electroweak and qcd aspects in v+jetsrabbertz/office/... · gustaf hällströmin katu 2 p.o.box 64...

Gustaf Hällströmin katu 2 P.O.Box 64 00014 University of Helsinki FINLAND

T +358-2-941 50564 [email protected] [email protected] voutila.web.cern.ch

UNIVERSITY OF HELSINKI AND

HELSINKI INSTITUTE OF PHYSICS

Dear Dr. Henning Kirschenmann,

I would like to offer you the position of a post-doctoral researcher in our CMS Experiment project at the Helsinki Institute of Physics, starting January 1st, 2017, and extending until the end of the current project on 31st December, 2018. The contract is extendible by 3 years (up to December 2021) by mutual agreement, assuming the approval of the CMS Experiment project into the next 3-year period.

Helsinki Institute of Physics coordinates the Finnish participation in the CERN experiments and is an inde-pendent research institute within University of Helsinki, which is among the top 100 universities world-wide [1]. Finland participates in the CMS experiment and has leading roles in the tracker upgrade, tracker align-ment, jet calibration and CMS OpenData. Our physics analyses cover topics varying from Charged Higgs searches and neutral Higgs searches to top quark mass measurements, b physics and jet physics.

Our CMS Experiment group is composed of two professors (prof. Paula Eerola, director of HIP; asst. prof. Mikko Voutilainen), three senior scientists (Kati Lassila-Perini, Sami Lehti, Tapio Lampen) and six PhD stu-dents (T. Järvinen, J. Pekkanen, J. Heikkilä, S. Laurila, J. Havukainen, H. Siikonen). We also enlist several emerita and adjoint scientists (J. Tuominiemi, T. Linden, L. Wendland, M. Kortelainen).

Your responsibilities would include physics analysis, experimental physics responsibilities and leadership within CMS experiment (we especially encourage shift captain work, JEC EPR and development of your leadership within JetMET), supervision and advising of graduate students (in particular on SUSY Higgs searches and top quark mass), organization of national and international workshops and conferences, and actively applying for available funding (e.g. foundations post-doc pool, Academy of Finland post-docs, uni-versity post-docs, as well as travel funding from various foundations). The position includes some outreach activities and 5% of teaching.

We offer:

• Nationally competitive salary (salary level 5/5, i.e. about 3500 €/month), which includes healthcare, social security and pension

• Up to 4-month transition period at CERN before moving to Finland (remuneration 1500 €/month)

• Travel budget of 5000 €/anno within the project budget constraints

• Removal expenses of up to 2000 €

We would like to hear back from you by November 29th, 2016, in order to be able to arrange the necessary paper work for next year in time for a January 1st—31st , 2017 start, given your positive reply.

Best regards,

Asst. prof. Mikko Voutilainen, Project leader of the CMS Experiment project at HIP University of Helsinki and Helsinki Institute of Physics In Helsinki on November 9th, 2016

[1] #91 (#96, #67) according to QS World University Ranking in 2016 (2015,2014).

Henning Kirschenmann (Helsinki Institute of Physics) on behalf of the CMS Collaboration

Electroweak and QCD aspects in V+Jets

7 July 2018

[pb]

σPr

oduc

tion

Cro

ss S

ectio

n,

5−10

4−10

3−10

2−10

1−10

1

10

210

310

410CMS PreliminaryApril 2018

All results at: http://cern.ch/go/pNj7

W 1j≥ 2j≥ 3j≥ 4j≥ 5j≥ 6j≥ 7j≥ 1c 2b

and kinematic selectionγγ→ll, H→, Zνl→s with WσFiducial W, Z and H Z 1j≥ 2j≥ 3j≥ 4j≥ 5j≥ 6j≥ 7j≥ 1c 1b≥ 2b≥ =0j

WZ =1j =2j 3j≥ =0jZZ =1j =2j 3j≥ tt 1j 2j 3j 4j 2b =0j

H =1j =2j =3j >=4j

)-1 5.0 fb≤7 TeV CMS measurement (L )-1 19.6 fb≤8 TeV CMS measurement (L )-1 35.9 fb≤13 TeV CMS measurement (L

Theory prediction

[pb]

