Measurements of the top quark mass with the ATLAS...

24
Measurements of the top quark mass with the ATLAS detector p p t b b-jet W + ν + t b b-jet W ν [GeV] reco lb m 40 60 80 100 120 140 160 Events / 2 GeV 0 100 200 300 400 500 Data 1% background Best fit Uncertainty ATLAS -1 =8 TeV, 20.2 fb s EPS 2017 Conference Venice, July 7, 2017 Richard Nisius (MPP M ¨ unchen) for the ATLAS Collaboration

Transcript of Measurements of the top quark mass with the ATLAS...

Page 1: Measurements of the top quark mass with the ATLAS detectornisius/talks/VENE070717/Talk.pdfMeasurements of the top quark mass with the ATLAS detector t pp b ... 1 1.1 1.2 1.3 Scale

Measurements of the top quark masswith the ATLAS detector

p ptb

b-jet

W+

ν�

�+

t

b

b-jet

W−

�−ν�

[GeV]recolbm

40 60 80 100 120 140 160

Eve

nts

/ 2 G

eV

0

100

200

300

400

500 Data1% backgroundBest fitUncertainty

ATLAS-1=8 TeV, 20.2 fbs

ATLAS measurements of the top quark mass Richard Nisius (MPP Munchen) Venice, July 6, 2017 2 /2

EPS 2017 ConferenceVenice, July 7, 2017

Richard Nisius (MPP Munchen)for the ATLAS Collaboration

Page 2: Measurements of the top quark mass with the ATLAS detectornisius/talks/VENE070717/Talk.pdfMeasurements of the top quark mass with the ATLAS detector t pp b ... 1 1.1 1.2 1.3 Scale

Introduction Indirect determination Direct measurements Combination Conclusions Backup

The plan of this presentation

fg/p

fg/p

σgg→tt

τ+τ 1%

τ+µ 2%

τ+e 2%

µ+µ 1%

µ+e 2%

e+e 1%

e+jets 15%

µ+jets 15%

τ+jets 15%

"jets" 46%

"lepton+jets""dilepton" Introduction

[GeV]µe

TDilepton p

0 50 100 150 200 250 300

pred

ictio

n / d

ata

0.7

0.8

0.9

1

1.1

1.2

1.3

ScalePDFAlphaS

Data uncertainty

MCFM+HERAPDF 1.5

ATLAS Preliminary-1 = 8 TeV, 20.2 fbs

Indirect determination of mpoletop

− Lepton differential distributions, ATLAS-CONF-2017-044

[GeV]recolbm

50 100 150

Nor

mal

ised

eve

nts

/ 5

GeV

0.05

0.1

topm167.5 GeV172.5 GeV177.5 GeV

ATLASSimulation

[GeV]recolbm

40 60 80 100 120 140 160

Rat

io

0.60.8

11.21.4

Direct measurements of mtop

− All-jets channel, arXiv:1702.07546

− Lepton + jets channel, Eur. Phys. J. C75 (2015) 330

− Dilepton channel, Phys. Lett. B761 (2016) 350

[GeV]topm165 170 175 180 185

1

17

0.70± 172.84 Phys. Lett. B761 (2016) 350 ATLAS Comb. June 2016

-1 =4.6 fbintL

JHEP 10 (2015) 121+1-jet) t(tσ 2.1 2.3 ±173.7

-1 =4.6-20.3 fbintL

Eur. Phys. J. C74 (2014) 3109) dilepton t(tσ 2.6 2.5 ±172.9

-1 = 20.2 fbintLarXiv:1702.07546all jets 1.0 )± ( 0.6 1.2 ±173.7

-1 = 20.2 fbintL

Phys. Lett. B761 (2016) 350 dilepton → 0.7 )± ( 0.4 0.8 ±173.0

-1 = 4.7 fbintL

Eur. Phys. J. C75 (2015) 330 dilepton → 1.3 )± ( 0.5 1.4 ±173.8

-1 = 4.7 fbintL

Eur. Phys. J. C75 (2015) 330 l+jets → 1.0 )± 0.7 ± 0.2 ± ( 0.2 1.3 ±172.3

-1 =20.3 fbintLCONF-2014-055single top* 2.0 )± ( 0.7 2.1 ±172.2

-1 = 4.6 fbintL

Eur. Phys. J. C75 (2015) 158all jets 1.2 )± ( 1.4 1.8 ±175.1

-1 - 20.3 fb-1 = 4.6 fbint

summary - May 2017, Ltopm

syst.)± bJSF ± JSF ± tot. (stat. ± top m

σ 1 ±ATLAS Comb. stat. uncertainty

bJSF uncertainty⊕ JSF ⊕stat. total uncertainty

Input to comb.→Preliminary, *

ATLAS Preliminary

Combination of direct measurements

Conclusions

����H

HHH

Note: - I cannot discuss in detail all displayed content, however, the main result

figures have hyperlinks to the web page of the corresponding document.

Measurements of the top quark mass with ATLAS Richard Nisius (MPP Munchen) Venice, July 7, 2017 2 /24

Page 3: Measurements of the top quark mass with the ATLAS detectornisius/talks/VENE070717/Talk.pdfMeasurements of the top quark mass with the ATLAS detector t pp b ... 1 1.1 1.2 1.3 Scale

Introduction Indirect determination Direct measurements Combination Conclusions Backup

The lepton differential cross-sections from 8 TeV data

An example compared to simulation

[GeV]µe

TDilepton p

0 50 100 150 200 250

Eve

nts

/ 10

GeV

0

500

1000

1500

2000

2500

3000

3500

4000ATLAS Preliminary

-1 = 8 TeV, 20.2 fbs

Data 2012 Powheg+PY6tt

WtZ+jetsDibosonMis-ID lepton

Powheg+PY6MC@NLO+HWAlpgen+HW

[GeV]µe

TDilepton p

0 50 100 150 200 250

MC

/Dat

a

0.8

1

1.2 Stat. uncert.

− Measure a number of lepton differential distributions in tt→ eµ + X events.

The sensitivity of peµT to mtop

[GeV]µe

TDilepton p

0 50 100 150 200 250 300

ref

σ)/

ref

σ-σ

Nor

mal

ised

(

-0.2

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

0.2

=172.5 GeVt

ref. fit Powheg+PY6 m=165 GeV

talt. fit Powheg+PY6 mdata stat. error

ATLAS Simulation Preliminary

− Correct to stable particle level (using Powheg+Pythia6+CT10), subtract the back-ground and convert into normalised lepton differential cross-sections 1

σxdσxdx .

− Clear sensitivity to mtop for x = p`T, peµT ,meµ, pe

T+pµT , Ee+Eµ, but not for |η`|, |yeµ|,∆Φeµ.

The lepton differential cross-sections can be used to determine mtop or mpoletop .

