Safe Variables in tauRec

This page desribes the cut-based discriminant in tauRec with so-called Safe Variables
Current results can be found here: Safe Variables

Cut-based approach

There are two approaches available, one using only calorimeter information one combining calorimeter and tracking information.

Calo-approach

More safe approach, calorimeter will be well understood at very early stage (hopefully ).

Variable desription:

EMRadius (Radius in EM Calorimeter)
$\Large $R_{em}=\frac{\sum_{i=1}^{n}E_{T,i}\sqrt{\left(\eta_i-\eta_{cluster}\right)^2+\left(\phi_i-\phi_{cluster}\right)^2}}{\sum_{i=1}^{n}E_{T,i}}$$

Runs over all cells in the EM Calorimeter in a cluster with dR<0.4
IsoFrac (Isolation Fraction)
$\Large $\Delta E_T^{12}=\frac{\sum_i E_{T,i}}{\sum_j E_{T,j}}$$

Ring of 0.1<dR<0.2 as islolation region, i and j run over all EM cells in a cone with 0.1<dR<0.2 and dR<0.4
stripWidth2 (Width in strip layer)
$\Large $\Delta\eta=\sqrt{\frac{\sum_{i=1}^n E_{T,i}^{strip}\left(\eta_i-\eta_{cluster}\right)^2}{\sum_{i=1}^n E_{T,i}^{strip}}}$$

Transverse energy width in strip layer (fist layer of EM barrel)
EtEMEt (Fraction of transverse energy in the EM Calorimeter and total Et)
$\Large $\Delta E_T^{EM/tot}=\frac{E_T^{EM}}{E_T^{total}}$$

Fraction of transverse energy in the EM calorimeter and the total transverse energy

Histograms for Calo-approach:

Calo+Track-approach

More aggressive approach with better rejection power.

Variable description:

RWidth2Trk3 (Width of track momenta)
$\Large $W_{track}^{\tau}=\frac{\sum\left(\Delta\eta^{\tau,track}\right)^2\cdot p_T^{track}}{\sum p_T^{track}}-\frac{\sum\left(\Delta\eta^{\tau,track}\cdot p_T^{track}\right)^2}{\left(\sum p_T^{track}\right)^2}$$

Width of tracks, weighted with their transverse momenta
etOverPtLeadTrack (Fraction of pT and Et of leading track)
$\Large $\Delta E_T^{p_{T,1}}\frac{E_T^{total}}{p_{T,1}}$$

Large fraction of tau energy is expected to be carried by the leading track
EtEMsumpT
$\Large $\Delta E_T^{EM/p_T}=\frac{E_T^{EM}}{p_T^{total}}$$

Fraction of transverse energy in the EM Calorimeter and total pT
EtEMsumpT
$\Large $\Delta E_T^{Had/p_T}=\frac{E_T^{Had}}{p_T^{total}}$$

Fraction of transverse energy in the EM Calorimeter and total pT
sumpTEt
$\Large $\Delta p_T^{E_T}=\frac{p_T^{total}}{E_T^{total}}$$

Fraction of total transverse momenta and total transverse energy

Histograms for Calo+Track-approach:

Data samples

Several signal and background data samples from release 14.2.0 production were used for the optimization of the safe variables. The tables below give the number of events and cross-section for these samples.

Signal:

Dataset ID	channel	number events	x-section
005188	Z->tautau	131500	$$\rm 1.64\cdot10^{3}$ pb$
005862	bbA(800)->tautau	66750	$$\rm 0.0152$ pb$

Background:

Dataset ID	channel	number events	x-section
005010	Di-jet J1 (17-35 GeV)	78500	$$\rm 1.38\cdot10^{9}$ pb$
005011	Di-jet J2 (35-70 GeV)	141000	$$\rm 93.3\cdot10^{6}$ pb$
005012	Di-jet J3 (70-140 GeV)	123950	$$\rm 5.88\cdot10^{6}$ pb$
005014	Di-jet J5 (280-560 GeV)	116200	$$\rm 12.5\cdot10^{3}$ pb$

For the distribution and performance plots the J5 was excluded and the samples were weighted to $\rm 1 pb^{-1}$

PUB Note

Distribution plots
Performance plots
Performance tables

If you have questions please contact Björn Gosdzik

ATLAS: Projects/SimRec/TauID/SafeVariables (last edited 2009-11-23 09:17:53 by BjoernGosdzik)