σPr

oduc

tion

Cro

ss S

ectio

n,

4−10

3−10

2−10

1−10

1

10

210

310

410

510

CMS PreliminaryMay 2018

All results at: http://cern.ch/go/pNj7

W

n jet(s)≥

Z

n jet(s)≥

γW γZ WW WZ ZZµll, l=e,→, Zνl→EW: W

qqWEW qqZ

EWWW→γγ

γqqWEW

ssWW EW

γqqZEW

qqZZEW γWV γγZ γγW tt

=n jet(s)

t-cht tW s-cht γtt tZq ttW ttZ ttttσ∆ in exp. Hσ∆Th.

ggH qqHVBF VH WH ZH ttH HH

CMS 95%CL limits at 7, 8 and 13 TeV

)-1 5.0 fb≤7 TeV CMS measurement (L )-1 19.6 fb≤8 TeV CMS measurement (L )-1 35.9 fb≤13 TeV CMS measurement (L

Theory prediction

2

W+JetsPhys. Rev. D 96 (2017) 0720052015 data

Z+JetsarXiv:1804.05252 2015 data

arXiv:1712.098142016 dataAccepted (EPJC): 5 July

+EWK Z + 2 JetsHere: +γ+JetsarXiv:1807.007822015 dataSubmitted: 3 July

V+HF CMS results in following talk

Motivation

3

! Precision measurements of [differential] V+Jets production cross sections stringent tests of SM predictions ! sensitive to higher order (QCD and EWK effects)! sensitive to non perturbative effects (e.g. particle emission, parton

shower)! also targeting explicitly EWK production mode (VBF, soft QCD

modeling)! Comparison of the measurements with predictions motivates additional

Monte Carlo (MC) generator development and improves our understanding of the prediction uncertainties.

! V+jets is dominant background for: ! Top quark measurements ! Higgs physics ! VH (H→bb) ! Searches for new physics

W+JetsPhys. Rev. D 96 (2017) 0720052015 data

Z+JetsarXiv:1804.05252 2015 data

Here: +EWK Z + 2 Jets+γ+JetsarXiv:1807.007822015 dataSubmitted: 3 July

arXiv:1712.098142016 dataAccepted (EPJC): 5 July

Theoretical prediction for cross section for Z+jetsI MADGRAPH5 AMC@NLO + Pythia8 (denoted as LO MG5 aMC)

I LO matrix element up to 4 partonsI kT -MLM merging between matrix element and parton showerI NNPDF3.0 LO PDF, CUETP8M1 Pythia8 tune

4 partons

I MADGRAPH5 AMC@NLO + Pythia8 (denoted as NLO MG5 aMC)I NLO matrix element up to 2 partons (LO accuracy for 3 partons)I FxFx jet merging between matrix element and parton showerI NNPDF3.0 NLO PDF, CUETP8M1 Pythia8 tune

3 partons

4

Theoretical prediction for cross section for Z+jetsI MADGRAPH5 AMC@NLO + Pythia8 (denoted as LO MG5 aMC)

I LO matrix element up to 4 partonsI kT -MLM merging between matrix element and parton showerI NNPDF3.0 LO PDF, CUETP8M1 Pythia8 tune

4 partons

I MADGRAPH5 AMC@NLO + Pythia8 (denoted as NLO MG5 aMC)I NLO matrix element up to 2 partons (LO accuracy for 3 partons)I FxFx jet merging between matrix element and parton showerI NNPDF3.0 NLO PDF, CUETP8M1 Pythia8 tune

3 partons

4

MADGRAPH5_AMC@NLO + Pythia8 ! LO: up to 4 partons; kT-MLM merging ME—>PS! NNPDF3.0 LO PDF, CUETP8M1 Pythia8 tune

! NLO: up to 2 partons; FxFx jet merging ME—> PS ! NNPDF3.0 NLO PDF, CUETP8M1 Pythia8 tune

Theoretical predictions for W/Z+jet cross sections

4

GENEVA 1.0-RC2 (GE) (for Z+jet only)! NNLO matrix elements + NNLL resummation ! PDF4LHC15 NNLO, CUETP8M1 Pythia8 tune

Z/W+1 jet fixed order NNLO! Correction for hadronization and multiple parton interaction computed

with NLO MG5 aMC+Pythia8 as differential scaling factors; CT14 (Z)/ NNPDF 3.0 NNLO (W)

Samples 0j 1j 2j 3j 4j >4j Cross section [pb]