Measurements of the top quark mass with ATLAS Richard Nisius (MPP Munchen) Venice, July 7, 2017 3 /24

Page 4: Measurements of the top quark mass with the ATLAS detectornisius/talks/VENE070717/Talk.pdfMeasurements of the top quark mass with the ATLAS detector t pp b ... 1 1.1 1.2 1.3 Scale

Introduction Indirect determination Direct measurements Combination Conclusions Backup

The mpoletop mass from lepton differential cross-sections

Comparison to a fixed order prediction

[GeV]µe

TDilepton p

0 50 100 150 200 250 300

pred

ictio

n / d

ata

0.7

0.8

0.9

1

1.1

1.2

1.3

ScalePDFAlphaS

Data uncertainty

MCFM+HERAPDF 1.5

ATLAS Preliminary-1 = 8 TeV, 20.2 fbs

bars = full data uncertainty

−Within the sizeable uncertainties, the fixed order prediction describes the data.

The fitted mpoletop values

TLepton p µe

TDilepton p

µeDilepton m µ

T+pe

TDilepton p

µ+EeDilepton E Comb. (8 dist)

[GeV

] t p

ole

m

160

165

170

175

180

185

CT14MMHTNNPDF 3.0HERAPDF 2.0ABM 11NNPDF nojet

ATLAS Preliminary-1 = 8 TeV, 20.2 fbs

total uncertainty statistical uncertaintyworld-average direct reconstruction

/2 t

=mµMCFM NLO fixed-order,

χ2Ndf =

64−7168

6

��@@

− The results in mpoletop are from fits to individual distributions, or to all distributions (including

|η`|, |yeµ|,∆Φeµ) while constraining the syst. uncertainties with nuisance parameters.− The spread in the individual results is about 6 GeV. The combined result is:

mpoletop = 173.2± 0.9 (stat.)± 0.8 (syst.)± 1.2 (theo.) GeV = 173.2± 1.6 GeV. The theo. un-

certainty is from PDF (0.3 GeV) and fixed vs. dynamic (e.g. ET2 ) scale variations (1.1. GeV).

The first measurement of mpoletop using this method results in an uncertainty of 1.6 GeV.

Measurements of the top quark mass with ATLAS Richard Nisius (MPP Munchen) Venice, July 7, 2017 4 /24

Page 5: Measurements of the top quark mass with the ATLAS detectornisius/talks/VENE070717/Talk.pdfMeasurements of the top quark mass with the ATLAS detector t pp b ... 1 1.1 1.2 1.3 Scale

Introduction Indirect determination Direct measurements Combination Conclusions Backup

The uncertainty in the jet energy scale (JES)

g

g

b - Jet

W

Neutrino

Lepton

b - Jet

Wq - Jet

q - Jet

t

t

t

tt → (b e ν) (b q q), M(qq) = mW, M(bqq) = mtop

νe

b-jet

e

jet

jet

b-jet

− Precise calibrations of the energy scale of inclusive jets(JES) and the relative b-to-light-jet energy scale (bJES)are vital for precise measurements of mtop.

ref

T/pjet

Tp

0 0.5 1 1.5 2 2.5

Eve

nts

0

20

40

60

80

100

120

140

< 80 GeVref

T60 < p

ATLAS Preliminary-1

Ldt=20.3 fb∫=8 TeV, s

R = 0.4, LCW+JEStanti-k

)-jet - Dataµµ ee/→(Z

Jet Z → e+e−µ+µ−

pT,Jet = pT,Z

Calibration via pT - balance

ATL

AS

-CO

NF-

2015

-057

[GeV]jetT

p20 30 40 210 210×2 310 310×2

Frac

tiona

l JES

unc

erta

inty

0

0.02

0.04

0.06

0.08

0.1

ATLAS Preliminary correctionin situ = 0.4, LCW+JES + R tanti-k

= 8 TeVsData 2012, = 0.0η

Total uncertainty JESin situAbsolute JESin situRelative

Flav. composition, inclusive jetsFlav. response, inclusive jetsPileup, average 2012 conditionsPunch-through, average 2012 conditions

ATLAS-CONF-2015-037

JES uncertainty versus Jet - pT

-

0.01 · mtop ≈ 1.7 GeV!− For high precision in mtop the possibility of in-situ cali-

brations of the mean JES and bJES are extremely helpful.

A small JES-induced uncertainty in mtop is indispensible.

Measurements of the top quark mass with ATLAS Richard Nisius (MPP Munchen) Venice, July 7, 2017 5 /24

Page 6: Measurements of the top quark mass with the ATLAS detectornisius/talks/VENE070717/Talk.pdfMeasurements of the top quark mass with the ATLAS detector t pp b ... 1 1.1 1.2 1.3 Scale

Introduction Indirect determination Direct measurements Combination Conclusions Backup

Measurement in the all-jets channel from 8 TeV datap p

tb

b-jet

W+

q

q

jet

jet

t

b

b-jet

W−

qq

jetjet

Ent

ries

/ 2 G

eV

500

1000

1500

2000

2500

3000ATLAS

-1 Ldt = 20.2 fb∫

= 8 TeVsData

MC (Correct)tt

MC (Incorrect)tt

MC (Non-Matched)tt

QCD Multi-jet (Data-Driven)

Syst. Uncertainty⊕Stat.

[GeV]jjm60 70 80 90 100 110

Dat

a / P

redi

ctio

n

0.5

1

1.5

The mjj distribution

Ent

ries

/ 0.0

4

200

400

600

800

1000ATLAS

-1 Ldt = 20.2 fb∫

= 8 TeVsData

MC (Correct)tt

MC (Incorrect)tt

MC (Non-Matched)tt

QCD Multi-jet (Data-Driven)

Syst. Uncertainty⊕Stat.

jj/mjjj = m3/2R1.6 1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4

Dat

a / P

redi

ctio

n

0.5

1

1.5

The R32 distribution Some analysis details

− The number of b-tagged jets amongstthe six leading jets and 〈∆Φ(b,W )〉 inthe signal and three control regionsare used to determine the shape of thebackground distributions from data.

�����− Chosing the R32 =

mjjjmjj

=mbqqmqq

distri-bution (with an ATLAS Exp. expected’peak’ at 172.84

80.37 = 2.15) stabilises mtop

against a global JES uncertainty.

jj/mjjj = m3/2R

1.6 1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4

Ent

ries

/ 0.0

4

0

200

400

600

800

1000

= 8 TeVsData Signal FitBackground FitTotal Fit

ATLAS-1 Ldt = 20.2 fb∫ -1 Ldt = 20.2 fb∫ -1 Ldt = 20.2 fb∫

/ndf = 72.3/48 = 1.512χ

The result from the fit to data

− mtop = 173.72 ± 0.55 (stat) ± 1.01 (syst) GeV− Most important systematic uncertainties: JES (0.60 GeV)

bJES (0.34 GeV) and hadronisation (0.64 GeV).− The summary so far:

Channel (√

s) Stat Model Background ExperimentalAll-jets (8) 0.55 0.70± 0.16 0.19 0.71± 0.04

An about 40% improvement compared to the 7 TeV analysis.

