Ryan Reece

ryan.reece@cern.ch

University of Pennsylvania

August 15, 2012ATLAS Exotics meeting, CERN

Approval of the

ATLAS combined Z’ → ττ

search with the 2011 data

on behalf of the Z’ → ττ analysis team:Will Davey (Bonn), Jochen Dingfelder (Bonn), Andres Florez (York), Julian Glatzer (Bonn), Gabriel

Palacino (York), Ryan Reece (Penn), Alex Tuna (Penn), Peter Wagner (Penn), Brig Williams (Penn)

and its editorial board:Yann Coadou (CNRS), Jean-Baptiste De Vive De Regie (Paris-Sud), Gideon Bella (Tel Aviv), Ashutosh

Kotwal (Duke)

Ryan Reece (Penn)

Introduction

2

• 2011 analysis Z’ → ττ →τhτh, µτh, eµ channels were

combined to exclude SSM of 1.3 TeV and were shown

at ICHEP 2012.

• eτh has now caught up and improved the combined

limit.

• minor updates to the τhτh and µτh channels.

Ryan Reece (Penn)

) [GeV]missTE, hτ, e(

totTm

0 500 1000 1500

Events

/ 5

0 G

eV

-210

-110

1

10

210

310

410ATLAS Preliminary

-1dt L = 4.6 fb∫ = 7 TeVs

(c)Data 2011

ττ→*γ/Z

+jetsZ/W

Multijet

ee→Z

tt

Dibosonsingle top

ττ→(1000)Z’

Z’ → ττ → eτh overview

3

Event selection

Dominant systematics

MT =

miss

miss

miss

Ryan Reece (Penn)

New systematics in plots• e →τh fake rate

uncert.≈ 50% Z→ee

• jet→τh fake factor

uncert.≈ 30% W+jet

• τh ID for Z→ττ ≈ 6%

• 100% multijet uncert.

• stat. uncert.

• hashing shows these

errors in quadrature

(nearly all the uncert.)4

Ele

ctr

ons /

(5 G

eV

)

0

50

100

data 2011

! ! "Z W/Z+jets

multijet

e e"Z

tt #W

dibosonsingle top

syst.$stat.

Z’(750)

Z’(1000)

Z’(1250)

ATLAS Internal-1dt L = 4.6 fb%

(e) [GeV]T

p

0 20 40 60 80 100 120 140obs.

/ exp.

0

1

2

• Systematics are “stacked”

in quadrature.

• Error bars are Poisson

Ryan Reece (Penn)

∆ϕ(τh ,e)

5

/30)

πE

vents

/ (

0

500

1000

1500

2000 data 2011

τ τ →Z W/Z+jets

multijet

e e→Z

tt γW

dibosonsingle top

syst.⊕stat.

Z’(750)

Z’(1000)

Z’(1250)

ATLAS Internal-1

dt L = 4.6 fb∫

, e)hτ(φ∆

0 0.5 1 1.5 2 2.5 3obs.

/ exp.

0

1

2

/30)

πE

vents

/ (

-110

1

10

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310

410

510data 2011

τ τ →Z W/Z+jets

multijet

e e→Z

tt γW

dibosonsingle top

syst.⊕stat.

Z’(750)

Z’(1000)

Z’(1250)

ATLAS Internal-1

dt L = 4.6 fb∫

, e)hτ(φ∆

0 0.5 1 1.5 2 2.5 3obs.

/ exp.

0

1

2

Figure 19: The distribution of the absolute difference in φ between the selected electron and hadronic

tau. These plots include the requirements of: exactly one selected electron, no additional

preselected electrons or muons, and exactly one selected 1-prong tau.

Ryan Reece (Penn)

ET

6

Events

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400

600

data 2011

τ τ →Z W/Z+jets

multijet

e e→Z

tt γW

dibosonsingle top

syst.⊕stat.

Z’(750)

Z’(1000)

Z’(1250)

ATLAS Internal-1dt L = 4.6 fb∫

[GeV]missTE

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/ exp.

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Events

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510 data 2011

τ τ →Z W/Z+jets

multijet

e e→Z

tt γW

dibosonsingle top

syst.⊕stat.

Z’(750)

Z’(1000)

Z’(1250)

ATLAS Internal-1dt L = 4.6 fb∫

[GeV]missTE

0 50 100 150 200 250 300350 400 450 500obs.

/ exp.

0

1

2

Figure 21: The distribution of transverse missing energy. These plots include the requirements of: ex-

actly one selected electron, no additional preselected electrons or muons, exactly one selected

1-prong tau, |∆φ(e, τh)| > 2.7, and opposite sign e and τh.

miss

miss

Ryan Reece (Penn)

Opposite sign

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150 data 2011

! ! "Z W/Z+jets

multijet

e e"Z

tt #W

dibosonsingle top

syst.$stat.

Z’(750)

Z’(1000)

Z’(1250)

ATLAS Internal-1dt L = 4.6 fb%

) [GeV]miss

T, E

h!(e, TM

0 50 100 150 200 250 300 350 400obs.

/ exp.

0

1

2

Events

/ (

10 G

eV

)

0

10

20

30data 2011

! ! "Z W/Z+jets

multijet

e e"Z

tt #W

dibosonsingle top

syst.$stat.

Z’(750)

Z’(1000)

Z’(1250)

ATLAS Internal-1dt L = 4.6 fb%

) [GeV]miss

T, E

h!(e, TM

0 50 100 150 200 250 300 350 400obs.

/ exp.

0

1

2

Opposite sign Same sign

Ryan Reece (Penn)

mT(e, ET )

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data 2011

τ τ →Z W/Z+jets

multijet

e e→Z

tt γW

dibosonsingle top

syst.⊕stat.

Z’(750)

Z’(1000)

Z’(1250)

ATLAS Internal-1dt L = 4.6 fb∫

) [GeV]miss

T(e, ETm

0 20 40 60 80 100 120140 160 180 200obs.

/ exp.

0

1

2

Events

/ (

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)

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410 data 2011

τ τ →Z W/Z+jets

multijet

e e→Z

tt γW

dibosonsingle top

syst.⊕stat.

Z’(750)

Z’(1000)

Z’(1250)

ATLAS Internal-1dt L = 4.6 fb∫

) [GeV]miss

T(e, ETm

0 100200 300 400 500 600700 800 9001000obs.

/ exp.

0

1

2

Figure 22: The distribution of transverse missing energy. These plots include the requirements of: ex-

actly one selected electron, no additional preselected electrons or muons, exactly one selected

1-prong tau, |∆φ(e, τh)| > 2.7, opposite sign e and τh, and EmissT> 30 GeV.

miss

miss

Ryan Reece (Penn)

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data 2011

τ τ →Z W/Z+jets

multijet

e e→Z

tt γW

dibosonsingle top

syst.⊕stat.

Z’(750)

Z’(1000)

Z’(1250)

ATLAS Internal-1dt L = 4.6 fb∫

) [GeV]miss

T, E

hτ(e, TM

0 50 100 150 200 250 300 350 400obs.

/ exp.

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Events

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410 data 2011

τ τ →Z W/Z+jets

multijet

e e→Z

tt γW

dibosonsingle top

syst.⊕stat.

Z’(750)

Z’(1000)

Z’(1250)

ATLAS Internal-1dt L = 4.6 fb∫

) [GeV]miss

T, E

hτ(e, TM

0 200 400 600 800 1000 1200 1400obs.

/ exp.

0

1

2

Figure 26: The distribution of the total transverse mass of the four-vector sum of the selected electron,

selected hadronic tau, and the transverse missing energy. These plots include the require-

ments of: exactly one selected electron, no additional preselected electrons or muons, ex-

actly one selected 1-prong tau, |∆φ(e, τh)| > 2.7, opposite sign e and τh, EmissT> 30 GeV, and

mT(e, EmissT) < 50 GeV.

mT(e, τh, ET )

9

misstot

misstot

Ryan Reece (Penn)

(e) [GeV]T

p

0 50 100 150 200 250 300 350 400

: m

ultije

te-iso

f

0

0.2

0.4

0.6

0.8

1

1.2

1.4Inclusive

Barrel

Endcap

ATLAS Internal

Multijet background estimation

10

Multijet control region

• In the control region, divide leptons

into pass and fail isolation.

• Define fake factor:

• Predict the number of QCD events:

fe–iso(pT, η) ≡Ne iso(pT, η)

Ne anti–iso(pT, η)

∣

∣

∣

∣

∣

∣

multijet–CR

Nmultijet(pT, η, x) = fe–iso(pT, η) · Ne anti–isomultijet (pT, η, x) .

We correct the sample of anti-isolated electrons in the data by subtracting the expected contamination ofx) = fe–iso(pT, η) ·(

Ne anti–isodata

(pT, η, x) − Ne anti–isoMC (pT, η, x)

)

.

Ryan Reece (Penn)) [GeV]

h!(

Tp

0 50 100 150 200 250

)h!

