Top Physics at the LHC – towards precision physics

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Top Physics at the LHC – towards precision physics

Tancredi Carli (CERN)

Due to time constrains, will not talk about searches with top quarks (very active research area in all experiments) Cover newest measurements only

Many more results available

https://twiki.cern.ch/twiki/bin/view/AtlasPublic/TopPublicResults https://twiki.cern.ch/twiki/bin/view/CMSPublic/PhysicsResultsTOP

After ~20 year top physics has entered precision era

Outline

1) Top anti-top pair production cross section (inclusive and differential)

2) Fiducial measurements on top event final state to constrain top modelling systematics

3) Top Mass measurements

4) Single top production via electroweak interactions

5) Constraints on CKM matrix element V_tb

6) Top production in association with vector bosons

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Inclusive top anti-top pair production via strong interaction

Example diagrams:

Long standing theoretical effort on fixed order QCD calculations 1989 NLO

1998 NLO+NLL 2008 NLO+NNLL 2013 NNLO+NNLL

Cross-Section rises by about 10%

from NLO to NNLO+NNLL QCD

Precision improves from ~12% to ~3% (scale) ~ 8% to 5% (PDF) Uncertainty on parton density function dominate Electroweak corrections also sizeable α_s²~α_ew

NNLO QCD calculation mandatory for precision analysis

Figures and numbers from:

Czakon, Mitov arXiv:1303.6254

Czakon, Mangano, Mitov, Rojo

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Top anti-top production cross section at 7 and 8 TeV

ATLAS arXiv:1406.5375

b-jet acceptance and efficiency ε_b fitted with cross-section ε_eµefficiency to pass lepton selection

kinematic correlation C_b of two b-jets taken from MC

Uncertainties: 7 TeV 8 TeV Statistics 1.7% 0.7%

Analysis systematics 2.3% 2.3%

Luminosity 2.0% 3.1%

Select only electron and muon Lepton-ID and isolation efficiency using Z->ll

Cross section measured counting b-jets

7 TeV 8 TeV Precision achieved: 3.5% 4.0%

For data/theory also consider LHC beam energy uncertainty 0.6% → effect on ttbar cross section ~1.8%

Total inclusive top anti-top cross section Dilepton channel

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Summary of top anti-top production cross section measurements

Excellent agreement of NNLO+NNLL predictions and precise experimental measurements 8 TeV: both measurements are in good agreement with NNLO+NNLL prediction

7 TeV: about 2 sigma tension between ATLAS and CMS measurements

Impressive experimental precision at Tevatron and LHC matching NNLO+NNLO precision of ~5%

LHC has already achieved better precision than latest Tevatron measurements

Most precise results:

CMS JHEP 02 (2014) 024 JHEP 11 (2012) 067

Tevatron combination PRD 89 (2014) 072001

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Differential top anti-top kinematic distributions at Tevatron and LHC

(l+jets channel) D0 CMS Total # events 2500 76000

Signal fraction 75% 80% High statistics for precision measurements larger reach to high pt and high mass

CMS: shift between data and MC prediction ? transverse top momentum

transverse top momentum Tevatron LHC

Transverse top momentum distribution as seen by the detector:

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Differential top anti-top cross sections at Tevatron and LHC

First measurement by CDF 2009 PRL 102 (2009) 222003

Recently: DO FERMILAB-PUB-14-012-E

7 TeV CMS EPJ C 73 (2013) 2339 ATLAS EPJ C 73 (2013) 2206 arXiv:1407.0371

8 TeV CMS CMS-PAS-TOP-12-027

D0 CMS

Data described within Shape shifted with respect to data ?

uncertainties MC: ME(2->2)@NLO+PS or ME(2->n)@LO+PS

Tevatron

Available measurements: Top transverse momentum and top anti-top system kinematics (M_tt, y_tt, p_T,tt) Examples:

Uncertainty Tevatron

absolute LHC shape

Statistics 6-12% 2%

Signal model 4-14% 4%

Detector 3-13% 2%

Background 3-9% 2%

Luminosity 6% -

LHC

shape only

transverse top momentum transverse top momentum

absolute x-section

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Differential top anti-top cross section theory comparisons

Possible explanations - gluon density at large-x ? - electro-weak corrections ? - higher order effects ?