Measurements of the top quark mass with ATLAS Richard Nisius (MPP Munchen) Venice, July 7, 2017 6 /24

Page 7: Measurements of the top quark mass with the ATLAS detectornisius/talks/VENE070717/Talk.pdfMeasurements of the top quark mass with the ATLAS detector t pp b ... 1 1.1 1.2 1.3 Scale

Introduction Indirect determination Direct measurements Combination Conclusions Backup

Three-dimensional lepton + jets analysis from 7 TeV datap p

tb

b-jet

W+

νℓ

ℓ+

t

b

b-jet

W−

qq

jetjet

[GeV]recotopm

130 140 150 160 170 180 190 200 210 220

Eve

nts

/ 2 G

eV

0

200

400

600

800

1000

1200 1b≥data l+jets, =172.5 GeV

top, mtt

Single topW +jetsZ +jetsWW/WZ/ZZNP/fake lep.Uncertainty

[GeV]recotopm

130 140 150 160 170 180 190 200 210 220

Dat

a/M

C0.60.8

11.21.4

ATLAS-1=7 TeV, 4.6 fbs

The analysis idea− (b)JSF = (b)Jet Scale Factor

to obtain scaled jets

p′t (q) = JSF · pt(q)

p′t (b) = JSF · bJSF · pt(b)

1. mrecotop = f(mtop, JSF, bJSF).

[GeV]recoWm

60 70 80 90 100 110

Eve

nts

/ GeV

0

200

400

600

800

1000

1200 1b≥data l+jets, =172.5 GeV

top, mtt

Single topW +jetsZ +jetsWW/WZ/ZZNP/fake lep.Uncertainty

[GeV]recoWm

60 70 80 90 100 110

Dat

a/M

C

0.60.8

11.21.4

ATLAS-1=7 TeV, 4.6 fbs

− Additional dimensions

2. mrecoW = 2E1E2(1− cosθ12)

∝ JSF2

2. mrecoW = f(JSF).

recobqR

0.5 1 1.5 2 2.5 3

Eve

nts

/ 0.1

0

200

400

600

800

1000

1200

1400

1600

1800

2000

2200 1b≥data l+jets, =172.5 GeV

top, mtt

Single topW +jetsZ +jetsWW/WZ/ZZNP/fake lep.Uncertainty

recobqR

0.5 1 1.5 2 2.5 3

Dat

a/M

C

0.60.8

11.21.4

ATLAS-1=7 TeV, 4.6 fbs 3. Rreco

bq =

∑pt(b)∑pt(q)

∝ bJSF·JSFJSF = bJSF

3. Rrecobq = f(bJSF) with a weak mtop dependence.

− The 2D (mrecotop , mreco

W ) or 3D (+Rrecobq ) template fit redu-

ces the JES and bJES induced uncertainties in mtop.− Since the JSF and bJSF are global, but JES and

bJES are f(pt, η), residual uncertainties remain.

This is the first 3D mtop analysis worldwide.

Measurements of the top quark mass with ATLAS Richard Nisius (MPP Munchen) Venice, July 7, 2017 7 /24

Page 8: Measurements of the top quark mass with the ATLAS detectornisius/talks/VENE070717/Talk.pdfMeasurements of the top quark mass with the ATLAS detector t pp b ... 1 1.1 1.2 1.3 Scale

Introduction Indirect determination Direct measurements Combination Conclusions Backup

The list of systematic uncertaintiesDRAFT

tt ! lepton+jets tt ! dilepton Combinationm`+jets

top [GeV] JSF bJSF mdiltop [GeV] mcomb

top [GeV] ⇢

Results 172.33 1.019 1.003 173.79 172.99Statistics 0.75 0.003 0.008 0.54 0.48 0

– Stat. comp. (mtop) 0.23 n/a n/a 0.54– Stat. comp. (JSF) 0.25 0.003 n/a n/a– Stat. comp. (bJSF) 0.67 0.000 0.008 n/a

Method 0.11 ± 0.10 0.001 0.001 0.09 ± 0.07 0.07 0Signal MC 0.22 ± 0.21 0.004 0.002 0.26 ± 0.16 0.24 +1.00Hadronisation 0.18 ± 0.12 0.007 0.013 0.53 ± 0.09 0.34 +1.00ISR/FSR 0.32 ± 0.06 0.017 0.007 0.47 ± 0.05 0.04 �1.00Underlying event 0.15 ± 0.07 0.001 0.003 0.05 ± 0.05 0.06 �1.00Colour reconnection 0.11 ± 0.07 0.001 0.002 0.14 ± 0.05 0.01 �1.00PDF 0.25 ± 0.00 0.001 0.002 0.11 ± 0.00 0.17 +0.57W/Z+jets norm 0.02 ± 0.00 0.000 0.000 0.01 ± 0.00 0.02 +1.00W/Z+jets shape 0.29 ± 0.00 0.000 0.004 0.00 ± 0.00 0.16 0NP/fake-lepton norm. 0.10 ± 0.00 0.000 0.001 0.04 ± 0.00 0.07 +1.00NP/fake-lepton shape 0.05 ± 0.00 0.000 0.001 0.01 ± 0.00 0.03 +0.23Jet energy scale 0.58 ± 0.11 0.018 0.009 0.75 ± 0.08 0.41 �0.23b-Jet energy scale 0.06 ± 0.03 0.000 0.010 0.68 ± 0.02 0.34 +1.00Jet resolution 0.22 ± 0.11 0.007 0.001 0.19 ± 0.04 0.03 �1.00Jet e�ciency 0.12 ± 0.00 0.000 0.002 0.07 ± 0.00 0.10 +1.00Jet vertex fraction 0.01 ± 0.00 0.000 0.000 0.00 ± 0.00 0.00 �1.00b-Tagging 0.50 ± 0.00 0.001 0.007 0.07 ± 0.00 0.25 �0.77Emiss

T 0.15 ± 0.04 0.000 0.001 0.04 ± 0.03 0.08 �0.15Leptons 0.04 ± 0.00 0.001 0.001 0.13 ± 0.00 0.05 �0.34Pile-up 0.02 ± 0.01 0.000 0.000 0.01 ± 0.00 0.01 0Total 1.27 ± 0.33 0.027 0.024 1.41 ± 0.24 0.91 �0.07

Table 3: The measured values of mtop and the contributions of various sources to the uncertainty in the tt !lepton+jets and the tt ! dilepton analyses. The corresponding uncertainties in the measured values of the JSF andbJSF are also shown for the tt ! lepton+jets analysis. The statistical uncertainties associated with these valuesare typically 0.001 or smaller. The result of the mtop combination is shown in the rightmost columns, together withthe correlation (⇢) within each uncertainty group as described in Sect. 8. The symbol n/a stands for not applicable.Values quoted as 0.00 are smaller than 0.005. Finally, the last line refers to the sum in quadrature of the statisticaland systematic uncertainty components.

Pile-upThe residual systematic uncertainty due to pile-up was assessed by determining the dependence of thefitted top quark mass on the amount of pile-up activity, combined with uncertainties in modelling theamount of pile-up in the sample.

7.5. Summary

The resulting sizes of all uncertainties and their sum in quadrature are given in Table 3. The total un-certainties on m`+jets

top , JSF, bJSF and mdiltop, amount to 1.27 GeV, 0.027, 0.024 and 1.41 GeV, respectively.

Within uncertainties, the fitted values of JSF and bJSF are consistent with unity.