)+je

ts,

OS

(e,

" e

#

: W

(!

f

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

Inclusive

Barrel (inner)

Barrel (outer)

Endcap

ATLAS Internal

Events

/ (

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)

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1000

data 2011

! ! "Z W/Z+jets

multijet

e e"Z

tt #W

dibosonsingle top

syst.$stat.

Z’(750)

Z’(1000)

Z’(1250)

ATLAS Internal-1dt L = 4.6 fb%

) [GeV]miss

T(e, ETm

0 20 40 60 80 100 120140 160 180 200obs.

/ exp.

0

1

2

W+jet background estimation

11

W+jet control region

• In a W+jet control region, divide tau candidates into

pass and fail identification.

• Define fake factor:

• Predict the number of W/Z+jet events:

fτ(pT, η) ≡Npass τ−ID(pT, η)

Nfail τ−ID(pT, η)

∣

∣

∣

∣

∣

∣

W–CR

NW/Z+jet(pT, η, x) = fτ(pT, η) · Nfail τ−IDW/Z+jet (pT, η, x) ,

x) = fτ(pT, η) ·(

Nfail τ−IDdata (pT, η, x) − Nfail τ−IDmultijet (pT, η, x) − N

fail τ−IDMC (pT, η, x)

)

.

Ryan Reece (Penn)

Double fake factor procedure

12

!"#$%&

!"#$%&#'()*+(

,-.#&%$.&#$-.

!"#$%&#'

/01'#"

,-.#&%2

$.&#$-.

!"#$%&#'()*+(

,-.#&%$.&#$-.

'(#&"#")&(*+,-(./*01$.%2"$%."1$

'(#&"#")&(*+,-(./*01$.%2"$%."1$'1$3$(#&"#")&(*456*01$.%2"$%."1$

7%//*.%8*96

7%//*&(:.1$*"/1

!"#$%&"'%()

7%//*&(:.1$*"/1

7%//*.%8*96

!"#$%$*+&,-%#.,

!"#$%&"'%()

!"#$%$*+&,-%#.,

• The multijet contamination is estimated from the rate of non-isolated leptons, in

both the signal region that passes tau ID, and the sample that fails.

• Then, the corrected number of tau candidates failing ID are weighted to predicted

the W+jet background.

• This way, the corrections are small at each step.

Ryan Reece (Penn)

Events

/ (

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eV

)

0

500

1000

data 2011

τ τ →Z W/Z+jets

multijet

e e→Z

tt γW

dibosonsingle top

syst.⊕stat.

Z’(750)

Z’(1000)

Z’(1250)

ATLAS Internal-1dt L = 4.6 fb∫

) [GeV]miss

T(e, ETm

0 20 40 60 80 100 120140 160 180 200obs.

/ exp.

0

1

2

Ele

ctr

ons /

(0.0

2 m

m)

-110

10

310

510

710data 2011

τ τ →Z W/Z+jets

multijet

e e→Z

tt γW

dibosonsingle top

syst.⊕stat.

Z’(750)

Z’(1000)

Z’(1250)

ATLAS Internal-1dt L = 4.6 fb∫

(e) [mm]0

d

-1 -0.8-0.6-0.4-0.2 0 0.2 0.4 0.6 0.8 1obs.

/ exp.

0

1

2

Figure 28: (left) The distribution of the transverse mass of the combination of the selected electron and

the EmissT, mT(e, E

missT). in events with exactly one selected electron, no additional preselected

electrons or muons, and exactly one selected 1-prong tau. (right) The distribution of the

electron impact parameter, d0, in events with exactly one selected electron, no additional

preselected electrons or muons, and exactly one 1-prong tau candidate (without ID).

Control plots

13

Ryan Reece (Penn)

Cross-check: single fake factor method

14

!"#$%&

!"#$%&#'()*+(

,-.#&%$.&#$-.

!"#$%&#'

/01'#"

,-.#&%2

$.&#$-.

!"#$%&#'()*+(

,-.#&%$.&#$-.

'(#&"#")&(*+,-(./*01$.%2"$%."1$

'(#&"#")&(*+,-(./*01$.%2"$%."1$'1$3$(#&"#")&(*456*01$.%2"$%."1$

7%//*.%8*96

7%//*&(:.1$*"/1

!"#$%&"'%()

7%//*&(:.1$*"/1

7%//*.%8*96

!"#$%$*+&,-%#.,

!"#$%&"'%()

!"#$%$*+&,-%#.,

• Avoid issues of subtracting multijet from W/Z+jets background

• H→ττ uses a fake factor method covering all tau fakes from

W/Z+jets and multijet

• instead of estimating multijet independently with isolation fake factors

+

Ryan Reece (Penn)

Fake factors more quark-like at high-pT

15

1600 50 100 200 400 800 1600

Q

G

0%

100%

80%

60%

40%

20%

Z/W+1jet

pT Cut on All Jets (GeV)50 100 200 400 800 1600

G

Q

0%

100%

80%

60%

40%

20%

b+1jet

pT Cut on All Jets (GeV)

J. Gallicchio, M. Schwartz. “Pure Samples of Quark and Gluon Jets at the LHC”. arXiv:1104.1175

) [GeV]hτ(

Tp

0 50 100 150 200 250

)+je

ts

ν µ

→:

W(

τ f

0

0.02

0.04

0.06

0.08

0.1

Inclusive

)hτ, µOS(

)hτ, µSS(

ATLAS Internal

) [GeV]hτ(

Tp

0 50 100 150 200 250

: m

ultije

tτ

f

0

0.02

0.04

0.06

0.08

0.1

Inclusive

)hτ, µOS(

)hτ, µSS(

ATLAS Internal

our support note: ATLAS-CONF-2012-067

Ryan Reece (Penn)

Cross-check: single fake factor method

16

Events

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data 2011

! ! "Z W/Z+jets

multijet

e e"Z

tt #W

dibosonsingle top

syst.$stat.

Z’(750)

Z’(1000)

Z’(1250)

ATLAS Internal-1dt L = 4.6 fb%

Blin

ded

) [GeV]miss

T, E

h!(e, TM

0 50 100 150 200 250 300 350 400obs.

/ exp.

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1

2

Events

/ (

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80 data 2011

! ! "Z

h!fake

e e"Z

tt #W

dibosonsingle top

syst.$stat.

Z’(750)

Z’(1000)

Z’(1250)

ATLAS Internal-1dt L = 4.6 fb%

Blin

ded

) [GeV]miss

T, E

h!(e, TM

0 50 100 150 200 250 300 350 400obs.

/ exp.

0

1

2

double fake factor single fake factor

• as expected, the single fake factor method over-

estimates in regions where the multijet contamination

is large

Ryan Reece (Penn)

Cross-check: single fake factor method

17

Events

/ (

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)

0

5

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20 data 2011

! ! "Z

h!fake

e e"Z

tt #W

dibosonsingle top

syst.$stat.

Z’(750)

Z’(1000)

Z’(1250)

ATLAS Internal-1dt L = 4.6 fb%

Blin

ded

) [GeV]miss

T, E

h!(e, TM

200 250 300 350 400 450 500 550 600obs.

/ exp.

0

1

2

Events

/ (

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eV

)

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data 2011

! ! "Z W/Z+jets

multijet

e e"Z

tt #W

dibosonsingle top

syst.$stat.

Z’(750)

Z’(1000)

Z’(1250)

ATLAS Internal-1dt L = 4.6 fb%

Blin

ded

) [GeV]miss

T, E

h!(e, TM

200 250 300 350 400 450 500 550 600obs.

/ exp.

0

1

2

double fake factor single fake factor

double fake factor single fake factor

W/Z+jets multijet total fake τh

MT > 400 GeV 0.8(6) 0.3(3) 1.1(4) 1.3(4)

MT > 500 GeV 0.8(4) < 0.1 0.8(4) 0.9(4)

Ryan Reece (Penn)

Cross-check: single fake factor method

18

Events

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! ! "Z

h!fake

e e"Z

tt #W

dibosonsingle top

syst.$stat.

Z’(750)

Z’(1000)

Z’(1250)

ATLAS Internal-1dt L = 4.6 fb%

Blin

ded

) [GeV]miss

T, E

h!(e, TM

0 200 400 600 800 1000 1200 1400obs.

/ exp.

0

1

2

Events

/ (

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eV

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! ! "Z W/Z+jets

multijet

e e"Z

tt #W

dibosonsingle top

syst.$stat.

Z’(750)

Z’(1000)

Z’(1250)

ATLAS Internal-1dt L = 4.6 fb%

Blin

ded

) [GeV]miss

T, E

h!(e, TM

0 200 400 600 800 1000 1200 1400obs.

/ exp.

