Tau Public Results from Cut-based Identification method

Introduction

This page shows the results of the optimisation of a cut-based identification method for tau leptons in the ATLAS detector. Two methods were optimised:

• a calorimeter identification method using variables derived from calorimeter deposits only
• and a calorimeter+track identification method extending the calorimeter method with variables from the Inner Detector.

Only variables that will be well understood in early data taking (robust variables) are used, therefore variables depending on precision tracking, π⁰ reconstruction or energy flow calculation are avoided.

Both methods were separately optimised for decays with one charged particle (1-prong) and three charged particles (3-prong). Furthermore the optimisation was splitted into five Et bins:

• 10 - 25 GeV
• 25 - 45 GeV
• 45 - 70 GeV
• 70 - 100 GeV
• > 100 GeV

We used Pythia Z->tautau and bbA(800)->bbtautau (for high pT taus) samples as signal and several Pythia di-jet samples with a momentum transfer at hard scatter ranging from 17 - 560 GeV for the background.

Three types of optimisation are defined for each method:

• tight corresponding to a signal efficiency of approximately 30%
• medium corresponding to a signal efficiency of approximately 50%
• loose corresponding to a signal efficiency of approximately 70%

The plots on this page show the distribution of the identification variables for signal and background in the Et bin 25 - 45 GeV for 1-prong and 3-prong tau candidates. Futhermore the performance for both methods is shown, separately for both decay modes (1-prong and 3-prong) and all five Et bins.

All plots provided on this page are summarised in ATL-PHYS-PUB-2010-001

Contacts for these plots: atlas-perf-tau-conveners@cernNOSPAMPLEASE.ch

Calorimeter and tracking variables

Electromagentic radius
	eps-Version		eps-Version
1-prong tau candidates		3-prong tau candidates
Transverse energy width in the eta strip layer
	eps-Version		eps-Version
1-prong tau candidates		3-prong tau candidates
Isolation Fraction
	eps-Version		eps-Version
1-prong tau candidates		3-prong tau candidates
Ratio of EM energy and total energy
	eps-Version		eps-Version
1-prong tau candidates		3-prong tau candidates
Et over pT of the leading track
	eps-Version		eps-Version
1-prong tau candidates		3-prong tau candidates
Ratio of EM energy and sum of pT of tracks
			eps-Version
		3-prong tau candidates
Ratio of Had energy and sum of pT of tracks
Ratio of the transverse energy in the hadronic calorimeter and the sum of the transverse momenta
			eps-Version
		3-prong tau candidates
Ratio of sum of pT of tracks and total energy
			eps-Version
		3-prong tau candidates
Track spread
			eps-Version
		3-prong tau candidates

Performance of calorimeter method

10 - 25 GeV
	eps-Version		eps-Version
1-prong tau candidates		3-prong tau candidates
25 - 45 GeV
	eps-Version		eps-Version
1-prong tau candidates		3-prong tau candidates
45 - 70 GeV
	eps-Version		eps-Version
1-prong tau candidates		3-prong tau candidates
70 - 100 GeV
	eps-Version		eps-Version
1-prong tau candidates		3-prong tau candidates
> 100 GeV
	eps-Version		eps-Version
1-prong tau candidates		3-prong tau candidates

Performance of calorimeter+track method

10 - 25 GeV
	eps-Version		eps-Version
1-prong tau candidates		3-prong tau candidates
25 - 45 GeV
	eps-Version		eps-Version
1-prong tau candidates		3-prong tau candidates
45 - 70 GeV
	eps-Version		eps-Version
1-prong tau candidates		3-prong tau candidates
70 - 100 GeV
	eps-Version		eps-Version
1-prong tau candidates		3-prong tau candidates
> 100 GeV
	eps-Version		eps-Version
1-prong tau candidates		3-prong tau candidates

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Major updates:
-- BjoernGosdzik - 12-Mar-2010

Responsible: BjoernGosdzik
Last reviewed by: Never reviewed