16th March 2015 – 15:41 25

Sta

tistic

sM

odel

Bac

kgr.

Exp

erim

enta

l

− The third dimensions reduces the bJES induceduncertainty in mtop from 0.88 to

√0.672 + 0.062

= 0.67, but now it is mostly statistical.− As a side effect a number of MC modelling uncer-

tainties are reduced as well. This is because adifferent bJSF better accounts for the MC diffe-rences than a different mtop.

− The uncertainty in mtop is back to being dominatedby the JES induced uncertainty.

− The summary so far:

Channel (√

s) Stat Model Background ExperimentalAll jets (8) 0.55 0.70± 0.16 0.19 0.71± 0.04

Lepton + jets (7) 0.75 0.53± 0.11 0.31± 0.00 0.82± 0.08

In this channel, the bJES induced uncertainty has finally lost its fright.

Measurements of the top quark mass with ATLAS Richard Nisius (MPP Munchen) Venice, July 7, 2017 8 /24

Page 9: Measurements of the top quark mass with the ATLAS detectornisius/talks/VENE070717/Talk.pdfMeasurements of the top quark mass with the ATLAS detector t pp b ... 1 1.1 1.2 1.3 Scale

Introduction Indirect determination Direct measurements Combination Conclusions Backup

Optimisation in the dilepton channel from 8 TeV datap p

tb

b-jet

W+

νℓ

ℓ+

t

b

b-jet

W−

ℓ−νℓ

[GeV]T,lb

p0 50 100 150 200 250 300 350 400

Eve

nts

/ 10

GeV

1

10

210

310

410

510

610

710Data =172.5 GeV

top, mtt

Uncertainty Single top

NP/fake leptons Z+jetsWW/WZ/ZZ

ATLAS-1=8 TeV, 20.2 fbs

[GeV]T,lb

p0 50 100 150 200 250 300 350 400

Dat

a/M

C

0.81

1.2

The pT ,`b distribution

− The variable pT ,`b denotes the mean pT of the two lepton–b-jet pairs.− The data-to-MC difference in pT ,`b is covered by the hadronisation uncertainty (backup).

requirement [GeV]T,lb

p0 40 70 80 90 100 110 120 130 140 150 160

Tot

al u

ncer

tain

ties

[GeV

]

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

Total Total syst. Stat.

Total theor. Total exp.

ATLAS

Uncertainty vs. pT ,`b

− Using pT ,`b > 120 GeV results in the smallest total uncertainty⇒ final selection.

The optimisation significantly reduces the total uncertainty.

Measurements of the top quark mass with ATLAS Richard Nisius (MPP Munchen) Venice, July 7, 2017 9 /24

Page 10: Measurements of the top quark mass with the ATLAS detectornisius/talks/VENE070717/Talk.pdfMeasurements of the top quark mass with the ATLAS detector t pp b ... 1 1.1 1.2 1.3 Scale

Introduction Indirect determination Direct measurements Combination Conclusions Backup

The result from 8 TeV data

[GeV]recolbm

40 60 80 100 120 140 160

Eve

nts

/ 2 G

eV

0

100

200

300

400

500 Data1% backgroundBest fitUncertainty

ATLAS-1=8 TeV, 20.2 fbs

√s = 7 TeV

√s = 8 TeV Correlations Combinations

m`+jetstop [GeV] mdil

top [GeV] mdiltop [GeV] ρ01 ρ02 ρ12 m7 TeV

top [GeV] mdiltop [GeV] mall

top [GeV]

Results 172.33 173.79 172.99 172.99 173.04 172.84

Statistics 0.75 0.54 0.41 0 0 0 0.48 0.38 0.34Method 0.11 ± 0.10 0.09 ± 0.07 0.05 ± 0.07 0 0 0 0.07 0.05 0.05

Signal Monte Carlo generator 0.22 ± 0.21 0.26 ± 0.16 0.09 ± 0.15 +1.00 +1.00 +1.00 0.24 0.10 0.14Hadronisation 0.18 ± 0.12 0.53 ± 0.09 0.22 ± 0.09 +1.00 +1.00 +1.00 0.34 0.24 0.23Initial- and final-state QCD radiation 0.32 ± 0.06 0.47 ± 0.05 0.23 ± 0.07 −1.00 −1.00 +1.00 0.04 0.24 0.08Underlying event 0.15 ± 0.07 0.05 ± 0.05 0.10 ± 0.14 −1.00 −1.00 +1.00 0.06 0.10 0.02Colour reconnection 0.11 ± 0.07 0.14 ± 0.05 0.03 ± 0.14 −1.00 −1.00 +1.00 0.01 0.03 0.01Parton distribution function 0.25 ± 0.00 0.11 ± 0.00 0.05 ± 0.00 +0.57 −0.29 +0.03 0.17 0.04 0.08

Background normalisation 0.10 ± 0.00 0.04 ± 0.00 0.03 ± 0.00 +1.00 +0.23 +0.23 0.07 0.03 0.04W/Z+jets shape 0.29 ± 0.00 0.00 ± 0.00 0 0 0.16 0.00 0.09Fake leptons shape 0.05 ± 0.00 0.01 ± 0.00 0.08 ± 0.00 +0.23 +0.20 −0.08 0.03 0.07 0.05

Jet energy scale 0.58 ± 0.11 0.75 ± 0.08 0.54 ± 0.04 −0.23 +0.06 +0.35 0.41 0.52 0.41Relative b-to-light-jet energy scale 0.06 ± 0.03 0.68 ± 0.02 0.30 ± 0.01 +1.00 +1.00 +1.00 0.34 0.32 0.25Jet energy resolution 0.22 ± 0.11 0.19 ± 0.04 0.09 ± 0.05 −1.00 0 0 0.03 0.08 0.08Jet reconstruction efficiency 0.12 ± 0.00 0.07 ± 0.00 0.01 ± 0.00 +1.00 +1.00 +1.00 0.10 0.01 0.04Jet vertex fraction 0.01 ± 0.00 0.00 ± 0.00 0.02 ± 0.00 −1.00 +1.00 −1.00 0.00 0.02 0.02b-tagging 0.50 ± 0.00 0.07 ± 0.00 0.03 ± 0.02 −0.77 0 0 0.25 0.03 0.15Leptons 0.04 ± 0.00 0.13 ± 0.00 0.14 ± 0.01 −0.34 −0.52 +0.96 0.05 0.14 0.09Emiss

T 0.15 ± 0.04 0.04 ± 0.03 0.01 ± 0.01 −0.15 +0.25 −0.24 0.08 0.01 0.05Pile-up 0.02 ± 0.01 0.01 ± 0.00 0.05 ± 0.01 0 0 0 0.01 0.05 0.03

Total systematic uncertainty 1.03 ± 0.31 1.31 ± 0.23 0.74 ± 0.29 0.77 0.74 0.61

Total 1.27 ± 0.33 1.41 ± 0.24 0.84 ± 0.29 −0.07 0.00 0.51 0.91 0.84 0.70

− Largest experimental uncertaintiesstem from the jet energy scales.

− Largest modelling uncertainties aredue to Hadronisation and ISR/FSR.