0

1

2

double fake factor single fake factor

double fake factor single fake factor

W/Z+jets multijet total fake τh

MT > 400 GeV 0.8(6) 0.3(3) 1.1(4) 1.3(4)

MT > 500 GeV 0.8(4) < 0.1 0.8(4) 0.9(4)

Ryan Reece (Penn)

eτh cut-flow

19

eτh µτh

data total SM Z → ττ W/Z+jets multijet Z → ee t t Wγ diboson single top Z′(1000)

one e, one τh 7295 7270(51) 1340(20) 3251(21) 766(22) 1280(35) 402(4) 68(6) 115(2) 49(2) 15.6(2)

|∆φ(e, τh)| > 2.7 3929 3933(43) 918(17) 1242(15) 556(18) 1020(32) 106(2) 28(4) 48(1) 15(1) 14.9(2)

opposite sign e and τh 3183 3322(40) 902(17) 1004(14) 279(13) 958(31) 99.9(2) 22(4) 44(1) 13.3(9) 14.6(2)

EmissT> 30 GeV 832 817(15) 158(6) 388(8) 39(6) 101(10) 85(2) 9(2) 26.8(9) 10.7(9) 12.8(2)

mT(e, EmissT

) < 50 GeV 263 298(10) 113(5) 101(5) 22(4) 41(6) 15.1(7) 1.3(9) 3.1(2) 1.9(3) 8.7(1)

MT > 200 GeV 46 59(4) 15.6(7) 31(2) 4(2) 0.03(2) 5.7(5) 0.6(6) 1.1(1) 0.8(2) 8.5(1)

MT > 300 GeV 14 14(2) 4.4(3) 6(1) 2(1) 0.02(2) 1.4(2) < 0.1 0.29(7) 0.11(8) 7.7(1)

MT > 400 GeV 4 3.0(8) 1.42(4) 0.8(6) 0.3(3) < 0.01 0.4(1) 0.14(5) < 0.1 6.5(1)

MT > 500 GeV 0 1.6(4) 0.57(2) 0.8(4) < 0.1 0.13(7) 0.06(3) 5.0(1)

MT > 600 GeV 0 0.5(2) 0.23(2) 0.2(2) 0.04(4) 0.02(2) 3.67(9)

Ryan Reece (Penn)

W+jets Z → ττ t t diboson Z′(1000)

expected events 0.8 0.6 0.1 0.1 5.0

total. uncert. 52 19 72 55 10

stat. uncert. 43 4 54 50 2

syst. uncert. 30 19 48 23 10

e efficiency - 1 1 1 1

e energy scale - 0 0 0 0

e energy resolution - 0 0 0 0

τh efficiency - 6 5 6 8

jet→ τh fake rate - 0 21 0 0

e→ τh fake rate - 0 23 17 0

jet energy scale - 14 24 11 6

jet energy resolution - 1 25 6 0

cluster energy scale - 0 5 0 1

luminosity - 2 2 2 2

theo. cross section - 11 10 7 -

τh fake factor 30 - - - -

eτh systematics

20

• statistics

• e→τh scale factors

• fake factor on

W+jets

• JES

(uncertainties in %)

Ryan Reece (Penn)

[GeV]Z’

m

500 1000 1500

) [p

b]

ττ

→Z’

(BR

×

) Z’

→pp

(σ

-310

-210

-110

1

ATLAS Preliminary-1

dt L = 4.6 fb∫ = 7 TeVs

channelhτµ

Expected limit

σ 1±Expected

σ 2±Expected

Observed limit

SSMZ’

[GeV]Z’

m

500 1000 1500

) [p

b]

ττ

→Z’

(BR

×

) Z’

→pp

(σ

-310

-210

-110

1

ATLAS Preliminary-1

dt L = 4.6 fb∫ = 7 TeVs

channelhτe

Expected limit

σ 1±Expected

σ 2±Expected

Observed limit

SSMZ’

µτh and eτh limits

21

• µτh: 1.06 (1.05) TeV

• eτh: 1.10 (1.02) TeV(BAT Bayesian limit)

Z’ SSM Exclusions: observed (expected) @ 95% CL

eτh channel has comparable

sensitivity to the µτh channel

eτh channelµτh channel

Ryan Reece (Penn)

eτh summary

22

• Adding the MET > 30 GeV helped decouple the

multijet contamination subtracted from the W+jet

estimate and further suppressed the Z→ee

background.

• Adding mT(e, MET) < 50 GeV suppressed the W+jet

background.

• Cross-checking with a single fake factor gave

consistent results and a conservative estimate of the

combined fake tau backgrounds.

µτh updates

Ryan Reece (Penn)

) [GeV]missTE, hτ, µ(tot

Tm

0 500 1000 1500

Events

/ 5

0 G

eV

-210

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1

10

210

310

410ATLAS Preliminary

-1dt L = 4.6 fb∫ = 7 TeVs

(b)Data 2011

ττ→*γ/Z

+jetsW

Multijet

µµ→Z

tt

Dibosonsingle top

ττ→(1000)Z’

Z’ → ττ → µτh overview

24

Event selection

Dominant systematics

miss

Ryan Reece (Penn)

µτh updates

25

• A few things have updated for the mu-had channel since the progress we made in the eτh channel.

• RootCore-00-00-33

• JetUncertainties-00-05-03

• |tau track eta| > 0.05 to update fiducial recommendation -- drops 1 event in the signal region

• systematics

• now using the new lumi uncertainty of 1.8% from ATLAS-CONF-2012-080

• The systematics were updated for µτh following the same strategy as for eτh of using a lower mass cut

(MT > 400 GeV) to evaluate the object-level systematic shifts, which gave more reasonable measure that

are statistically significant to a few percent instead of the previous statistically limit shifts. The main

changes were to things like JES and JER for diboson, which are now 2% instead of an insignificant 0.

Please note that the statistical errors still dwarf these object-level systematics.

• updated all the plots to now have systematics bands in the ratios

• In recent drafts the plots and tables were not yet updated for the change in luminosity; only the

final limit config was shifted. Plots and tables have been updated in

ZprimeTauTau2011COM-03-00-04

• no significant changes in background estimates.

Ryan Reece (Penn)

µτh updated limit

26

[GeV]Z’

m

500 1000 1500

[pb]

Bσ

-310

-210

-110

1

ATLAS Preliminary-1

dt L = 4.7 fb∫ = 7 TeVs

channelhτµ

Expected limit

σ 1±Expected

σ 2±Expected

Observed limit

SSMZ’

Old (CONF) New (Paper)

[GeV]Z’

m

500 1000 1500

) [p

b]

ττ

→Z’

(BR

×

) Z’

→pp

(σ

-310

-210

-110

1

ATLAS Preliminary-1

dt L = 4.6 fb∫ = 7 TeVs

channelhτµ

Expected limit

σ 1±Expected

σ 2±Expected

Observed limit

SSMZ’

• old: 1.00 (1.05) TeV

• new: 1.06 (1.05) TeV

Z’ SSM Exclusions: observed (expected) @ 95% CLMore toys giving higher resolution sampling of the bands in new limits, but expected and observed values do not change.

τhτh updatesWill Davey

Changes to τhτh analysis

• The only changes specific to the Z’→τhτh analysis involve the multijet estimate:

1. Included shape systematic uncertainty

2. Increased minimum of fit range to better avoid threshold effects

• The lumi central value and uncertainty was also updated (as for all channels)

• These changes have negligible effect on the final limit

28

Recap of method

29

Norm

aliz

ed e

vent

rate

/ 1

0 G

eV

0

0.05

0.1

0.15

0.2

0.25

0.3

ATLAS Preliminary-1

dt L = 4.7 fb! = 7 TeVs

Opposite Charge (OC)

Same Charge (SC)

) [GeV]missTE, h", h"(TM

200 250 300 350

OC

/ S

C

0.51

1.5

Fit same-sign (SS) data with dijet function:

Events

/ 4

0 G

eV

-110

1

10

210

310

410ATLAS Preliminary

-1dt L = 4.7 fb! = 7 TeVs

Data 2011Multijet

""#*$/Z

%"#W

Others""#(1250)Z’

) [GeV]missTE, h", h"(TM

500 1000 1500obs.

/ exp.

0.51

1.5

• OS/SS shapes agree well

• normalize in OS sideband with 160 < MT < 200 GeV

Changes

30

• raise the fit minimum to 200 GeV

• add additional shape systematic by comparing the fit result with a crystal ball function

[GeV]TM

0 200 400 600 800 100010!