LO MG5_aMC LO LO LO LO LO PS 5787NLO MG5_aMC NLO NLO NLO LO PS PS 5931Geneva NLO NLO LO PS PS PS 5940Z/W+1@NNLO - NNLO NLO LO - - 134.6

Differential Z+jet cross sections

5

! leptons: pT>30 GeV; |η|<2.4! m(ll)=91±20 GeV! pT(jet)>30 GeV; |η|<2.4; ΔR(jet,l)>0.4

! pp collisions 2015: 2.19/fb! Backgrounds estimated from simulation! ttbar dominant background at high jet

multiplicities

! Unfolding to generator level for many observables: NJets; pT(jet1/2/3); y(jet1/2/3); HT; pT balance; jet-Z balance (JZB)

Z+JetsarXiv:1804.05252

19

2−10

1−10

1

10

210

310

410Measurement

2j NLO + PS)≤MG5_aMC + PY8 (

4j LO + PS)≤MG5_aMC + PY8 (

)0+NNLOτ

GE + PY8 (NNLL’

CMS (13 TeV)-12.19 fb

(R = 0.4) jetsTkAnti-| < 2.4 jet > 30 GeV, |yjet

TpZ/γ

∗→ ℓ+ℓ−, N

jets≥ 1

[pb

]je

ts/d

Nσd

Mea

sure

men

tPr

edict

ion

0.60.8

11.21.4

Stat theo⊕ unc. sα ⊕ PDF ⊕

Mea

sure

men

tPr

edict

ion

0.60.8

11.21.4

Stat unc.

jetsN= 0 = 1 = 2 = 3 = 4 = 5 = 6

Mea

sure

men

tPr

edict

ion

0.60.8

11.21.4

Stat theo unc. ⊕

2−10

1−10

1

10

210

310

410Measurement



)0+NNLOτ

GE + PY8 (NNLL’

CMS (13 TeV)-12.19 fb


TpZ/γ

∗→ ℓ+ℓ−, N

jets≥ 1

[pb

]je

ts/d

Nσd

Mea

sure

men

tPr

edict

ion

0.60.8

11.21.4


Mea

sure

men

tPr

edict

ion

0.60.8

11.21.4

Stat unc.

jetsN 0≥ 1≥ 2≥ 3≥ 4≥ 5≥ 6≥

Mea

sure

men

tPr

edict

ion

0.60.8

11.21.4

Stat theo unc. ⊕

Figure 4: Measured cross section for Z + jets as a function of the jet exclusive (left) and inclu-sive (right) multiplicity. The error bars represent the statistical uncertainty and the grey hatchedbands represent the total uncertainty, including the systematic and statistical components. Themeasurement is compared with different predictions, which are described in the text. The ra-tio of each prediction to the measurement is shown together with the measurement statistical(black bars) and total (black hatched bands) uncertainties and the prediction (coloured bands)uncertainties. Different uncertainties were considered for the predictions: statistical (stat), MEcalculation (theo), and PDF together with the strong coupling constant (aS). The complete setwas computed for one of the predictions. These uncertainties were added together in quadra-ture (represented by the � sign in the legend).

20

0.5

1

1.5

2

2.5

3

3.5

4Measurement



)0+NNLOτ

GE + PY8 (NNLL’

CMS (13 TeV)-12.19 fb


TpZ/γ

∗→ ℓ+ℓ−, N

jets≥ 1

(Z)

[pb/

GeV

]T

/dp

σdM

easu

rem

ent

Pred

ictio

n

0.60.8

11.21.4 Stat theo⊕ unc. sα ⊕ PDF ⊕

Mea

sure

men

tPr

edict

ion

0.60.8

11.21.4 Stat unc.

(Z) [GeV]T

p10 210 310

Mea

sure

men

tPr

edict

ion

0.60.8

11.21.4 Stat theo unc. ⊕

Figure 5: Measured cross section for Z + jets as a function of the transverse momentum of theZ boson for events with at least one jet. Other details are as mentioned in the Fig. 4 caption.

included, the peak of pbalT is shifted to larger values. The measurement is in good agreement

with NLO MG5 aMC predictions. The slopes of the distributions for the first two jet multiplic-ities predicted by LO MG5 aMC do not fully describe the data. This observation indicates thatthe NLO correction is important for the description of hadronic activity beyond the jet accep-tance used in this analysis, pT > 30 GeV and |y| > 2.4. An imbalance in the event, i.e. pbal