− The summary: Channel (√

s) Value Stat Model Background Experimental TotalAll-jets (8) 173.72 0.55 0.70± 0.16 0.19 0.71± 0.04 1.15 (0.66 %)

Lepton + jets (7) 172.33 0.75 0.53± 0.11 0.31± 0.00 0.82± 0.08 1.27 (0.74 %)Dilepton (8) 172.99 0.41 0.35± 0.09 0.08± 0.01 0.64± 0.04 0.85 (0.49 %)

− The correlations of the estimatorsfor all sources of systematic uncer-tainty are evaluated rather thanassigned (as is commonly done).

����

���������

Look at these lines on next slide

This is the most precise ATLAS measurement and the most precise result in this channel.

Measurements of the top quark mass with ATLAS Richard Nisius (MPP Munchen) Venice, July 7, 2017 10 /24

Page 11: Measurements of the top quark mass with the ATLAS detectornisius/talks/VENE070717/Talk.pdfMeasurements of the top quark mass with the ATLAS detector t pp b ... 1 1.1 1.2 1.3 Scale

Introduction Indirect determination Direct measurements Combination Conclusions Backup

The correlations of the estimators for individual sources

(7 TeV) [GeV]diltopm∆

-0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8

(8

TeV

) [G

eV]

dil

top

m∆

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1+ = ρ 1− = ρ

ATLAS

Dilepton 7 vs. dilepton 8 TeV

(7 TeV) [GeV]l+jetstopm∆

-0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8

(8

TeV

) [G

eV]

dil

top

m∆

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1+ = ρ 1− = ρ

ATLAS

Lepton + jets, 7 vs. dilepton 8 TeV

− ∆m = shift in mass from pairs of samples using 500 pseudo-experiments of the data size.− Each point corresponds to a single (sub-) component, with ρ = +1 or ρ = −1.

h h

bJES: 0.30 ± 0.01 (dil, 8), 0.68 ± 0.02 (dil, 7, ρ = +1), 0.06 ± 0.03 (`+jets, 7, ρ = +1).

i i

ISR/FSR: 0.23 ± 0.07 (dil, 8), 0.47 ± 0.05 (dil, 7, ρ = +1), 0.32 ± 0.06 (`+jets, 7, ρ = −1).

By construction, the correlations to the three-dimensional lepton + jets analysis are small.

Measurements of the top quark mass with ATLAS Richard Nisius (MPP Munchen) Venice, July 7, 2017 11 /24

Page 12: Measurements of the top quark mass with the ATLAS detectornisius/talks/VENE070717/Talk.pdfMeasurements of the top quark mass with the ATLAS detector t pp b ... 1 1.1 1.2 1.3 Scale

Introduction Indirect determination Direct measurements Combination Conclusions Backup

The ATLAS measurements of mtop and mpoletop

[GeV]topm165 170 175 180 185

1

17

0.70± 172.84 Phys. Lett. B761 (2016) 350 ATLAS Comb. June 2016

-1 =4.6 fbintL

JHEP 10 (2015) 121+1-jet) t(tσ 2.1 2.3 ±173.7

-1 =4.6-20.3 fbintL

Eur. Phys. J. C74 (2014) 3109) dilepton t(tσ 2.6 2.5 ±172.9

-1 = 20.2 fbintLarXiv:1702.07546all jets 1.0 )± ( 0.6 1.2 ±173.7

-1 = 20.2 fbintL

Phys. Lett. B761 (2016) 350 dilepton → 0.7 )± ( 0.4 0.8 ±173.0

-1 = 4.7 fbintL

Eur. Phys. J. C75 (2015) 330 dilepton → 1.3 )± ( 0.5 1.4 ±173.8

-1 = 4.7 fbintL

Eur. Phys. J. C75 (2015) 330 l+jets → 1.0 )± 0.7 ± 0.2 ± ( 0.2 1.3 ±172.3

-1 =20.3 fbintLCONF-2014-055single top* 2.0 )± ( 0.7 2.1 ±172.2

-1 = 4.6 fbintL

Eur. Phys. J. C75 (2015) 158all jets 1.2 )± ( 1.4 1.8 ±175.1

-1 - 20.3 fb-1 = 4.6 fbint

summary - May 2017, Ltopm

syst.)± bJSF ± JSF ± tot. (stat. ± top m

σ 1 ±ATLAS Comb. stat. uncertainty

bJSF uncertainty⊕ JSF ⊕stat. total uncertainty

Input to comb.→Preliminary, *

ATLAS Preliminary

? = new since EPS2015

??

? Normalised differential lepton distributions 173.2± 1.6

− The combination of three ATLAS measurements results in:mtop = 172.84 ± 0.34 (stat) ± 0.61 (syst) GeV = 172.84 ± 0.70 GeV (0.40%).

The direct measurements are superior in determining mtop.

Measurements of the top quark mass with ATLAS Richard Nisius (MPP Munchen) Venice, July 7, 2017 12 /24

Page 13: Measurements of the top quark mass with the ATLAS detectornisius/talks/VENE070717/Talk.pdfMeasurements of the top quark mass with the ATLAS detector t pp b ... 1 1.1 1.2 1.3 Scale

Introduction Indirect determination Direct measurements Combination Conclusions Backup

Conclusions

− ATLAS has performed various mpoletop measurements based on novel methods,

e.g. by using tt + 1-jet events and differential distributions of leptonic variables .

− Compared to direct measurements of mtop, these mpoletop determinations are performed

in a well-defined renormalisation scheme, but suffer from larger uncertainties.

− The top quark mtop mass was directly measured in all tt decay channels.

− The dilepton result: mtop = 172.99 ± 0.41 (stat) ± 0.74 (syst) GeV = 172.99 ± 0.84 GeV,

is the most precise ATLAS measurement and the most precise in this channel to date.

− The largest experimental uncertainties stem from the calibration of the jet energy scales.

− The largest modelling uncertainties are due to Hadronisation and ISR/FSR radiation.

− For the combination of this result with other measurements the correlations of the estima-

tors for all sources of systematic uncertainty are evaluated rather than assigned.

− The result is: mtop = 172.84 ± 0.34 (stat) ± 0.61 (syst) GeV = 172.84 ± 0.70 GeV.

Measurements of the top quark mass with ATLAS Richard Nisius (MPP Munchen) Venice, July 7, 2017 13 /24

Page 14: Measurements of the top quark mass with the ATLAS detectornisius/talks/VENE070717/Talk.pdfMeasurements of the top quark mass with the ATLAS detector t pp b ... 1 1.1 1.2 1.3 Scale

Introduction Indirect determination Direct measurements Combination Conclusions Backup

Backup - Transparencies

Measurements of the top quark mass with ATLAS Richard Nisius (MPP Munchen) Venice, July 7, 2017 14 /24

Page 15: Measurements of the top quark mass with the ATLAS detectornisius/talks/VENE070717/Talk.pdfMeasurements of the top quark mass with the ATLAS detector t pp b ... 1 1.1 1.2 1.3 Scale

Introduction Indirect determination Direct measurements Combination Conclusions Backup

Production and decay of top-quark pairs

Production processes

fq/p

fq/p

σqq→tt

Quark-induced,O(10%)

fg/p

fg/p

σgg→tt

Gluon-induced,O(90%)

− For mtop = 172.5 GeV and√

s = 8 TeV, the cross-section is σ(tt) = 253+13

−15 pb, resulting in 250k events per 1/fb.