Events

/ 2

0 G

eV

-210

-110

1

10

210

310

410

ATLAS Internal

QCD

Chi2/NDF: 7.60 / 11

700) = 0!(DataN

700) = 0.2!(FitN

old fit min too close to turn-on

region(not modelled by fitting functions)

new fit min

old fit min

[GeV]TM

0 200 400 600 800 1000 1200 1400 1600 1800 200010×

Events

-410

-310

-210

-110

1

10

210

310dijet function

crystal ball

Fit to SS region using nominal and alternate fit functions

high-mass counting region

Summary of fitting changes

• For Z’ signal masses of 500 and 625 GeV:

• nothing changed

• For signal masses mZ’ ≥ 750 GeV:

• Changed minimum of fit range from 160 → 200

• Changed side-band from [160,200] → [200,250]

31

) [GeV]missTE, h

!, h!(tot

Tm

200 400 600 800 1000

Events

/ 2

0 G

eV

-210

-110

1

10

210

310 ATLAS Preliminary

-1dt L = 4.7 fb" = 7 TeVs

/ NDF: 9.43 / 132#

700) = 0$TM(DataN

700) = 0.3$TM(FitN

) [GeV]missTE, h

!, h!(tot

Tm

200 400 600 800 1000

Events

/ 2

0 G

eV

-210

-110

1

10

210

310 ATLAS Preliminary

-1dt L = 4.6 fb" = 7 TeVs

/ NDF: 7.60 / 112#

700) = 0$TM(DataN

700) = 0.2$TM(FitN

Old New

Change in final estimates

32

Mass Point [GeV] 500 625 750-875 1000-1125 ≥1250

estimate 28.5 12.7 3.2 0.59 0.36

shape stat. uncertainty+3.1 -3.4

+2.2-2.5

+0.65-0.75

+0.16-0.20

+0.11-0.13

Mass Point [GeV] 500 625 750-875 1000-1125 ≥1250

estimate 28.5 12.7 2.7 0.42 0.24

shape stat. uncertainty +3.1-3.4

+2.2-2.5

+0.96-0.72

+0.30-0.16

+0.20-0.10

shape sys. uncertainty 1.1 0.9 0.02 0.02 0.02

norm. stat. uncertainty 0.7 0.6 0.13 0.02 0.01

Old multijet estimate

New multijet estimate

New multijet estimate has a slightly lower central value and slightly larger absolute uncertainty

[GeV]Z’

m

500 1000 1500

) [p

b]

ττ

→Z’

(BR

×

) Z’

→pp

(σ

-310

-210

-110

1

ATLAS Preliminary-1

dt L = 4.6 fb∫ = 7 TeVs

channelhτhτ

Expected limit

σ 1±Expected

σ 2±Expected

Observed limit

SSMZ’

τhτh updated limits

Changes do not significantly effect the limit

33

[GeV]Z’

m

500 1000 1500

[pb]

B!

-310

-210

-110

1

ATLAS Preliminary-1

dt L = 4.7 fb" = 7 TeVs

channelh#h#

Expected limit

! 1!Expected

! 2!Expected

Observed limit

SSMZ’

Old (CONF) New (Paper)

More toys giving higher resolution sampling of the bands in new limits, but expected and observed values do not change.

1.25 (1.35) TeV

Ryan Reece (Penn)

[GeV]Z’

m

500 1000 1500

) [p

b]

ττ

→Z’

(BR

×

) Z’

→pp

(σ

-310

-210

-110

1

ATLAS Preliminary-1

dt L = 4.6 fb∫ = 7 TeVs

(a)

µe

hτe /hτµ

hτhτ

comb.

Observed limitsExpected limits

SSMZ’

[GeV]Z’

m

500 1000 1500

) [p

b]

ττ

→Z’

(BR

×

) Z’

→pp

(σ

-310

-210

-110

1

ATLAS Preliminary-1

dt L = 4.6 fb∫ = 7 TeVs

Combined

(b) Expected limit

σ 1±Expected

σ 2±Expected

Observed limit

SSMZ’

Combined limit

34

• τhτh: 1.25 (1.35) TeV

• µτh: 1.06 (1.05) TeV

• eτh: 1.10 (1.02) TeV

• eµ: 0.73 (0.79) TeV(BAT Bayesian limit)

Z’ SSM Exclusions: observed (expected) @ 95% CL

Ryan Reece (Penn)

Final mass plots

35

) [GeV]missTE, hτ, hτ(

totTm

0 500 1000 1500

Events

/ 5

0 G

eV

-210

-110

1

10

210

310

410

ATLAS Preliminary-1

dt L = 4.6 fb∫ = 7 TeVs

(a)Data 2011

Multijetττ→*γ/Z

ντ→W

Others

ττ→(1250)Z’

) [GeV]missTE, hτ, µ(tot

Tm

0 500 1000 1500

Events

/ 5

0 G

eV

-210

-110

1

10

210

310

410ATLAS Preliminary

-1dt L = 4.6 fb∫ = 7 TeVs

(b)Data 2011

ττ→*γ/Z

+jetsW

Multijet

µµ→Z

tt

Dibosonsingle top

ττ→(1000)Z’

) [GeV]missTE, hτ, e(

totTm

0 500 1000 1500

Events

/ 5

0 G

eV

-210

-110

1

10

210

310

410ATLAS Preliminary

-1dt L = 4.6 fb∫ = 7 TeVs

(c)Data 2011

ττ→*γ/Z

+jetsZ/W

Multijet

ee→Z

tt

Dibosonsingle top

ττ→(1000)Z’

) [GeV]missTE, µ, e(tot

Tm

0 500 1000 1500

Events

/ 5

0 G

eV

-210

-110

1

10

210

310

410ATLAS Preliminary

-1dt L = 4.6 fb∫ = 7 TeVs

(d)Data 2011

Dibosonττ→*γ/Z

tt+jetsW

µµ→Zττ→(750)Z’

Ryan Reece (Penn)

Conclusions

36

• The analysis of the eτh channel has been completed

and combined with the previous three channels.

• The other three channels have only had minor updates.

• The combined limit on SSM Z’ has increased from 1.3

(1.4) to 1.4 (1.4) TeV, observed (expected).

• We are competitive with CMS, who published the limit

of 1.4 (1.1) TeV

http://arxiv.org/abs/1206.1725

• We have a publication first draft under the review of

our ed-board.

Ryan Reece (Penn)

Documents

• Supporting document

ATL-COM-PHYS-2012-394

https://cdsweb.cern.ch/record/1439018

• ICHEP 2012 Conference note

ATLAS-CONF-2012-067

https://cdsweb.cern.ch/record/1460263

• Publication draft for PLB to be reviewed by ATLAS

ATL-COM-PHYS-2012-1216

https://cdsweb.cern.ch/record/1472945/

37

Back up

Ryan Reece (Penn)

Summary tables

39

Uncertainty [%] Signal Background(τhτh / µτh / eτh / eµ)

Stat. uncertainty 1 / 2 / 2 / 3 5 / 20 / 23 / 7Eff. and fake rate 16 / 10 / 8 / 1 12 / 16 / 4 / 3Energy scale and res. 5 / 7 / 6 / 2 +22

−11 / 3 / 8 / 5Theory cross section – / – / – / – 9 / 4 / 4 / 5Luminosity 2 / 2 / 2 / 2 1 / 1 / 1 / 2Data-driven methods – / – / – / – +21

−11 / 6 / 16 / –

Table 2: Uncertainties on the estimated signal and total back-

ground contributions in percent for each channel. The following sig-

nal masses are used: 1250 GeV for τhτh; 1000 GeV for µτh and eτh;

and 750 GeV for eµ. A dash denotes that the uncertainty is not ap-

plicable. The statistical uncertainty corresponds to the uncertainty

due to limited sample size of the MC and control regions.

Ryan Reece (Penn)

Summary tables

40

τhτh µτh eτh eµZ/γ∗

→ ττ 0.73±0.23 0.36±0.06 0.6±0.1 0.55±0.07W+jets 0 0.3±0.2 0.8±0.4 0.33±0.10Z(→ ℓℓ)+jets 0 0 0 0.06±0.02tt̄ 0 0.33±0.15 0.13±0.09 1.0±0.2Diboson 0 0.23±0.07 0.06±0.03 1.7±0.2Single top 0 0.2±0.2 0 0Multijet 0.24±0.15 0 0 0Total expected background 1.0±0.3 1.4±0.4 1.6±0.5 3.6±0.4Events observed 2 1 0 5Expected signal events 6.3±1.1 5.5±0.7 5.0±0.5 6.7±0.3Signal efficiency (%) 4.3 1.1 1.0 0.4

Table 3: Number of expected and observed events in selected signal regions for each analysis channel. The expected contribution from the

signal in each channel is calculated for the mass point closest to the Z′

SSMexclusion limit: 1250 GeV for τhτh; 1000 GeV for µτh and eτh;

and 750 GeV for eµ. The signal regions corresponding to these mass points are used. The total uncertainties on each estimated contribution

are shown. The signal efficiency denotes the expected number of signal events divided by the product of the Z′

SSMcross section and the

integrated luminosity.

Ryan Reece (Penn)

Log-x binning

41

Events

-110

1

10

210

310

410

510 data 2011

τ τ →Z W+jets

multijet

µ µ →Z

tt dibosonsingle top

syst.⊕stat.

Z’(750)

Z’(1000)

Z’(1250)

ATLAS Internal-1dt L = 4.6 fb∫

) [GeV]miss

T, E

hτ, µ(TM

2103

10

obs.

/ exp.

0

1

2

Events

-110

1

10

210

310

410 data 2011

τ τ →Z W/Z+jets

multijet

e e→Z

tt γW

dibosonsingle top

syst.⊕stat.

Z’(750)

Z’(1000)

Z’(1250)

ATLAS Internal-1dt L = 4.6 fb∫

) [GeV]miss

T, E

hτ(e, TM

2103

10

obs.

/ exp.

