1Eric Torrence January 2009

Oregon Tau Activities

• Tau Trigger Efficiency

• Z→ττ

• Dijet Fakes

• Tau Spin Analysis

• Tau Trigger Activities

• Validation

• HLT Monitoring

• TTP Ntuples

2Eric Torrence April 2009

Efficiency Motivation

Why measure trigger efficiency at all?Physics

• Typically need product ε(trig) x ε(reco)

• Sometimes need ε(reco) alone

• Never (?) need ε(trig) alone

Can factorize and measure ε(trig) / ε(reco)

Trigger Understanding

• Trigger must be understood/commissioned beforefirst “real” taus are seen

Both need ε(trig) dependence on key variables

3Eric Torrence May 2008

Analysis Overview

Z→ττ→lh (Oregon, Uppsala)

• Motivated by analysis in offline Tau note (and before)

• Try to optimize for trigger efficiency measurement

• Check results - get experience with analysis

Fake offline taus in jet events (Oregon, UIUC)

• Motivated by D0 analysis

• High statistics monitoring analysis

• Possible to make real efficiency measurement?

4Eric Torrence May 2008

Z→ττ Overview

• Start with lepton trigger: electron or muon

• Offline object selection:electron loose/medium/tight, Staco muon, tau 1p3p (cut-based for now) in |eta|<2.5

• Remove overlaps (mu, electron, tau priority)Should use offline tools here...

• Reconstruct Z momentum using MET technique

• Cut on Z mass to improve purity

• Additional cuts also explored (motivated by note)includes MET, tau-lept angle

Verify results in offline note, explore background estimation

Look at improvements or biases for trigger efficiency

5Eric Torrence May 2008

Typical Results

• Select 240 signal 60 < mRec < 120 in 100 pb-1

• Entirely based on private code from ntuples

• Will integrate trigger efficiency effort into broader SMbenchmark Z→ττ→lh analysis framework

Reco Mass (GeV)

MC

EventsSignalTight Electron (Pt > 15)tau1p3p (Pt > 10)MET > 20, m(tau-l), angles

6Eric Torrence May 2008

Current Work

• Looking at bias in extracted efficiency due to e.g.: MET cut

• Considering simpler “visible mass” observable - less dependence on MET, better resolution, possibly no worse that what we are using now.

True Efficiency vs. Etfor different MET cuts

No additional bias apparent!

7Eric Torrence May 2008

Efficiency from fakes

• Lots of di-jet events pass offline tau selection(minbias fake rate ~ 0.1%)

• If they look this much like taus, they had betterfire the tau trigger

• Probably not a high-accuracy measurement, but shouldprovide lots of statistics

Expect 430 tau events/12 hours with nominal10 Hz minbias trigger, possibly more with

pre-scaled jet triggers.

8Eric Torrence April 2009

Fake 3pr taus

10 TeV W→τν vs.J0-J4 unweighted

tauRec L>5

Good to ~5-10%

L1 L2

EF

Reco EtReco Et

Reco Et

9Eric Torrence April 2009

Fake 1pr taus

10 TeV W→τν vs.J0-J4 unweighted

tauRec L>5

Good to ~10-20%

Reco EtReco Et

Reco Et

10

Eric Torrence January 2009

Other Activities

• Tau Polarization (Robinson/Frey)

• Use tau decay properties to spin-analyze tau production

• Current work done for Z’ by NBI-Copenhagen

• Likely long-term project (not for first data)

• Tau Trigger Validation (Robinson/Reinsch/Strom)

• Oregon responsible for HLT software validation

• Lots of (not very glamorous) work

• Tau Trigger Monitoring/Commissioning (Shamim/Torrence)

• Tau Trigger group ntuples and analysis code

• Responsibility for tau trigger monitoring