Decay channels (Vtb ≈ 1)

Decay channels

p ptb

W+

t

bW−

p ptb

b-jet

W+

q

q

jet

jet

t

b

b-jet

W−

qq

jetjet

All-jets channel

All-jets: highest rateO(46%), but largest background.

p ptb

b-jet

W+

νℓ

ℓ+

t

b

b-jet

W−

qq

jetjet

Lepton + jets channel

Lepton + jets: medium rateO(30%), lepton ’tag’, good compromise.

p ptb

b-jet

W+

νℓ

ℓ+

t

b

b-jet

W−

ℓ−νℓ

Dilepton channel

Dilepton: lowest rateO(4%), high purity, incomplete kinematics.

τ+τ 1%

τ+µ 2%

τ+e 2%

µ+µ 1%

µ+e 2%

e+e 1%

e+jets 15%

µ+jets 15%

τ+jets 15%

"jets" 46%

"lepton+jets""dilepton"

The LHC is a top quark factory. In all channels, the systematic uncertainties matter most.

Measurements of the top quark mass with ATLAS Richard Nisius (MPP Munchen) Venice, July 7, 2017 15 /24

Page 16: Measurements of the top quark mass with the ATLAS detectornisius/talks/VENE070717/Talk.pdfMeasurements of the top quark mass with the ATLAS detector t pp b ... 1 1.1 1.2 1.3 Scale

Introduction Indirect determination Direct measurements Combination Conclusions Backup

mpoletop from the normalised differential tt + 1-jet cross-section

even

ts /

0.1

0

100

200

300

400

500

600

700

800ATLAS

-1= 7 TeV, 4.6 fbs

Data

=172.5 GeVt

, mtt

Background

Uncertainty

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

data

/ pr

ed.

0

1

2

The data distribution

− Measure distribution of tt + 1-jet events in the lepton + jets channel in 7 TeV data.

ρs = 340 GeVmtt+1-jet

) sρ,po

le

tm(

R

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

Data

=pole

t+1-jet at NLO+PS for mtt

170 GeV175 GeV180 GeV173.7 GeV (best fit)

ATLAS-1=7 TeV, 4.6 fbs

(parton level)s

ρ0 0.2 0.4 0.6 0.8 1

be

st fi

tR

/ R 0.7

1

1.3

The unfolded distribution

R(mpoletop , ρs) = 1

σtt+1-jet

dσtt+1-jetdρs

(mpoletop , ρs) -

− Unfold to parton level and compareR to the NLO+PS prediction as a function of mpoletop .

Larg

ests

ensi

tivity

iscl

ose

toth

resh

old

− Perform χ2 minimisation to get mpoletop that best describes the data.

− Result: mpoletop = 173.7± 1.5 (stat.)± 1.4 (syst.)+ 1.0

− 0.5 (theo.) GeV = 173.7+ 2.3− 2.1 GeV

The first measurement of mpoletop using this mehod, still with about 2.2 GeV uncertainty.

Measurements of the top quark mass with ATLAS Richard Nisius (MPP Munchen) Venice, July 7, 2017 16 /24

Page 17: Measurements of the top quark mass with the ATLAS detectornisius/talks/VENE070717/Talk.pdfMeasurements of the top quark mass with the ATLAS detector t pp b ... 1 1.1 1.2 1.3 Scale

Introduction Indirect determination Direct measurements Combination Conclusions Backup

mpoletop mass from lepton differential cross-sections - additional info

0 200 400

[p

b]

T/d

d⋅ σ

1/

6−10

5−10

4−10

3−10

2−10

1−10­1

= 8 TeV; L = 20.3 fbs; t t→pp

ATLAS Data l+jets

uncorrelatedδ

totalδ

t = mR,F

µ

/2t = mR,F

µ

/4T = HR,F

µ

/2T = ER,F

µ

[GeV] t

T p

0 200 400

Theory

/Data

0.9

1

1.1

ATLAS Preliminary

The top quark pT spectrum

/2 t

=mµComb. (8 dist), /4T

=HµComb. (8 dist), /2T

_=EµComb. (8 dist),

[GeV

] t p

ole

m

166

168

170

172

174

176

178

CT14MMHTNNPDF 3.0HERAPDF 2.0ABM 11NNPDF nojet

ATLAS Preliminary-1 = 8 TeV, 20.2 fbs

total uncertainty statistical uncertaintyworld-average direct reconstruction

MCFM NLO fixed-order

mpoletop for different scale choices

[GeV]poletm

170 175 180

)t(tσD0 inclusive 3.3 GeV±172.8

)t(tσATLAS inclusive 2.6 GeV±172.9

)t(tσCMS inclusive 1.8 GeV±173.8

tt, mt

TD0 differential p 2.5 GeV±169.1

+1j)t(tσATLAS differential 2.2 GeV±173.7

ATLAS leptonic (8 dist.) 1.6 GeV±173.2

poletm

Stat. Uncertainty

Full Uncertainty

ATLASPreliminary

Comparison of measurements of mpoletop

The largest theoretical uncertainty stems from the choice of the QCD scale.

Measurements of the top quark mass with ATLAS Richard Nisius (MPP Munchen) Venice, July 7, 2017 17 /24

Page 18: Measurements of the top quark mass with the ATLAS detectornisius/talks/VENE070717/Talk.pdfMeasurements of the top quark mass with the ATLAS detector t pp b ... 1 1.1 1.2 1.3 Scale

Introduction Indirect determination Direct measurements Combination Conclusions Backup

Measurement in the all-jets channel from 8 TeV data

p ptb

b-jet

W+

q

q

jet

jet

t

b

b-jet

W−

qq

jetjet

Numbers of events retained in the selection

Event yields (thousands)Cut Data tt all-hadronic (MC)

Initial 850450 2338 ± 1NPV>4 tracks

& no isolated e/µ 33476 308.7 ± 0.6Trigger: 5 jets with pT > 55 GeV & ≥ 6 good jets 16110 241.4 ± 0.5No 2 good jets (ji, jk) within ∆R(ji, jk) < 0.6 7646 142.9 ± 0.4≥ 5 good jets with pT > 60 GeV 3303 51.4 ± 0.2Emiss

T < 60 GeV 3021 46.3 ± 0.2∆φ(bi, bj) > 1.5 1737 30.9 ± 0.2χ2 < 11 645.8 22.3 ± 0.1Nbtag ≥ 2 21.9 6.61 ± 0.08〈∆φ(b,W )〉 < 2 12.9 4.40 ± 0.07

The list of uncertainties

Source of uncertainty ∆mtop [GeV ]

Monte Carlo generator 0.18 ± 0.21Hadronisation modelling 0.64 ± 0.15Parton distribution functions 0.04 ± 0.00Initial/final-state radiation 0.10 ± 0.28Underlying event 0.13 ± 0.16Colour reconnection 0.12 ± 0.16Bias in template method 0.06Signal and bkgd parameterisation 0.09Non all-hadronic tt contribution 0.06ABCD method vs. ABCDEF method 0.16Trigger efficiency 0.08 ± 0.01Lepton/Emiss

T calibration 0.02 ± 0.01Overall flavour-tagging 0.10 ± 0.00Jet energy scale (JES) 0.60 ± 0.05b-jet energy scale (bJES) 0.34 ± 0.02Jet energy resolution 0.10 ± 0.04Jet vertex fraction 0.03 ± 0.01

Total systematic uncertainty 1.01Total statistical uncertainty 0.55

Total uncertainty 1.15

− Results: 7 TeV: mtop = 175.1 ± 1.4 (stat) ± 1.2 (syst) GeV = 175.1 ± 1.8 GeV.8 TeV: mtop = 173.72 ± 0.55 (stat) ± 1.01 (syst) GeV = 173.72 ± 1.16 GeV.