- hadronisation ? ATLAS: NLO QCD gives good agreement at low top pt

Both ATLAS and CMS data lower than NLO QCD predictions at high p_T NLO+NNLL in better agreement

Powheg (ME(2-->2)@NLO+PS) with Pythia χ²/NDF=19/6

with Herwig χ²/NDF=4.8/6 (ok)

Transverse top momentum NLO QCD

Transverse top momentum Transverse top momentum

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Constraints on additional parton radiation systematics

Theory systematics varying

- Renormalisation and factorisation scale changed by factor of 2 in Madgraph (ME(2->n)@LO + PS) - ME-PS matching threshold in Madgraph varied from from default 20 GeV by factor of two

Select 2 b-tagged jets Count additional jets with P_Tjet>30 GeV |eta|<2.4 Gap fraction is probability to emit no additional jet

First ATLAS measurement EPJ C72 (2012) 2043 used to adjust additional parton radiation parameters in MC New measurement: CMS arXiv:1404.3171

ME(2->n)@LO + PS

more radiation Dilepton decay channel

ATLAS and CMS use these results to constrain radiation systematics, e.g. on top mass

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Jet multiplicity in top anti-top events

Variation renormalisation and factorisation scale and matching parameters in MadGraph (ME(2->n)@LO+PS ) Variation of α_s scale and hadronisation tune in Alpgen (ME(2->n)@LO+PS )

used as systematic for additional parton radiation modelling describes data

PTjet>35 GeV

|eta|<2.4

CMS arXiv:1404.3171 ATLAS arXiv:1407.0891

Additional jets Additional jets

Lepton+jet channel Fiducial and fully corrected cross-sections

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Top mass measurement methods

Non-standard techniques 1) NLO QCD comparison to

inclusive and tt+jet cross sections (no MC used) →mass defined in NLO QCD calculation

2) kinematic endpoints (no MC used) 3) B-hadron lifetime

4) J/ψ final states (independent of JSF)

Reconstruct top decay products with kinematic fit based on likelihood (ATLAS) or chi2 (CMS)

M_W

M_top Standard technique: Direct mass reconstruction

Exploit known M

W to constrain physics and detector effect Fit M_top with n additional parameters

1D fit M_top

2D fit M_top and jet scale factor (JSF) exploiting M_W constraint

3D fit M

top, JSF and bJSF (ATLAS 2013) b-JSF relative b-to-light JSF using ratio jet from W-boson and b-jet

Template method (e.g. ATLAS, CDF) fit template of reconstructed top mass from MC to data

Ideogram method (e.g. CMS)

Likelihood function to test compatibility of event kinematics with top decay hypothesis (all good permutations are used)

Matrix element method (e.g. D0)

to calculate signal and background probability density for all parton-jet assignments

as function of M_top and JSF Example l+jet channel:

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Top mass world average 2014

ATLAS-CONF-2014-008

Tevatron combination November 2012 May 2013

LHC combination July 2012 September 2013

World combination March 2014 arXiv:1403.4427

Highest precision in l+jet channel Dilepton channel good precision Fully hadronic channel respectable

Combination using BLUE

precision on M_top 0.44%

Consistency χ²=4/10

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Stability of top mass world combination with varying assumptions

Correlation of systematics often not well known →test stability

Good progress on systematic uncertainty harmonisation in TopLHCWG

Detailed correlation studies on detector uncertainty and

final state modelling in top events at LHC

Largest effect on M_top:

- Jet measurement - MC modelling

- Treatment of hadronisation systematics Variation of M_top with varying assumptions:

assumed correlation between

ATLAS/CMS (LHC), CDF/D0 (TEV) and LHC and Tevatron experiments (COL)

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New CMS top mass measurements at 8TeV

Top mass after kinematic fit Kinematic fit to reconstruct top decay product, Ideogram method (all permutations used) Fit M

top and jet scale factor exploiting M

W in l+jets and fully hadronic channel classification using parton match in MC

Top mass after kinematic fit

fully hadronic TOP-14-002

July 2014 l+jets TOP-14-001

March 2014

precision: 0.45% precision: 0.53%

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New D0 top mass measurement

^D0 arXiv:1405.1756 accepted by PRL

Select 4 jets, 1 b-tag 2500 events Blinded analysis

Leading order matrix element to

calculate signal and background probability density 2d fit M_top and jet scale factor (JSF)

exploiting M

W constraint

Precision 0.43%

Mass of W-boson and top anti-top system after top mass fit

Recent improvements:

- faster matrix element calculation by O(100) - large MC statistics →reduced fluctuations on systematic uncertainties to <10 MeV

- updated jet energy measurement uncertainties - dedicated correction for b-jets

- constrain QCD radiation using Drell-Yan events

W-boson mass Top anti-top system mass

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Recent top mass measurements summary

Uncertainty on top mass measurements well below 1 GeV !