T notequal to zero, requires two partons in the final state with one of the two out of the acceptance.Such events are described with NLO accuracy for the NLO MG5 aMC sample and LO accu-racy for the two other samples. In the case of the GENEVA simulation, when at least two jets arerequired, as in the second plot of Fig. 12, the additional jet must come from parton showeringand this leads to an underestimation of the cross section, as in the case of the jet multiplicitydistribution. When requiring two jets within the acceptance, the NLO MG5 aMC prediction,which has an effective LO accuracy for this observable, starts to show discrepancies with themeasurement. The estimated theoretical uncertainties cover the observed discrepancies.

The JZB distribution is shown in Figs. 14 and 15 (Tables 18–20) for the inclusive one-jet events,in the full phase space, and separately for pT(Z) below and above 50 GeV. As expected in thehigh-pT(Z) region, i.e. in the high jet multiplicity sample, the distribution is more symmetric.The NLO MG5 aMC prediction provides a good description of the JZB distribution, while bothGENEVA and LO MG5 aMC predictions do not. This applies to both configurations, JZB < 0and > 0. This observation indicates that the NLO correction is important for the descriptionof hadronic activity beyond the jet acceptance used in this analysis.

Differential Z+jet cross sections

6

21

2−10

1−10

1

10

Measurement



)0+NNLOτ

GE + PY8 (NNLL’

NNLO (1j NNLO)jettiN

CMS (13 TeV)-12.19 fb


TpZ/γ

∗→ ℓ+ℓ−, N

jets≥ 1

) [p

b/G

eV]

1(j T/d

pσd

Mea

sure

men

tPr

edict

ion

0.60.8

11.21.4


Mea

sure

men

tPr

edict

ion

0.60.8

11.21.4

Stat unc.

Mea

sure

men

tPr

edict

ion

0.60.8

11.21.4

Stat theo unc. ⊕

) [GeV]1

(jT

p50 100 150 200 250 300 350 400

Mea

sure

men

tPr

edict

ion

0.60.8

11.21.4

Stat theo unc. ⊕

Figure 6: Measured cross section for Z + jets as a function of the transverse momentum of thefirst jet. Other details are as mentioned in the Fig. 4 caption.

! GE: shape at low pT(Z) and pT(jet1) dependence well modelled

! LO MG5_aMC: significant differences! NLO MG5_aMC and Z+1@NNLO: NLO

needed to describe measurement


Differential W+jet cross sections

7

! pT(μ)>30 GeV; |η|<2.4; MT> 50 GeV! pT(jet)>30 GeV; |η|<2.4; ΔR(jet,l)>0.4

! pp collisions 2015: 2.2/fb! Backgrounds estimated from simulation

(QCD multijet data-driven)! ttbar dominant background at high jet

multiplicities

! Unfolding to generator level for many observables: NJets; pT(jet1/2/3/4); y(jet1/2/3/4); HT; ΔΦ(μ,jet1/2/3/4); ΔR(μ,closest jet)

W+JetsPhys. Rev. D 96 (2017) 072005

LO MG_aMC prediction is given only with its statisticaluncertainty. The NLO MG_aMC FxFx prediction is givenwith both the statistical and systematic uncertainties.Systematic uncertainties in the NLO MG_aMC FxFxprediction are obtained by varying the NNPDF 3.0 NLOPDFs and the value of αs, and by varying independently therenormalization and factorization scales by a factor of 0.5and 2. All possible combinations are used in variations ofscales excluding only the cases where one scale is varied bya factor of 0.5 and the other one by a factor of 2. The totalsystematic uncertainty is the squared sum of these uncer-tainties. The systematic uncertainty due to variation of scalefactors for the exclusive jet multiplicity distribution iscomputed using the method described in Refs. [46,47].For the NNLO prediction, the theoretical uncertaintyincludes both statistical and systematic components, wherethe systematic uncertainty is calculated by varying inde-pendently the central renormalization and factorizationscales by a factor of 2 up and down, disallowing thecombinations where one scale is varied by a factor of 0.5and the other one by a factor of 2.0.The measured differential cross sections as functions of

the exclusive and inclusive jet multiplicities up to 6 jets arecompared with the predictions of LO MG_aMC and NLO