An about 40% improvement compared to the 7 TeV analysis.

Measurements of the top quark mass with ATLAS Richard Nisius (MPP Munchen) Venice, July 7, 2017 18 /24

Page 19: Measurements of the top quark mass with the ATLAS detectornisius/talks/VENE070717/Talk.pdfMeasurements of the top quark mass with the ATLAS detector t pp b ... 1 1.1 1.2 1.3 Scale

Introduction Indirect determination Direct measurements Combination Conclusions Backup

The dilepton channel from 8 TeV data

p ptb

b-jet

W+

νℓ

ℓ+

t

b

b-jet

W−

ℓ−νℓ

Pre-selection of events in 8 TeV data

− Use W+W− → `+`−νν with ` = e, µ.− Quality requirements⇒ 20.2± 0.4 fb−1.− Trigger, good primary vertex≥ 5 tracks.− Electrons: ET > 25 GeV, |η| < 2.47.− Muons: pt > 25 GeV, |η| < 2.5.− ee, µµ channel: Emiss

T > 60 GeVm`` > 15 GeV, |m`` − MZ0 | > 10 GeV.

− eµ channel: HT > 130 GeV.− At least two jets with pt > 25 GeV

and |ηjet| < 2.5.− At least one b-tagged jet (εb = 70%).

− Single top quark production is treated as signal rendering an mtop independent background.

The pre-selection yields about 36k events with 1% background.

Measurements of the top quark mass with ATLAS Richard Nisius (MPP Munchen) Venice, July 7, 2017 19 /24

Page 20: Measurements of the top quark mass with the ATLAS detectornisius/talks/VENE070717/Talk.pdfMeasurements of the top quark mass with the ATLAS detector t pp b ... 1 1.1 1.2 1.3 Scale

Introduction Indirect determination Direct measurements Combination Conclusions Backup

The hadronisation uncertainty in 8 TeV data

p ptb

b-jet

W+

νℓ

ℓ+

t

b

b-jet

W−

ℓ−νℓ

[GeV]T,lb

p100 150 200 250 300 350 400

Eve

nts

/ 10

GeV

1

10

210

310

410

510

610Data =172.5 GeV

top, mtt

Uncertainty Powheg+Herwig

Single top NP/fake leptonsZ+jets WW/WZ/ZZ

ATLAS-1=8 TeV, 20.2 fbs

[GeV]T,lb

p100 150 200 250 300 350 400

Dat

a/M

C

0.81

1.2

− The difference between POWHEG+PYTHIA and POWHEG+HERWIG resultsin an hadronisation induced uncertainty in mtop of 0.22± 0.09 GeV.

For this distribution, the data description is better for the POWHEG+HERWIG event sample.

Measurements of the top quark mass with ATLAS Richard Nisius (MPP Munchen) Venice, July 7, 2017 20 /24

Page 21: Measurements of the top quark mass with the ATLAS detectornisius/talks/VENE070717/Talk.pdfMeasurements of the top quark mass with the ATLAS detector t pp b ... 1 1.1 1.2 1.3 Scale

Introduction Indirect determination Direct measurements Combination Conclusions Backup

Combination - dilepton and lepton + jets at 7 TeV

totalρ

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

tota

l unc

erta

inty

[GeV

]to

pm

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

) = 1.41 GeVdil

top(mσ

) = 1.27 GeVl+jets

top(mσ

) = 0.91 GeVcomb

top(mσ

totalρ) vs. comb

top(mσ

ATLAS-1=7 TeV, 4.6 fbs

The uncertainty in mtop

ρest=-0.07

ρass=+0.51

totalρ

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 [G

eV]

top

m

170.5

171

171.5

172

172.5

173

173.5

174

174.5

175

= 173.79 GeVdiltopm

= 172.33 GeVl+jetstopm

= 172.99 GeVcombtopm

totalρ vs. comb

topm

ATLAS-1=7 TeV, 4.6 fbs

The combined value of mtop

(1) mtop = 172.91 ± 0.50 (stat) ± 1.05 (syst) GeV (assigned ρass,i from world combination).(2) mtop = 172.99 ± 0.48 (stat) ± 0.78 (syst) GeV, (estimated ρest,i ).⇒ σ2

σ1= 0.91

1.16 = 0.78, i.e. a very significant improvement due to the estimated correlations.

The use of the three-dimensional versus the one-dimensional fit is paying off.

Measurements of the top quark mass with ATLAS Richard Nisius (MPP Munchen) Venice, July 7, 2017 21 /24

Page 22: Measurements of the top quark mass with the ATLAS detectornisius/talks/VENE070717/Talk.pdfMeasurements of the top quark mass with the ATLAS detector t pp b ... 1 1.1 1.2 1.3 Scale

Introduction Indirect determination Direct measurements Combination Conclusions Backup

Combination - dilepton at 8 TeV with lepton + jets at 7 TeV

totalρ

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

tota

l unc

erta

inty

[GeV

]to

pm

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

) (7 TeV) = 1.27 GeVl+jets

top(mσ

) (8 TeV) = 0.84 GeVdil

top(mσ

) = 0.70 GeVpair

top(mσ

totalρ) vs.

pair

top(mσ

ATLAS

The uncertainty in mtop

totalρ

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 [G

eV]

top

m170

170.5

171

171.5

172

172.5

173

173.5

174

174.5

175

(7 TeV) = 172.33 GeVl+jetstopm

(8 TeV) = 172.99 GeVdiltopm

= 172.79 GeVpairtopm

totalρ vs. pair

topm

ATLAS

The combined value of mtop

− Large improvement with respect to the more precise result, because the correlationis low, ρ = 0.00� 0.84

1.27 = 0.66⇔ the point of no improvement.

The use of the three-dimensional versus the one-dimensional fit is paying off.