Ongoing discussion how to interpret the MC-based results in terms of M_top parameter in SM Lagrangian Effect expected to be O(1) GeV

→ Important to measure M_topwith alternative techniques, e.g. from cross-section

Recent review on mass interpretation Moch et al. arXiv:1405.4781, Juste et al. arXiv:1310.0799

Status July 2014

Measurements included in world average (March 2014) consistent Tension between recent D0 and CMS measurements

To know significance need careful evaluation of systematic uncertainty correlation

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Top mass determination from inclusive top anti-top cross section

CMS Phys. Lett. B 728 (2013) 496 ATLAS arXiv:1406.5375

Comparing NNLO+NNLL QCD top pair cross section to data determine top mass in a well defined renormalisation scheme (here: pole mass) and theory uncertainties

M_top dependence of measured cross section -0.28%/GeV

NNLO+NNLL cross-section Prediction for various PDFs (band scale uncertainty)

Largest exp. syst. (luminosity) uncorrelated for 7 and 8 TeV Results consistent within 1.7 sigma

Combined result:

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Top mass determination from inclusive top anti-top cross section

Recently also first determination of top mass from single top cross section arXiv:1406.4403

However, low sensitivity

Recently new techniques proposed e.g. based on ttbar+jet cross section Alioli et al. EPJ C73 (2013) 2438

Precision 1.5%

NLO+NNLL

NNLO+NNLL

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Electroweak single top production - t-channel

O(α_s) diagram enhanced by large g(x,Q2)

Select lepton, cut on Etmiss/M

Select two or three jets with 1 or 2 b-tagTW

Enhance signal combining many kinematic variable to NN discriminant

In high purity region NN>0.8

Neural net discriminant

reconstructed top mass

precision 13% Good agreement with NLO QCD

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Differential single Top cross section

Transverse top momentum

First differential cross section measurement for single top production

Good description of data by NLO QCD⁽χ²=7.55/5)

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Single top production – t-channel at 8 TeV

Single top and single anti-top cross section

Select lepton, cut on E_Tmiss/M_TW,select two jets with one b-tag W+jet and ttbar background shape determined in control regions (2.jet 0-tag and 3-jet, 2-tag) and fitted

Fit forward jet pseudo-rapidity distribution

Precision 8.6% and 14.2%

Total single top cross section well described by NLO QCD 2014: NNLO available, NNLO/NLO correction small

Bruchseifer, Caola, Melnikov arXiv:1404.7116

CMS arXiv:1403.7366

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t-channel single top production at 8 TeV

First fiducial cross section measurement for single top production defined using particles within detector and analysis acceptance

Single extraction via likelihood to a NN discriminant based on kinematic variables Extrapolation for fiducial to total cross section based on various of MC

ATLAS-CONF-2014-007

Total cross section obtained from fiducial measurement

14% cross section precision NLO QCD based MC give best description of fiducial cross section

→ extrapolate to total cross section:

aMC@NLO ME(2->n)@NLO + PS NLO+NNLL theory uncertainty smaller than extrapolation differences from various MC

ME(2->n)@NLO + PSME(2->3)@LO + PS

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Electroweak single top production summary

Search phase is over

Many results exists already:

-determination of CKM matrix element Vtb -constrains on anomalous couplings

-flavour changing neutral currents etc -polarisation and CP-violation

-investigations on b-quark and gluon PDF

t-channel established at Tevatron At LHC high statistics and S/B~2 -First differential measurements -First fiducial measurements

-Measurement of top anti-top and ratio

process seen ? Tevatron LHC

t-ch. yes 16% 10%

Wt-ch. yes 22%

s-ch. yes 19% <2.1 σ

_SM

Single top cross section precision:

All single top processes established !