MG_aMC FxFx in Fig. 3. The measured cross sections andthe predictions are in good agreement within uncertainties.The measured cross sections for inclusive jet multiplic-

ities of 1–4 are compared with the predictions as a functionof the jet pT (jyj) in Fig. 4 (Fig. 5). The measured crosssections as functions of the jetpT and jyj are better describedby the NLO MG_aMC FxFx prediction for all inclusive jetmultiplicities and by the NNLO calculation for at least onejet. The LO MG_aMC prediction exhibits a slightly lowertrend in estimating data in contrast to NLO MG_aMC FxFxand NNLO on jet pT and jyj distributions, particularly at lowpT and for inclusive jet multiplicities of 1–3.The measured cross sections as functions of the HT

variable of the jets, which is sensitive to the effects ofhigher order corrections, are compared with the predictions.The HT distributions for inclusive jet multiplicities of 1–4are shown in Fig. 6. The predictions are in good agreementwith data for the HT spectra of the jets for all inclusive jetmultiplicities, with the exception of LO MG_aMC, whichslightly underestimates the data at low HT.The differential cross sections are also measured as

functions of angular variables: the azimuthal separationΔϕðμ; jiÞ between the muon and the jet for inclusive jetmultiplicities of 1–4, and the angular distance between the

jetsN= 1 = 2 = 3 = 4 = 5 = 6

1−10

1

10

210

310

410

Data

2j NLO + PS)≤MG_aMC FxFx + PY8 (

4j LO + PS)≤MG_aMC + PY8 (

CMS

(13 TeV)-12.2 fb

(R = 0.4) JetsTanti-k| < 2.4

jet > 30 GeV, |yjet

Tp

) + jetsνµW(

[pb

]je

ts/d

Nσd

jetsN= 1 = 2 = 3 = 4 = 5 = 6

MG

_aM

C F

xFx/

Dat

a

0.5

1

1.5

Syst. + stat. unc. (gen)

jetsN= 1 = 2 = 3 = 4 = 5 = 6

MG

_aM

C/D

ata

0.5

1

1.5

Stat. unc. (gen)

jetsN 1≥ 2≥ 3≥ 4≥ 5≥ 6≥

1−10

1

10

210

310

410

Data



CMS

(13 TeV)-12.2 fb

(R = 0.4) JetsTanti-k| < 2.4

jet > 30 GeV, |yjet

Tp

) + jetsνµW(

[pb

]je

ts/d

Nσd

jetsN 1≥ 2≥ 3≥ 4≥ 5≥ 6≥

MG

_aM

C F

xFx/

Dat

a

0.5

1

1.5


jetsN 1≥ 2≥ 3≥ 4≥ 5≥ 6≥

MG

_aM

C/D

ata

0.5

1

1.5

Stat. unc. (gen)

FIG. 3. Differential cross section measurement for the exclusive (left) and inclusive jet multiplicities (right), compared to thepredictions of NLO MG_aMC FxFx and LO MG_aMC. The black circular markers with the gray hatched band represent the unfoldeddata measurement and the total experimental uncertainty. The LO MG_aMC prediction is given only with its statistical uncertainty. Theband around the NLO MG_aMC FxFx prediction represents its theoretical uncertainty including both statistical and systematiccomponents. The lower panels show the ratios of the prediction to the unfolded data.

MEASUREMENT OF THE DIFFERENTIAL CROSS … PHYSICAL REVIEW D 96, 072005 (2017)

072005-7


8

W+JetsPhys. Rev. D 96 (2017) 072005

) [GeV]1

(jT

p

3−10

2−10

1−10

1

10

Data



NNLOjettiN

CMS

(13 TeV)-12.2 fb

(R = 0.4) JetsTanti-k| < 2.4

jet > 30 GeV, |yjet

Tp

1-jet≥) + νµW(

) [p

b/G

eV]

1(jT

/dp

σd

) [GeV]1

(jT

p

MG

_aM

C F

xFx/

Dat

a

0.5

1

1.5


) [GeV]1

(jT

p

MG

_aM

C/D

ata

0.5

1

1.5

Stat. unc. (gen)