0

1

2

eτh channelµτh channel

Ryan Reece (Penn)

pT(e)

42

Ele

ctr

ons /

(5 G

eV

)

0

50

100

data 2011

τ τ →Z W/Z+jets

multijet

e e→Z

tt γW

dibosonsingle top

syst.⊕stat.

Z’(750)

Z’(1000)

Z’(1250)

ATLAS Internal-1dt L = 4.6 fb∫

(e) [GeV]T

p

0 20 40 60 80 100 120 140obs.

/ exp.

0

1

2

Events

/ (

20 G

eV

)

-110

1

10

210

310

410data 2011

τ τ →Z W/Z+jets

multijet

e e→Z

tt γW

dibosonsingle top

syst.⊕stat.

Z’(750)

Z’(1000)

Z’(1250)

ATLAS Internal-1dt L = 4.6 fb∫

(e) [GeV]T

p

0 100 200 300 400 500 600obs.

/ exp.

0

1

2

Figure 23: The distribution of the transverse momentum of the selected electron. These plots include the

requirements of: exactly one selected electron, no additional preselected electrons or muons,

exactly one selected 1-prong tau, |∆φ(e, τh)| > 2.7, opposite sign e and τh, EmissT> 30 GeV,

and mT(e, EmissT) < 50 GeV.

Ryan Reece (Penn)

pT(τh)

43

Ta

u C

an

did

ate

s / (

5 G

eV

)

0

20

40

60

80 data 2011

τ τ →Z W/Z+jets

multijet

e e→Z

tt γW

dibosonsingle top

syst.⊕stat.

Z’(750)

Z’(1000)

Z’(1250)

ATLAS Internal-1dt L = 4.6 fb∫

) [GeV]hτ(

Tp

0 20 40 60 80 100 120 140obs.

/ exp.

0

1

2

Events

/ (

20 G

eV

)

-110

1

10

210

310

410data 2011

τ τ →Z W/Z+jets

multijet

e e→Z

tt γW

dibosonsingle top

syst.⊕stat.

Z’(750)

Z’(1000)

Z’(1250)

ATLAS Internal-1dt L = 4.6 fb∫

) [GeV]hτ(

Tp

0 100 200 300 400 500 600obs.

/ exp.

0

1

2

Figure 24: The distribution of the transverse momentum of the selected hadronic tau. These plots

include the requirements of: exactly one selected electron, no additional preselected elec-

trons or muons, exactly one selected 1-prong tau, |∆φ(e, τh)| > 2.7, opposite sign e and τh,

EmissT> 30 GeV, and mT(e, E

missT) < 50 GeV.

Ryan Reece (Penn)

Fake factors more quark-like at high-pT

44

Tau C

andid

ate

s / (

5 G

eV

)

0

20

40

60

80 data 2011

! ! "Z

h!fake

e e"Z

tt #W

dibosonsingle top

syst.$stat.

Z’(750)

Z’(1000)

Z’(1250)

ATLAS Internal-1dt L = 4.6 fb%

) [GeV]h!(

Tp

0 20 40 60 80 100 120 140obs.

/ exp.

0

1

2

Events

/ (

10 G

eV

)

0

10

20

30 data 2011

! ! "Z

h!fake

e e"Z

tt #W

dibosonsingle top

syst.$stat.

Z’(750)

Z’(1000)

Z’(1250)

ATLAS Internal-1dt L = 4.6 fb%

Blin

ded

) [GeV]h!(

Tp

100 150 200 250 300obs.

/ exp.

0

1

2

• Because the quark-fraction increases with pT, the single

fake factor method agrees better at high-pT.

Ryan Reece (Penn)

Events

/ (

10 G

eV

)

0

50

100

data 2011

! ! "Z

h!fake

e e"Z

tt #W

dibosonsingle top

syst.$stat.

Z’(750)

Z’(1000)

Z’(1250)

ATLAS Internal-1dt L = 4.6 fb%

) [GeV]miss

T(e, ETm

0 20 40 60 80 100 120140 160 180 200obs.

/ exp.

0

1

2

Cross-check: single fake factor method

45

Events

/ (

10 G

eV

)

0

50

100

data 2011

! ! "Z W/Z+jets

multijet

e e"Z

tt #W

dibosonsingle top

syst.$stat.

Z’(750)

Z’(1000)

Z’(1250)

ATLAS Internal-1dt L = 4.6 fb%

) [GeV]miss

T(e, ETm

0 20 40 60 80 100 120140 160 180 200obs.

/ exp.

0

1

2

• as expected, the single fake factor method over-

estimates in regions where the multijet contamination

is large

double fake factor single fake factor

Ryan Reece (Penn)

Object preselection

46

Muons

StoreGate key: StacoMuonCollection

Tau D3PD prefix: mu staco *

pT > 10 GeV

|η| < 2.5

mu staco loose == 1

Require a B-layer hit if expected (expectBLayerHit == 0 or nBLHits > 0)

N(pixel hits) + N(pixel dead) ≥ 2

N(SCT hits) + N(SCT dead) ≥ 6

N(pixel holes) + N(SCT holes) ≤ 2

TRT quality cuts:if abs(eta) < 1.9:

if not ( (nTRTHits + nTRTOutliers > 5) and \

(nTRTOutliers < 0.9*(nTRTHits + nTRTOutliers))):

return False

elif (nTRTHits + nTRTOutliers > 5):

if not (nTRTOutliers < 0.9*(nTRTHits + nTRTOutliers)):

return False

return True

Electrons

Tau D3PD prefix: el *

pT > 15 GeV

(|η| < 1.37) or (1.52 < |η| < 2.47)

el author in (1, 3)

el mediumPP == 1

Require a B-layer hit if expected (expectBLayerHit == 0 or nBLHits > 0)

Taus

Ryan Reece (Penn)

Object preselection

47

Require a B-layer hit if expected ( )

Taus

StoreGate key: TauRecContainer

Tau D3PD prefix: tau *

pT > 25 GeV

(|η| < 1.37) or (1.52 < |η| < 2.47)

tau author in (1, 3)

tau numTrack > 0

Remove candidates overlapping with preselected electrons or muons within ∆R < 0.2

Jets

StoreGate key: AntiKt4LCTopoJets

Tau D3PD prefix: jet *

pT > 25 GeV

|η| < 4.5

|JVF| > 0.75 for jets with |η| < 2.4

Remove candidates overlapping with preselected electrons or selected taus within ∆R < 0.2

Ryan Reece (Penn)

Fake factors

48

Electron isolation Tau identification

(e) [GeV]T

p

0 50 100 150 200 250 300 350 400

: m

ultije

te-iso

f

0

0.2

0.4

0.6

0.8

1

1.2

1.4Inclusive

Barrel

Endcap

ATLAS Internal

) [GeV]h!(

Tp

0 50 100 150 200 250

)h!

)+je

ts,

OS

(e,

" e

#

: W

(!

f

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

Inclusive

Barrel (inner)

Barrel (outer)

Endcap

ATLAS Internal

Ryan Reece (Penn)

Electron isolation

49

•

corrected etcone20/pT < 5% if pT < 100 GeV

corrected etcone20 < 5 GeV if pT > 100 GeV,

• ptcone40/pT < 5%,

•

corrected etcone20/pT > 8% if pT < 100 GeV

corrected etcone20 > 8 GeV if pT > 100 GeV,

• or ptcone40/pT > 6%.

isolated anti-isolated

track isolation calorimeter isolation

Gap between isolated and anti-isolated makes

data-driven multijet more pure (less corrected)

Tptcone40 / p

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5

Ele

ctr

ons /

0.0

1

-110

1

10

210

310

410

510

610

710data 2011

! ! "Z

# e "W

# ! "W

e e"Z

tt

$W

diboson

single top

syst.%stat.

Z’(750)

Z’(1000)

Z’(1250)

ATLAS Internal -1dt L = 4.6 fb&

Tcorrected Etcone20 / p

-0.1 0 0.1 0.2 0.3 0.4 0.5

Ele

ctr

ons /

0.0

1

-110

1

10

210

310

410

510

610 data 2011

! ! "Z

# e "W

# ! "W

e e"Z

tt

$W

diboson

single top

syst.%stat.

Z’(750)

Z’(1000)

Z’(1250)

ATLAS Internal -1dt L = 4.6 fb&

Ryan Reece (Penn)

Electron veto

50

• above are the scale factors

and errors for the

EleBDTMedium e-veto

• These SF have huge ≈100%

uncertainties, and we’ve also

previously shown that this

veto is inefficient at high pT.

) [GeV]hτ(truth

Tp

0 100 200 300 400 500 600

effic

ien

cy

0

0.2

0.4

0.6

0.8

1

EleBDTLoose

EleBDTMedium

EleBDTTight

MuonVeto

ATLAS Internal

|η| < 1.37 1.37 < |η| < 1.52 1.52 < |η| < 2.0 2.0 < |η|

BDT medium e-veto 1.64(0.81) 1.0(1.0) 0.71(0.63) 2.90(1.42)

BDT loose e-veto 1.21(0.30) 0.96(0.46) 0.59(0.21) 1.76(0.55)

Ryan Reece (Penn)

Multijets background

51

• Loosened tau ID requirement

in the anti-isolated lepton +

tau data sample used to

model the multijet

background.