2009 (s+t) 2014

CMS PRL. 112 (2014) 23180

ATLAS ATLAS-CONF-2013-100

ATLAS arXiv:1406.7844 2014

D0 and CDF combination on discriminant level

significance: 6.3 sigma

t-channel Wt-channel

s-channel Evidence

D0 PLB 726 (2013) 656 PRL 112 (2014) 231805

CDF PRL 112 (2014) 231804

Observation

D0 and CDF PRL 112 (2014) 231803

CMS

Significance: 0.7 sigma upper cross section limit 2.1xSM cross section i.e. 11.5 pb at 95% CL

Evidence from LHC 7 TeV data 3.4 sigma ATLAS, PLB 716 (2012) 142

4.0 sigma CMS, PRL 110 (2013) 022003

Observation at LHC 8 TeV

CMS PRL. 112 (2014) 23180

ATLAS ATLAS-CONF-2013-100

CMS 6.1 sigma ATLAS 4.2 sigma

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CMSarXiv:1404.2292

CDFPRD 87 (2013) 111101 PRL 112 (2014) 221801

Tevatron measurement on low side

Recent CDF measurement differs from SM by 1.8 sigma Recent CMS measurement close to 1

Top branching ratio to Wb

Result Tevatron LHC

σ

_{single top} ^7-10% ^5-10%

R

^4-8% ^1-2%

CKM matrix element V

tb precision R obtained from counting b-jets

Tests of structure of Wtb-vertex

Conversion to V_tb

R: unitarity of CKM matrix Single top cross section:

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Top anti-top production in association with W/Z bosons

ttZ ttW

Experimental signature number of leptons Garzelli et al JHEP 1211(2012) 056 Campbell/Eliis JHEP 1207 (2012) 052

Process allow test of electroweak coupling of the top quar^k

W Z tt ttV

2 0 2

1 1 2

2 2

2 1 3

1 2 3

2 2 4

2 lepton

4 lepton 3 lepton NLO QCD cross section about 200 fb

CMS:

2l same-sign all flavours, 3l, 4l (counting) ATLAS:

2l opposite (using NN based on kinematics) 2l same sign (muon only), 3l (counting)

Campbell/Eliis

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Top anti-top production in association with W/Z bosons

Evidence for top anti-top production in association with W or Z boson on 3 sigma level

CMS 7 TeV PRL 110 (2013) 172002

CMS 8 TeV arXiv:1406.7830

reconstructed Z boson mass reconstructed top mass Example 3 leptons

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Top anti-top production in association with W/Z bosons

Example:

3 lepton in Z mass region 4 jets, 1 b-tag

2 leptons same+opposite sign and 3 leptons combined:

ATLAS ATLAS-CONF-2014-038

SM σ /σ ratio assumed No assumption on σ /σ

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Conclusion

About 20 years after its discovery top quark physics has reached excellent precision

● Top pair production cross section: 3-4% LHC (single measurement), 5.5% Tevatron (combination)

● All single top production modes observed, t-channel cross section precision about 10%

● Top mass reached ~0.5% precision

World average excellent agreement between measurements Tension between measurement published after world average Can we use these M_top measurements in electro-weak fits ?

● Pole mass from cross section 1.5% precision

● Evidence for W/Z-bosons produced in association with top pair: ttZ, ttW

● Detailed measurements of top quark properties like spin and polarization

● Almost all results limited by systematic uncertainties → crucial to better understand : Modelling of top final state, addition QCD radiation and b-jet fragmentation

Concept of fiducial measurement (quote measurement within detector acceptance)

allows for separation modelling and experimental uncertainty → first differential precision measurement

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Back-up

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Charge asymmetry

ATLAS-CONF-2014-012 ATLAS JHEP02(2014)107 CMS JHEP 04 (2014) 191

Combination CMS PAS TOP-14-006 D0 arXiv:1403.1294

Asymmetry (A) appears at NLO QCD as interference effect of terms to O(α_s³)

Only in qqbar final state

Forward-backward A_FB in ppbar Top/anti-top A_C in pp Large experimental and theory activity due to

CDF and D0 papers in 2008 Forward-backward central-non-central

arXiv:1406.1798

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Differential asymmetry measurements

ATLAS JHEP02(2014)107 CMS JHEP 04 (2014) 191

Combination CMS PAS TOP-14-006 D0 arXiv:1403.1294

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Simultaneous measurement WW and top anti-top pair cross section

Dilepton cross section measured as function of Etmiss and N_jet

Simultaneous measurement of

WW, ttbar and Z-->tau tau cross section

WW and ttbar cross section both low for NLO (large scale uncertainties)

NNLO needed

Fiducial cross section measured:

Reduction in extrapolation uncertainties from detector acceptance to inclusive phase space X%

Main reduction due to PDF uncertainties XXX Top pair cross section

WW pair cross sectionZZ pair cross section

N_jet Etmiss

ttbar high high

WW medium medium

ZZ-->

ττ

^low ^low

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Top mass determination from inclusive top anti-top cross section