) [GeV]1

(jT

p100 200 300 400 500 600 700 800 900

NN

LO/D

ata

0.5

1

1.5


) [GeV]2

(jT

p

3−10

2−10

1−10

1

10

Data



CMS

(13 TeV)-12.2 fb

(R = 0.4) JetsTanti-k| < 2.4

jet > 30 GeV, |yjet

Tp

2-jets≥) + νµW(

) [p

b/G

eV]

2(jT

/dp

σd) [GeV]

2(j

Tp

MG

_aM

C F

xFx/

Dat

a0.5

1

1.5


) [GeV]2

(jT

p50 100 150 200 250 300 350 400 450 500

MG

_aM

C/D

ata

0.5

1

1.5

Stat. unc. (gen)

) [GeV]3

(jT

p

3−10

2−10

1−10

1

10Data



CMS

(13 TeV)-12.2 fb

(R = 0.4) JetsTanti-k| < 2.4

jet > 30 GeV, |yjet

Tp

3-jets≥) + νµW(

) [p

b/G

eV]

3(jT

/dp

σd

) [GeV]3

(jT

p

MG

_aM

C F

xFx/

Dat

a

0.5

1

1.5


) [GeV]3

(jT

p50 100 150 200 250 300

MG

_aM

C/D

ata

0.5

1

1.5

Stat. unc. (gen)

) [GeV]4

(jT

p

3−10

2−10

1−10

1Data



CMS

(13 TeV)-12.2 fb

(R = 0.4) JetsTanti-k| < 2.4

jet > 30 GeV, |yjet

Tp

4-jets≥) + νµW(

) [p

b/G

eV]

4(jT

/dp

σd

) [GeV]4

(jT

p

MG

_aM

C F

xFx/

Dat

a

0.5

1

1.5


) [GeV]4

(jT

p40 60 80 100 120 140 160 180

MG

_aM

C/D

ata

0.5

1

1.5

Stat. unc. (gen)

FIG. 4. Differential cross section measurement for the transverse momenta of the four leading jets, shown from left to right for at least1 and 2 jets (upper) and for at least 3 and 4 jets (lower) on the figures, compared to the predictions of NLO MG_aMC FxFx and LOMG_aMC. The NNLO prediction for W þ 1-jet is included in the first leading jet pT. The black circular markers with the gray hatchedband represent the unfolded data measurement and the total experimental uncertainty. The LO MG_aMC prediction is given only withits statistical uncertainty. The bands around the NLO MG_aMC FxFx and NNLO predictions represent their theoretical uncertaintiesincluding both statistical and systematic components. The lower panels show the ratios of the prediction to the unfolded data.

A. M. SIRUNYAN et al. PHYSICAL REVIEW D 96, 072005 (2017)

072005-8

! NLO MG5_aMC : Overall best description ! LO MG5_aMC: underestimating at low jet pT! W+1@NNLO: better description of shape for

pT of leading jet than LO

) [GeV]1

(jT

p

3−10

2−10

1−10

1

10

Data



NNLOjettiN

CMS

(13 TeV)-12.2 fb

(R = 0.4) JetsTanti-k| < 2.4

jet > 30 GeV, |yjet

Tp

1-jet≥) + νµW(

) [p

b/G

eV]

1(jT

/dp

σd

) [GeV]1

(jT

p

MG

_aM

C F

xFx/

Dat

a

0.5

1

1.5


) [GeV]1

(jT

p

MG

_aM

C/D

ata

0.5

1

1.5

Stat. unc. (gen)

) [GeV]1

(jT

p100 200 300 400 500 600 700 800 900

NN

LO/D

ata

0.5

1

1.5


) [GeV]2

(jT

p

3−10

2−10

1−10

1

10

Data



CMS

(13 TeV)-12.2 fb

(R = 0.4) JetsTanti-k| < 2.4

jet > 30 GeV, |yjet

Tp

2-jets≥) + νµW(

) [p

b/G

eV]

2(jT

/dp

σd

) [GeV]2

(jT

p

MG

_aM

C F

xFx/

Dat

a

0.5

1

1.5


) [GeV]2

(jT

p50 100 150 200 250 300 350 400 450 500

MG

_aM

C/D

ata

0.5

1

1.5

Stat. unc. (gen)

) [GeV]3

(jT

p

3−10

2−10

1−10

1

10Data



CMS

(13 TeV)-12.2 fb

(R = 0.4) JetsTanti-k| < 2.4

jet > 30 GeV, |yjet

Tp

3-jets≥) + νµW(

) [p

b/G

eV]