• Sample with tau ID is already

multijet dominated.

Loosening tau ID improves

stats.

• Shapes are statistically

consistent. Inclusive shape

scaled to the prediction with

medium tau ID to give the

estimate in the tail.

) [GeV]miss

T, Ehτ(e, TM

0 200 400 600 800 1000 1200 1400

Events

/ (

50 G

eV

)-310

-210

-110

1

10

210

310

410

510

610

JetBDTSigMedium

JetBDTSigLoose

Inclusive

SM background

multijetATLAS Internal -1dt L = 4.6 fb∫

Ryan Reece (Penn)

Z → ee + jets background

52

• Categorize Monte Carlo events by electron or jet faking tau.

• Loosen electron veto in Monte Carlo sample matched to electron fakes.

• Shapes are consistent, and only driven by the Z → ee kinematics.

• Z → ee with e-faking tau is negligible

• Z → ee + jet-fake covered with the data-driven W/Z+jet tau fake factor method.

) [GeV]miss

T, Ehτ(e, TM

0 200 400 600 800 1000 1200 1400

Events

/ (

20 G

eV

)

-310

-210

-110

1

10

210

310

410

510

610

e e-fake→Z

e e + jet-fake→Z

SM background

e e→Z ATLAS Internal -1dt L = 4.6 fb∫

) [GeV]miss

T, Ehτ(e, TM

0 200 400 600 800 1000 1200 1400

Events

/ (

20 G

eV

)

-310

-210

-110

1

10

210

310

410

510

610

EleBDTMedium

EleBDTLoose

BDTEleScore > 0.3

SM background

e e→Z ATLAS Internal -1dt L = 4.6 fb∫

Ryan Reece (Penn)

High-pT tau efficiency systematic

53

) [GeV]τ(probe-T

p

0 200 400 600 800 1000

Scale

Facto

r

0

0.2

0.4

0.6

0.8

1

1.2

1.4 / ndf 2χ 4.2 / 6

p0 0.05± 0.81

p1 0.00016± 0.00015

/ ndf 2χ 4.2 / 6

p0 0.05± 0.81

p1 0.00016± 0.00015

/ ndf 2χ 4.2 / 6

p0 0.05± 0.81

p1 0.00016± 0.00015

BDT60• The dominant systematic uncertainty for

the Z’ signal and the Z→ττ background.

• Low pT uncertainty of 4% taken from the

Tau WG blessed Z→ττ tag-and-probe.

• No high-pT control sample of true taus.

• Assume mis-modeling comes from either:

1. tau kinematics (TAUOLA)

2. detector response to high-pT pions←dominant

• Instead of using true taus, measure the trend in the scale

factor for fakes from dijet events.

• pT ≤ 100 GeV: ∆ε = 4% (taken from the Z → ττ measurement)

• pT > 100 GeV: ∆ε = 4+ 0.016(pT − 100)%, with pT in GeV (taken from the dijets measurement).

Ryan Reece (Penn)

Summary of µτh/eτh channel differences

54

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)

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! ! "Z W/Z+jets

multijet

e e"Z

tt #W

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e e"Z

tt #W

dibosonsingle top

syst.$stat.

Z’(750)

Z’(1000)

Z’(1250)

ATLAS Internal-1dt L = 4.6 fb%

) [GeV]miss

T(e, ETm

0 20 40 60 80 100 120140 160 180 200obs.

/ exp.

0

1

2

after MET > 30 GeV and OS

• electron isolation:

• etcone20 / pt < 5% if pt < 100 GeV else etcone20 < 5 GeV

• ptcone40 < 5%

• MET > 30 GeV

• mT(e,MET) < 50 GeV

To further suppress multijet

and Z→ee backgrounds.

Ryan Reece (Penn)

µτh cut-flow

55

data total SM Z → ττ W+jets multijet Z → µµ t t diboson single top Z′(1000)

one µ, one τh 11605 11653(47) 3867(35) 4913(21) 583(5) 897(21) 963(7) 323(4) 108(3) 18.7(2)

|∆φ(µ, τh)| > 2.7 6061 5941(38) 2829(31) 1811(14) 403(4) 533(17) 221(3) 117(2) 27(1) 17.9(2)

opposite sign µ and τh 5320 5242(37) 2791(31) 1446(13) 213(3) 452(16) 208(3) 107(2) 24(1) 17.6(2)

MT > 200 GeV 229 263(5) 30.0(5) 114(4) 5.5(4) 5(1) 76(2) 22.3(8) 9.4(9) 16.5(2)

MT > 300 GeV 31 53(2) 7.3(2) 18(2) 0.6(1) 0.3(2) 17.6(9) 6.7(6) 3.0(5) 14.1(2)

MT > 400 GeV 13 15(1) 2.31(5) 5.0(8) 0.15(7) 0.1(1) 4.5(4) 1.7(2) 0.9(3) 11.0(2)

MT > 500 GeV 1 4.5(5) 0.82(3) 1.6(5) 0.02(2) < 0.1 1.2(2) 0.6(1) 0.3(2) 8.0(1)

MT > 600 GeV 1 1.4(3) 0.36(2) 0.3(2) < 0.01 0.3(1) 0.23(7) 0.2(1) 5.5(1)

MT > 700 GeV 1 0.5(1) 0.17(1) 0.07(7) 0.03(3) 0.13(5) 0.1(1) 3.38(9)

Ryan Reece (Penn)

µτh systematics

56

W+jets Z → ττ t t diboson single top Z′(1000)

expected events 0.3 0.4 0.3 0.2 0.2 5.5

total. uncert. 77 18 46 33 95 13

stat. uncert. 71 5 35 29 74 2

syst. uncert. 30 17 30 15 59 12

µ efficiency - 0 0 0 0 2

µ pT resolution ID - 0 0 2 0 2

µ pT resolution MS - 0 0 1 0 2

τh efficiency - 6 5 5 0 10

jet→ τh fake rate - 0 11 0 0 0

e→ τh fake rate - 0 25 11 58 0

jet energy scale - 11 2 2 0 6

jet energy resolution - 1 0 2 0 2

cluster energy scale - 0 1 2 0 2

luminosity - 2 2 2 2 2

theo. cross section - 11 10 7 13 -

τh fake factor 30 - - - - -

• statistics

• e→τh SF

• fake factor on

W+jets

(uncertainties in %)

[GeV]Z’

m

500 1000 1500

) [p

b]

!!

"Z’

(BR

!

) Z’

"pp

(#

-310

-210

-110

1

ATLAS Preliminary-1

dt L = 4.6 fb$ = 7 TeVs

channelh!h!

Expected limit

# 1"Expected

# 2"Expected

Observed limit

SSMZ’

[GeV]Z’

m

500 1000 1500

) [p

b]

!!

"Z’

(BR

!

) Z’

"pp

(#

-310

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dt L = 4.6 fb$ = 7 TeVs

channelh!h!

Expected limit

# 1"Expected

# 2"Expected

Observed limit

SSMZ’

95% mu upper limit0 2 4 6 8 10 12 14 16 18 20

0

2

4

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8

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MuUpper95CLhlow_mu_UL

Entries 1000Mean 4.946

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0

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400

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MuUpper95CLhmed_mu_UL

Entries 5000Mean 4.985

RMS 1.59

MuUpper95CL

Running bands at high precision• Band Calculation:

• Generate pseudo-data by randomly sampling ‘N observed’ from background only model

• For each ‘N observed’ calculate the upper limit on the signal strength

• The quantiles of the resulting distribution for the mu upper limit give you the median and ±1σ ±2σ bands

• Until now, was running mu upper limit calculation at low precision for the bands to save time, which artificially broadens the peaks in the output distribution

• Running at high precision can cause the -1σ and -2σ bands to overlap for low expected bkg.

57

pseudo N Observed0 1 2 3 4 5 6 7 8 9 10

95%

mu u

pper

limit

0

2

4

6

8

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12

14

16

18

20

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Entries 1000Mean x 1.039Mean y 4.946

RMS x 1.047RMS y 1.588

MuUpper95CL:NObs

pseudo N Observed0 1 2 3 4 5 6 7 8 9 10

95%

mu u

pper

limit

0

2

4

6

8

10

12

14

16

18

20

MuUpper95CL:NObshmed_mu_UL_nobs

Entries 5000Mean x 1.064Mean y 4.985

RMS x 1.066RMS y 1.59

MuUpper95CL:NObs

Low Precision High Precision

mZ’=1750 GeVmZ’=1750 GeV

mZ’=1750 GeVmZ’=1750 GeV

[GeV]Z’

m

500 1000 1500

) [p

b]

!!

"Z’

(BR

!

) Z’

"pp

(#

-310

-210

-110

1

ATLAS Preliminary-1

dt L = 4.6 fb$ = 7 TeVs

channelh!h!

Expected limit

# 1"Expected

# 2"Expected

Observed limit

SSMZ’

[GeV]Z’

m

500 1000 1500

) [p

b]

!!