CMS Phys. Lett. B 728 (2013) 496

By comparing NNLO QCD top pair cross section to data a top mass is determined in a well defined renormalisation scheme (here: pole mass) and theory uncertainties CMS dilepton ttbar cross section at 7 TeV used JHEP 11 (2012) 067

at M_top=172.5 GeV Mass dependence of cross section is evaluated

NNLO+NNLL prediction for various PDFs

Mtop=176.7^+3.8_-3.4 GeV

Recently also first determination of top mass From single top cross section arXiv:1406.4403

However, low sensitivity

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CMS dilepton result on Inclusive top pair production

CMS JHEP 02 (2014) 024

Partial 8 TeV data-set

Two leptons p_T>20 GeV |η|<2.1

Two jets with p_T>30 GeV |η|<2.5 (1 b-tagged) All channels ee, eµ, µµ

Systematic uncertainty:

3% ttbar modelling PDF not quoted

3% lepton energy and identification 2.6% luminosity

Precision achieved: 5.4%, Exp analysis systematics: 5.3%

Luminosity 2.6%

beam: not quoted

Cross-section from counting events

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Summary of top pair production cross section measurements

7 TeV 8 TeV

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Summary of single top production cross section measurements

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Differential top anti-top cross section theory comparisons

Possible explanations - gluon density at large-x ? - electro-weak corrections ? - higher order effects ?

- hadronisation ?

(Powheg+Herwig describes data) Prediction describe Tevatron data within uncertainties by NLO QCD

Both ATLAS and CMS see data lower than predictions at high p_T

Transverse top momentum Transverse top momentum

Tevatron LHC

NLO QCD

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Differential top anti-top cross section theory comparisons at LHC

Invariant mass of top anti-top system

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Ttbar event topology for Pythia Herwig parton showers

When switching from Pythia to Herwig in Powheg, changes in the ttbar event kinematics are observed

In p_Ttop Powheg+Herwig is in

better agreement with data (not shown) Powheg+Herwig describes additional radiation

Confirmed by ATLAS simulation (not shown)

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Constraints on additional radiation systematics in ATLAS

Take pragmatic approach: tune MCs to measured observables sensitive to radiations Jet gap fraction measurement ATLAS EPJ C72 (2012) 2043

Dilepton channel with two b-tags Fraction of events that do not have additional central jet above a pt-cut

Settings estimated before measurement

See more details in talk by Liza Mijovic

After tuning

Reduction of systematics by tuning ISR/FSR parameter in ACERMC (see back-up for details) Central CMS MC Madgraph+Pythia+Z2 tune describes data well

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Measurement of jet transverse momenta in top pair events

Lepton+jets channel decay channel

Powheg+Pythia (ME(2->2)@NLO+PS) is ATLAS default → to hard high-pt jets Can be adjusted by changing hdamp parameter controlling ME/PS matching

Powheg+Pythia and MC@NLO+Herwig both ME(2->2)@NLO+PS give different predictions

→ can constrain “choices” on ME/PS matching and hadronisation

Additional jet Jet from top decay

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Jet multiplicity in top anti-top events

PTjet>30 GeV

|eta|<2.4

Variation renormalisation and factorisation scale and matching parameters in MadGraph (ME(2->n)@LO + PS ) used as systematic for additional parton radiation modelling gives good description of data

PTjet>35 GeV

|eta|<2.4

CMS arXiv:1404.3171

Dilepton decay channel Lepton+jets channel decay channel

Additional jets Additional jets

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Top production in association with W/Z bosons

Example

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Differential ttbar kinematic distribution at Tevatron and LHC

Top transverse momentum and top anti-top system kinematics (M_tt, y_tt, p_T,tt)

Tevatron LHC

DO CMS Total # events 2500 76000 Signal fraction ~75% 80%

(l+jets channel)

High statistics for precision measurements Reach to high pt and high mass

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Differential ttbar cross sections at Tevatron and LHC

Top transverse momentum and top anti-top system kinematics (M_tt, y_tt, p_T,tt)

First measurement by CDF 2009 PRL 102 (2009) 222003 Recently: DO FERMILAB-PUB-14-012-E

7 TeV CMS EPJ C 73 (2013) 2339 , ATLAS EPJ C 73 (2013) 2206, ATLAS-CONF-2013-099

8 TeV CMS CMS-PAS-TOP-12-027

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Differential ttbar cross section

