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Standard Cut Analysis : Bdt Systematics

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\chapter{BDT Systematics} % **************************** Define Graphics Path ************************** The main sources of systematics uncertainties come from: \begin{itemize} \item uncertainties in detector acceptances, calibration or resolution, \item uncertainties in the underlying theoretical models, \item mismodeled background, and \item uncertainties in input parameters, e.g. flux uncertainties. \end{itemize} The systematic uncertainties, in an electron anti-neutrino cross section measurement at ND280, will be fully described in~\cref{ch:SysUncertainty}. An important question in the multivariate classification techniques is how to address systematic uncertainties, and if multivariate techniques are more prone to systematics …show more content…

\item The main objective of the analysis is to measure the $\overline{\nu}_e$ cross-section, and the systematics uncertainty on this quantity will be evaluated by MC simulation by varying all the inputs. Hence, a direct measurement of tBDT systematic is not needed. \end{itemize} The second approach is to evaluate the effect of input variables systematic on the performance of the trained BDT, or more precisely on the purity and efficiency of the selection. To achieve these goals, the BDT output distribution and training performance (purity and efficiency of the selection) are calculated using test samples of input variables with all possible systematic variations. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% \section{Uncertainty On The BDT Output Distribution} \subsection{Data/MC Agreement} So far, only the detector systematics was taken into consideration, since we are working on the same Monte Carlo (MC). The theoretical model and background systematics are probed by overlaying the BDT output (tBDT) distribution for the simulated signal and background with the tBDT distribution calculated for the data, as shown in~\cref{fig:BDT_tBDT_DataMC}.

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