"Z’

(BR

!

) Z’

"pp

(#

-310

-210

-110

1

ATLAS Preliminary-1

dt L = 4.6 fb$ = 7 TeVs

channelh!h!

Expected limit

# 1"Expected

# 2"Expected

Observed limit

SSMZ’

95% mu upper limit0 2 4 6 8 10 12 14 16 18 20

0

2

4

6

8

10

12

14

16

18

MuUpper95CLhlow_mu_UL

Entries 1000Mean 4.946

RMS 1.588

MuUpper95CL

95% mu upper limit0 2 4 6 8 10 12 14 16 18 20

0

100

200

300

400

500

600

MuUpper95CLhmed_mu_UL

Entries 5000Mean 4.985

RMS 1.59

MuUpper95CL

Running bands at high precision• Band Calculation:

• Generate pseudo-data by randomly sampling ‘N observed’ from background only model

• For each ‘N observed’ calculate the upper limit on the signal strength

• The quantiles of the resulting distribution for the mu upper limit give you the median and ±1σ ±2σ bands

• Until now, was running mu upper limit calculation at low precision for the bands to save time, which artificially broadens the peaks in the output distribution

• Running at high precision can cause the -1σ and -2σ bands to overlap for low expected bkg.

58

pseudo N Observed0 1 2 3 4 5 6 7 8 9 10

95%

mu u

pper

limit

0

2

4

6

8

10

12

14

16

18

20

MuUpper95CL:NObshlow_mu_UL_nobs

Entries 1000Mean x 1.039Mean y 4.946

RMS x 1.047RMS y 1.588

MuUpper95CL:NObs

pseudo N Observed0 1 2 3 4 5 6 7 8 9 10

95%

mu u

pper

limit

0

2

4

6

8

10

12

14

16

18

20

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Entries 5000Mean x 1.064Mean y 4.985

RMS x 1.066RMS y 1.59

MuUpper95CL:NObs

Low Precision High Precision

-2σ-1σ+1σ

µ +2σ-2σ-1σ +1σ

µ

+2σ

mZ’=1750 GeVmZ’=1750 GeV

Recap of method1. Model multijet MT shape using same-sign

events:

• 99.2% multijet purity in SS events

• OS/SS shapes agree well (top figure)

• Fit with ‘dijet’ function (bottom figure):

• good χ2/NDF

• tail integral matches observed SS events well for any choice of MT threshold

• shape of high-mass tail verified using dijet MC enriched in high-mass events

• statistical uncertainty 10-40% depending on MT threshold used in signal region, determined using pseudo-experiments

• only model down to 160 GeV to avoid threshold effects (will come back to this)

59

Norm

aliz

ed e

vent

rate

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0.15

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0.25

0.3

ATLAS Preliminary-1

dt L = 4.7 fb! = 7 TeVs

Opposite Charge (OC)

Same Charge (SC)

) [GeV]missTE, h", h"(TM

200 250 300 350

OC

/ S

C

0.51

1.5

) [GeV]missTE, h

!, h!(TM

200 400 600 800 1000

Events

/ 2

0 G

eV

-210

-110

1

10

210

310 ATLAS Preliminary

-1dt L = 4.7 fb" = 7 TeVs

/ NDF: 9.43 / 132#

650) = 1$TM(DataN

650) = 0.5$TM(FitN

OS/SS shapes agree well

Recap of method

2. Normalise shape to data in low-mass side-band:

• 160 < MT < 200 GeV (first bin of MT plot)

• 6% contamination from other backgrounds subtracted

• negligible signal contamination for all signal mass hypotheses

• negligible statistical uncertainty

60

Events

/ 4

0 G

eV

-110

1

10

210

310

410ATLAS Preliminary

-1dt L = 4.7 fb! = 7 TeVs

Data 2011Multijet

""#*$/Z

%"#W

Others""#(1250)Z’

) [GeV]missTE, h", h"(TM

500 1000 1500obs.

/ exp.

0.51

1.5

Issue that was addressed for paper

• For the CONF there was no estimate of the systematic uncertainty due to the choice of the fitting function.

• This was a request during the CONF final approval, but there was not enough time to address it at that time

• The issue has been addressed for the paper.

61

Change 1

• Include a new systematic uncertainty that accounts for the choice of the fitting function

• Method: Find another function that models multijet events well, fit it to the SS data, and take the deviation of the estimate w.r.t the nominal fitting function as an additional uncertainty

• Crystal Ball chosen, as it was shown to model multijets well (see backup slides)

• Tail fractions in signal region 36% higher when fitting with CB function

62

[GeV]TM

0 200 400 600 800 1000 1200 1400 1600 1800 200010×

Events

-410

-310

-210

-110

1

10

210

310dijet function

crystal ball

Fit to SS region using nominal and alternate fit functions

high-mass counting region

Change 2

• Raise the minimum of the fitting range:

• The large discrepancy between the nominal and CB fit was unexpected because CB was shown to be an unbiased estimator of the tail-fraction using pseudo-experiments (see backup)

• After further investigation it turns out that the MT>160 GeV range used for the fit was not adequately avoiding the turn on region (see backup)

• Solution:

• raise the fit minimum to 200 GeV

63

[GeV]TM

0 200 400 600 800 100010!

Events

/ 2

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eV

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1

10

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310

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ATLAS Internal

QCD

Chi2/NDF: 7.60 / 11

700) = 0!(DataN

700) = 0.2!(FitN

old fit min too close to turn-on

region(not modelled by fitting functions)

new fit min

old fit min

Consequences of raising fit min

• Raising the fit minimum from 160 to 200 GeV has the following effects:

• reduces bias in the multijet estimate

• increases the statistical uncertainty of the fit

• the side-band must be shifted from [160,200] to [200,250], which means:

• increased statistical uncertainty from normalisation (now non-negligible)

• increased signal contamination for very low mass-points:

• as a result, the old fit range is still used for the two low-mass signal points because for these points there is non-negligible signal contamination in the 200-250 side-band

64

τhτh channel summary

• Lower bound of the fit range for the high-mass points was increased which gives a more unbiased central value for the multijet estimate.

• Included new systematic uncertainty to account for shape systematics.

• Despite taking further systematic effects into account, the multijet estimation doesn't vary much and it doesn't affect the limit.

65

Determining alternate fitting functions

Key: We only want to accept functions that accurately model dijets over the full MT range:

1. Fit dijet function to high-stat dijet MC

2. Generate high-stat pseudo-data from this model

3. Check which functions can model the pseudo-data over the full mass range

Only other suitable function: Crystal Ball

66

[GeV]TM

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Events

/ 1

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eV

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-110

1

10

210

310 10±a = 7

0.38±b = -0.548

ATLAS Internal

Simulation

Chi2/NDF = 379.1 / 157

MT

400 600 800 1000 1200 1400 1600 1800 200010!

Events

/ (

16000 )

-110

1

10

210

310

410

510 0.0059"acb = -0.26035

8021"mcb = 196780

0.070"ncb = 9.137

229"scb = 10093

sig frac: 0.00255

/NDF: 1.752!

ATLAS Internal

MT

400 600 800 1000 1200 1400 1600 1800 200010!

Events

/ (

16000 )

-110

1

10

210

310

410

510 77"ml = 418075

24"sl = 16763

sig frac: 0.023

/NDF: 2.21e+032!

ATLAS Internal

MT

400 600 800 1000 1200 1400 1600 1800 200010!

Events

/ (

16000 )

-110

1

10

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310

410

510 0.0055"a = -6.76913

sig frac: 0.00489

/NDF: 52.42!

ATLAS Internal

Step 1

Step 2 and 3

✔ ✖ ✖

Note: fit range of 400-2000 used to avoid region effected by pT thresholds

Fit range

many other models were also tried....