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Short history of top theory and modelling

Top final state modelling in

Monte Carlo simulation generators

~1980 Hadronisation and additional parton

~1990 ME(2->2)@LO + PS Pythia/Herwig

~ 2001 ME(2->n)@LO + PS Multi-jet merging of ME and PS Alpgen, Sherpa, Madgraph... cross section Born accuracy 2->n

parton shower in leading-logarithm accuracy

~ 2002 ME(2->2)@NLO+PS NLO matching

MC@NLO, Powheg cross section NLO accuracy hardest emission from ME

parton shower in leading-logarithm accuracy

2010-14 ME(2->n)@NLO + PS NLO matched multi-jet merging Sherpa, aMC@NLO

Many precision measurement limited by systematic uncertainties on MC modelling of top final state Monte Carlo modelling of high jet multiplicities important for searches, ttH, VLQ, SUSY etc.

actively used experiments

under

development

from F Krauss

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Single top production via electroweak interaction

In LO classified according to W-boson exchange

Examples: Single top t-channel

2004-09 NLO

2011-13 NLO+NNLL

2014 NNLO (only 1/N_c²neglected) 2009

NLO implementation with merged parton shower in

MC@NLO/Powheg 2014

Madgraph5_aMC@NLO automated NLO calculations matched with PS in 4 and 5 flavour scheme

NF=5 with massless quark flavours

N_F=4 light flavour+ heavy flavour with m_b

2→3 with b-quark PDF generated perturbatively

→ important for description of second b-quark t-channel

2→2 N

F=5

t-channel 2→3 N_F=5

Wt-channel

Enhanced by g(x,Q2)

s-channel

Bruchseifer, Caola, Melnikov arXiv:1404.7116

t-channel single top cross section calculations at 8 TeV

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Single Top – Wt-channel at 8 TeV

Evidence for Wt-production from LHC 7 TeV data 3.4 sigma ATLAS, PLB 716 (2012) 142

4.0 sigma CMS, PRL 110 (2013) 022003

CMS 6.1 sigma

CMS:

Select two leptons and 1-bjet and large Etmiss Separate Wt-signal from main ttbar background with BDT classifier based on 13 kinematic variables

Significance CMS 6.1 sigma ATLAS 4.2 sigma

Observation of Wt production

ATLAS-CONF-2013-100

PRL. 112 (2014) 23180

precision ~22%

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s-channel top production at Tevatron and LHC

Evidence

D0 PLB 726 (2013) 656 PRL 112 (2014) 231805 CDF PRL 112 (2014) 231804

Observation

D0 and CDF PRL 112 (2014) 231803

Multi-variate techniques to enhance signal D0 and CDF combination on discriminant level Observed significance: 6.3 sigma

First observation of s-channel process First observation through combination

precision 19%

Recent CMS results based on 8 TeV data

CMS-PAS-TOP-13-009

Analysis based on multi-variate technique BDT Observed significance 0.7 sigma

Upper cross section limit 2.1 SM cross section, i.e. 11.5 pb at 95% CL

3.8 σ

3.7 σ 4.2σ

6.3 σ

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Single Top production summary

Beyond LO channel separation not clear, e.g. ttbar vs Wt Proposal for better definition in terms for fiducial regions

enhancing certain processes (Frederix, TopLHCWG May 2014)

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Systematic uncertainties in new mass measurements

CMS D0

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New CMS top mass measurement

CMS PAS TOP-14-001

Select 4jets, 2 b-tags

Exploit 100k events (94% pure top) 30k well reconstructed events

Measure M_top as function of event topology using simple fit to M_top(1D)

Important cross check

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Top mass world average 2014

ATLAS-CONF-2014-008

Tevatron combination November 2012 May 2013

LHC combination July 2012 September 2013

World combination March 2014 arXiv:1403.4427

Highest precision in l+jet channel Dilepton channel good precision Fully hadronic channel respectable Combination using BLUE

Intrinsic information weight

Precision on M_top using MC 0.44%

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ATLAS top mass measurement

l+jet, channel b-tagging

Reconstructed M_top for various true M_top

Reconstructed M_top for various JSF

Reconstructed M_top for various b-jJSF

Selected uncertainties 3d template techniques

to determine 1) Mtop,

2) jet scale factor (JSF) using M

3) b-jet scale factor (b-JSF)W

using

Large hadronisation and b-jet scale systematics attenuated with 3d-fit

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Top anti-top production in association with W/Z bosons

ttZ

ttW