons that passes these criteria is then taken to be the primary interaction at the corresponding LHC bunch crossing.