Low stats bias (Yann’s test)• Method:

• Generate pseudo-data from the di-jet function fitted to MC (top right figure previous slide)

• Refit it with di-jet function and Crystal Ball

• Perform pseudo-experiments in batches with decreasing numbers of events per trial to see if either di-jet or CB become biased with low stats in the tail

• Result: Both produce unbiased tail fractions

67

Number of events per trial

310 410

510

610

Ave

rag

e f

it f

ractio

n in

sig

na

l re

gio

n

0.001

0.0015

0.002

0.0025

0.003Nominal Tail Fraction

Number of events per trial

310 410

510

610

Ave

rag

e f

it f

ractio

n in

sig

na

l re

gio

n

0.0015

0.002

0.0025

0.003

0.0035

0.004 Nominal Tail Fraction

di-jet function Crystal Ball

Determining the best fitting range

• Increasing the minimum of the fit range has 2 main effects:

• estimates from nominal (dijet) function asymptote

• estimates from dijet and crystal ball converge

• These indicate that a choice of 200-250 would give the most unbiased estimates

• At the same time, the statistical uncertainty from the fit, and the uncertainty from the side-band normalisation also increases when increasing the minimum of the fit range, so 200 is the best choice

68

[GeV]TM

0 200 400 600 800 1000 1200 1400 1600 1800 200010×

Events

-410

-310

-210

-110

1

10

210

310dijet function

crystal ball

[GeV]TM

0 200 400 600 800 1000 1200 1400 1600 1800 200010×

Events

-410

-310

-210

-110

1

10

210

310dijet function

crystal ball

[GeV]TM

0 200 400 600 800 1000 1200 1400 1600 1800 200010×

Events

-410

-310

-210

-110

1

10

210

310dijet function

crystal ball

Min fit range dijet function crystal ball

MT>160 0.36 0.49

MT>180 0.32 0.40

MT>200 0.24 0.26

MT>250 0.23 0.23

Multijet estimates in MT>700 GeV signal region

Fitmin: 160 GeV

Fitmin: 200 GeV

Fitmin: 250 GeV

Ryan Reece (Penn)

pass/f

ail

0

0.05

0.1

W CR: Inclusive, 1p

W CR: OS, 1p

W CR: SS, 1p

Tp

0 50 100 150 200 250

ratio

0

1

2

pass/f

ail

0

0.05

0.1

QCD CR: Inclusive, 1p

QCD CR: OS, 1p

QCD CR: SS, 1p

Tp

0 50 100 150 200 250

ratio

0

1

2

BDT Medium BDT Medium

Observed variance in fake-rates

69

(BDTMedium)

1. Why do quarks and gluons have different tau fake-rates?

2. How does the quark/gluon fraction vary among samples?

• Hypothesis: quarks vs gluons

• Divide the issue into two questions:

Ryan Reece (Penn)

Jet width for quark/gluons

70

J. Gallicchio, M. Schwartz. “Quark and Gluon Tagging at the LHC”. arXiv:1106.3076.

• !(r) = fraction of jet

energy within ∆R < r.

• Quark jets are more

narrow than gluon jets

of the same energy.

• Tau identification prefers

narrow candidates.

• This is consistent with samples of quark-enriched jets, like

W+jet, having higher fake-rates.

Ryan Reece (Penn)

OS vs SS W+jet

71

q

Wg

q′

(a)

q W

g q′

(b)

q

q̄′W

g

(c)

• The charge of the quark should correlate with the

reconstructed charge of the tau candidate, therefore (a) and

(b) preferably produce opposite sign W+jet events.

• OS and SS will have different quark/gluon fractions.

Leading order W+jet production:

Ryan Reece (Penn)

Madgraph predicted Quark/Gluon

72

50 100 200 400 800 1600

Q

G

0%

100%

80%

60%

40%

20%

pT Cut on All Jets (GeV)50 100 200 400 800 1600

Q

G

0%

100%

80%

60%

40%

20%

pT Cut on All Jets (GeV)

J. Gallicchio, M. Schwartz. “Pure Samples of Quark and Gluon Jets at the LHC”. arXiv:1104.1175

50 100 200 400 800 16000%

100%

80%

60%

40%

20%

GG

QG

QQ

pT Cut on All Jets (GeV)50 100 200 400 800 1600

0%

100%

80%

60%

40%

20%

GGG

QGG

QQG

QQQ

pT Cut on All Jets (GeV)

Ryan Reece (Penn)

W+jets fake factor systematic

73

) [GeV]hτ(

Tp

0 50 100 150 200 250

τ f

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

)+jetν l →W(

)+jetµµ →Z(

ee)+jet→Z(

) [GeV]hτ(

Tp

0 50 100 150 200 250

τ f

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

)hτ)+jet, OS(l, ν l →W(

)+jetµµ →Z(

ee)+jet→Z(

Figure 44: (left) Tau identification fake factors taken from regions of data enriched in W(→ ℓν)+jets,

Z(→ µµ)+jets, and Z(→ ee)+jets events. The fake factors are consistent within statistical

errors among samples. (right) Tau identification fake factors taken from regions of data

enriched inW(→ ℓν)+jets, Z(→ µµ)+jets, and Z(→ ee)+jets events, where the lepton and jet

are restricted to have opposite signs in the W-rich regions. The fake factors differ by ≈ 20%

at low hadronic tau transverse momentum.

Ryan Reece (Penn)

Cross-check: single fake factor method

74

!"#$%%&'()%!*+!% ,-./.(0%1''#234% 5'2#0%603070!!!!!!"!

&)&%8'-.9#%03:%-;-#'10#2<-%

3-prong

ATLAS work in progress

0jet bin

Fake !"#$%&'("

comes from

quark.

Systematic uncertainty - Conservative way

!Up : F.F in W+0jet events.

!Down: F.F in multi-jets events.

MMC

+50%

-50%

Assign !50% to bkg. Normalization!

Ryan Reece (Penn)

Reminder of previous eτh issues

75

Ele

ctr

ons /

(5 G

eV

)

0

200

400

600

800data 2011

τ τ →Z W/Z+jets

multijet

e e→Z

tt γW

dibosonsingle top

Z’(750)

Z’(1000)

Z’(1250)

ATLAS Internal-1dt L = 4.6 fb∫

Blin

ded

(e) [GeV]T

p

0 20 40 60 80 100 120 140obs.

/ exp.

0

1

2 data stat. uncert.

model stat. uncert.

Ele

ctr

ons /

(10 G

eV

)

-110

1

10

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310

410

510data 2011

τ τ →Z W/Z+jets

multijet

e e→Z

tt γW

dibosonsingle top

Z’(750)

Z’(1000)

Z’(1250)

ATLAS Internal-1dt L = 4.6 fb∫

Blin

ded

(e) [GeV]T

p

0 100 200 300 400 500 600obs.

/ exp.

0

1

2 data stat. uncert.

model stat. uncert.

• Reminder: our e-had channel has been delayed because of the following

issues with the modeling:

• High pT(e) over-estimated; W+jet over-estimated; ruins signal region

• General lack of confidence in the Z → ee normalization; no real effect on signal region

• Last few weeks our general strategy has been to illustrate the systematics to try to cover

the discrepancy, varying electron isolation, and re-binning both the fake factors and

kinematic distributions.

Ryan Reece (Penn)

) [GeV]miss

T, Eh!(e, TM

210 310

Events

/ (

10 G

eV

)

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1

10

210

310

410data 2011

! ! "Z

multijet

e e"Z

tt

#W

diboson

single top

syst.$stat.

ATLAS Internal -1dt L = 4.6 fb%

(e) [GeV]T

p

210

Events

/ (

10 G

eV

)

-110

1

10

210

310

410data 2011

! ! "Z

multijet

e e"Z

tt

#W

diboson

single top

syst.$stat.

ATLAS Internal -1dt L = 4.6 fb%

Failing tau ID control region

• Our understanding of what was wrong with the modeling is that

the multijet contamination is underestimated in the failing tau ID

control region, therefore causing the W+jet to be overestimated.

• Subtraction in the highest unblinded pT bin is ≈ 30%!

76

(used to estimate W+jet after subtraction)

Ryan Reece (Penn)

[GeV]missTE

0 20 40 60 80 100 120 140

Events

/ (

5 G

eV

)

0

50

100

150

200

250

300data 2011

! ! "Z

multijet

e e"Z

tt

#W

diboson

single top

syst.$stat.

ATLAS Internal -1dt L = 4.6 fb%

[GeV]missTE

210

Events

/ (

10 G

eV

)

-110

1

10

210

310

410data 2011

! ! "Z

multijet

e e"Z

tt

#W

diboson

single top

syst.$stat.

ATLAS Internal -1dt L = 4.6 fb%

Failing tau ID control region

• To help decouple the multijet and W+jet estimates, we added a

MET cut back to the event selection.

• The new/current selection requires MET > 30 GeV.

• This lessens the multijet contamination that needs to be

subtracted, improving the precision of the W+jet estimate.77

(used to estimate W+jet after subtraction)

Ryan Reece (Penn)

Events

/ (

10 G

eV

)

0

50

100

data 2011

! ! "Z W/Z+jets

multijet

e e"Z

tt #W

dibosonsingle top

syst.$stat.

Z’(750)

Z’(1000)

Z’(1250)

ATLAS Internal-1dt L = 4.6 fb%

) [GeV]miss

T(e, ETm

0 20 40 60 80 100 120140 160 180 200obs.

/ exp.

0

1

2

Events

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20 G

eV

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410 data 2011

! ! "Z W/Z+jets

multijet

e e"Z

tt #W

dibosonsingle top

syst.$stat.

Z’(750)

Z’(1000)

Z’(1250)

ATLAS Internal-1dt L = 4.6 fb%

) [GeV]miss

T(e, ETm

0 100200 300 400 500 600700 800 9001000obs.

/ exp.

0

1

2

Adding mT(e,MET) cut

• Many months ago we debated about using mT(e,MET) or ∆!(e,MET) cuts for rejecting

W+jets, but decided instead to use a simpler / more signal inclusive selection to not

reject signal where the MET is aligned with the hadronic tau.

• We propose adding a mT(e,MET) < 50 GeV cut, to suppress W+jet.

• This will make the W+jets modeling less important (and suppress ttbar), increasing the

purity of our irreducible Z→ττ background and simplifying our background composition.

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