Measurements of the top quark mass with ATLAS Richard Nisius (MPP Munchen) Venice, July 7, 2017 22 /24

Page 23: Measurements of the top quark mass with the ATLAS detectornisius/talks/VENE070717/Talk.pdfMeasurements of the top quark mass with the ATLAS detector t pp b ... 1 1.1 1.2 1.3 Scale

Introduction Indirect determination Direct measurements Combination Conclusions Backup

The various combinations

√s = 7 TeV

√s = 8 TeV Correlations Combinations

m`+jetstop [GeV] mdil

top [GeV] mdiltop [GeV] ρ01 ρ02 ρ12 m7 TeV

top [GeV] mdiltop [GeV] mall

top [GeV]

Results 172.33 173.79 172.99 172.99 173.04 172.84

Statistics 0.75 0.54 0.41 0 0 0 0.48 0.38 0.34Method 0.11 ± 0.10 0.09 ± 0.07 0.05 ± 0.07 0 0 0 0.07 0.05 0.05

Signal Monte Carlo generator 0.22 ± 0.21 0.26 ± 0.16 0.09 ± 0.15 +1.00 +1.00 +1.00 0.24 0.10 0.14Hadronisation 0.18 ± 0.12 0.53 ± 0.09 0.22 ± 0.09 +1.00 +1.00 +1.00 0.34 0.24 0.23Initial- and final-state QCD radiation 0.32 ± 0.06 0.47 ± 0.05 0.23 ± 0.07 −1.00 −1.00 +1.00 0.04 0.24 0.08Underlying event 0.15 ± 0.07 0.05 ± 0.05 0.10 ± 0.14 −1.00 −1.00 +1.00 0.06 0.10 0.02Colour reconnection 0.11 ± 0.07 0.14 ± 0.05 0.03 ± 0.14 −1.00 −1.00 +1.00 0.01 0.03 0.01Parton distribution function 0.25 ± 0.00 0.11 ± 0.00 0.05 ± 0.00 +0.57 −0.29 +0.03 0.17 0.04 0.08

Background normalisation 0.10 ± 0.00 0.04 ± 0.00 0.03 ± 0.00 +1.00 +0.23 +0.23 0.07 0.03 0.04W/Z+jets shape 0.29 ± 0.00 0.00 ± 0.00 0 0 0.16 0.00 0.09Fake leptons shape 0.05 ± 0.00 0.01 ± 0.00 0.08 ± 0.00 +0.23 +0.20 −0.08 0.03 0.07 0.05

Jet energy scale 0.58 ± 0.11 0.75 ± 0.08 0.54 ± 0.04 −0.23 +0.06 +0.35 0.41 0.52 0.41Relative b-to-light-jet energy scale 0.06 ± 0.03 0.68 ± 0.02 0.30 ± 0.01 +1.00 +1.00 +1.00 0.34 0.32 0.25Jet energy resolution 0.22 ± 0.11 0.19 ± 0.04 0.09 ± 0.05 −1.00 0 0 0.03 0.08 0.08Jet reconstruction efficiency 0.12 ± 0.00 0.07 ± 0.00 0.01 ± 0.00 +1.00 +1.00 +1.00 0.10 0.01 0.04Jet vertex fraction 0.01 ± 0.00 0.00 ± 0.00 0.02 ± 0.00 −1.00 +1.00 −1.00 0.00 0.02 0.02b-tagging 0.50 ± 0.00 0.07 ± 0.00 0.03 ± 0.02 −0.77 0 0 0.25 0.03 0.15Leptons 0.04 ± 0.00 0.13 ± 0.00 0.14 ± 0.01 −0.34 −0.52 +0.96 0.05 0.14 0.09Emiss

T 0.15 ± 0.04 0.04 ± 0.03 0.01 ± 0.01 −0.15 +0.25 −0.24 0.08 0.01 0.05Pile-up 0.02 ± 0.01 0.01 ± 0.00 0.05 ± 0.01 0 0 0 0.01 0.05 0.03

Total systematic uncertainty 1.03 ± 0.31 1.31 ± 0.23 0.74 ± 0.29 0.77 0.74 0.61

Total 1.27 ± 0.33 1.41 ± 0.24 0.84 ± 0.29 −0.07 0.00 0.51 0.91 0.84 0.70

− The combined result: mtop = 172.84 ± 0.34 (stat) ± 0.61 (syst) GeV = 172.84 ± 0.70 GeV.

This combination of only three results has a precision of 0.4%.

Measurements of the top quark mass with ATLAS Richard Nisius (MPP Munchen) Venice, July 7, 2017 23 /24

Page 24: Measurements of the top quark mass with the ATLAS detectornisius/talks/VENE070717/Talk.pdfMeasurements of the top quark mass with the ATLAS detector t pp b ... 1 1.1 1.2 1.3 Scale

Introduction Indirect determination Direct measurements Combination Conclusions Backup

Precision measurements and the Standard Model

[GeV]topm165 170 175 180 185

1

17

0.70± 172.84 Phys. Lett. B761 (2016) 350 ATLAS Comb. June 2016

-1 =4.6 fbintL

JHEP 10 (2015) 121+1-jet) t(tσ 2.1 2.3 ±173.7

-1 =4.6-20.3 fbintL

Eur. Phys. J. C74 (2014) 3109) dilepton t(tσ 2.6 2.5 ±172.9

-1 = 20.2 fbintLarXiv:1702.07546all jets 1.0 )± ( 0.6 1.2 ±173.7

-1 = 20.2 fbintL

Phys. Lett. B761 (2016) 350 dilepton → 0.7 )± ( 0.4 0.8 ±173.0

-1 = 4.7 fbintL

Eur. Phys. J. C75 (2015) 330 dilepton → 1.3 )± ( 0.5 1.4 ±173.8

-1 = 4.7 fbintL

Eur. Phys. J. C75 (2015) 330 l+jets → 1.0 )± 0.7 ± 0.2 ± ( 0.2 1.3 ±172.3

-1 =20.3 fbintLCONF-2014-055single top* 2.0 )± ( 0.7 2.1 ±172.2

-1 = 4.6 fbintL

Eur. Phys. J. C75 (2015) 158all jets 1.2 )± ( 1.4 1.8 ±175.1

-1 - 20.3 fb-1 = 4.6 fbint

summary - May 2017, Ltopm

syst.)± bJSF ± JSF ± tot. (stat. ± top m

σ 1 ±ATLAS Comb. stat. uncertainty

bJSF uncertainty⊕ JSF ⊕stat. total uncertainty

Input to comb.→Preliminary, *

ATLAS Preliminary

The mtop combination

− The combination of three ATLAS measurements results in:mtop = 172.84 ± 0.34 (stat) ± 0.61 (syst) GeV = 172.84 ± 0.70 GeV (0.4%).

[GeV] tm165 170 175 180 185

[GeV

]W

m

80.25

80.3

80.35

80.4

80.45

80.5 ATLAS 0.019 GeV± = 80.370 Wm

0.70 GeV± = 172.84 tm

0.24 GeV± = 125.09 Hm

t and mW68/95% CL of m

68/95% CL of Electroweak

t and mW Fit w/o m (Eur. Phys. J. C 74 (2014) 3046)

Consistency of the Standard Model

− The good description of the precise measurements of mW with σ(mW) = 0.02%, mtop withσ(mtop) = 0.4% and MH with σ(MH) = 0.2% (from LHC) is another success of the SM.

The Standard Model has successfully passed another precisions test.

Measurements of the top quark mass with ATLAS Richard Nisius (MPP Munchen) Venice, July 7, 2017 24 /24