3(jT

/dp

σd

) [GeV]3

(jT

p

MG

_aM

C F

xFx/

Dat

a

0.5

1

1.5


) [GeV]3

(jT

p50 100 150 200 250 300

MG

_aM

C/D

ata

0.5

1

1.5

Stat. unc. (gen)

) [GeV]4

(jT

p

3−10

2−10

1−10

1Data



CMS

(13 TeV)-12.2 fb

(R = 0.4) JetsTanti-k| < 2.4

jet > 30 GeV, |yjet

Tp

4-jets≥) + νµW(

) [p

b/G

eV]

4(jT

/dp

σd

) [GeV]4

(jT

p

MG

_aM

C F

xFx/

Dat

a

0.5

1

1.5


) [GeV]4

(jT

p40 60 80 100 120 140 160 180

MG

_aM

C/D

ata

0.5

1

1.5

Stat. unc. (gen)

FIG. 4. Differential cross section measurement for the transverse momenta of the four leading jets, shown from left to right for at least1 and 2 jets (upper) and for at least 3 and 4 jets (lower) on the figures, compared to the predictions of NLO MG_aMC FxFx and LOMG_aMC. The NNLO prediction for W þ 1-jet is included in the first leading jet pT. The black circular markers with the gray hatchedband represent the unfolded data measurement and the total experimental uncertainty. The LO MG_aMC prediction is given only withits statistical uncertainty. The bands around the NLO MG_aMC FxFx and NNLO predictions represent their theoretical uncertaintiesincluding both statistical and systematic components. The lower panels show the ratios of the prediction to the unfolded data.


072005-8


9

W+JetsPhys. Rev. D 96 (2017) 072005

Angular observables! ΔΦ(μ,jet1): sensitive

to the implementation of particle emissions and other (non) perturbative effects modeled by PS algorithms in event generators

! ΔR(μ,closest jet): probes contribution of electroweak radiative processes to W+jets

! Decent modelling of angular observables by all predictions: LO MG5_aMC, NLO MG5_aMC, W+1@NNLO

)1

,jµ(φ∆

210

310

Data



NNLOjettiN

CMS

(13 TeV)-12.2 fb

(R = 0.4) JetsTanti-k| < 2.4

jet > 30 GeV, |yjet

Tp

1-jet≥) + νµW(

) [p

b]1,jµ(φ∆

/dσd

)1

,jµ(φ∆

MG

_aM

C F

xFx/

Dat

a

0.5

1

1.5


)1

,jµ(φ∆

MG

_aM

C/D

ata

0.5

1

1.5

Stat. unc. (gen)

)1

,jµ(φ∆0 0.5 1 1.5 2 2.5 3

NN

LO/D

ata

0.5

1

1.5


)2

,jµ(φ∆

10

210

Data



CMS

(13 TeV)-12.2 fb

(R = 0.4) JetsTanti-k| < 2.4

jet > 30 GeV, |yjet

Tp

2-jets≥) + νµW(

) [p

b]2,jµ(φ∆

/dσd

)2

,jµ(φ∆

MG

_aM

C F

xFx/

Dat

a

0.5

1

1.5


)2

,jµ(φ∆0 0.5 1 1.5 2 2.5 3

MG

_aM

C/D

ata

0.5

1

1.5

Stat. unc. (gen)

)3

,jµ(φ∆

10

210

Data



CMS

(13 TeV)-12.2 fb

(R = 0.4) JetsTanti-k| < 2.4

jet > 30 GeV, |yjet

Tp

3-jets≥) + νµW(

) [p

b]3,jµ(φ∆

/dσd

)3

,jµ(φ∆

MG

_aM

C F

xFx/

Dat

a

0.5

1

1.5


)3

,jµ(φ∆0 0.5 1 1.5 2 2.5 3

MG

_aM

C/D

ata

0.5

1

1.5

Stat. unc. (gen)

)4

,jµ(φ∆

1

10

Data



CMS

(13 TeV)-12.2 fb

(R = 0.4) JetsTanti-k| < 2.4

jet > 30 GeV, |yjet

Tp

4-jets≥) + νµW(

) [p

b]4,jµ(φ∆

/dσd

)4

,jµ(φ∆

MG

_aM

C F

xFx/

Dat

a

0.5

1

1.5


)4

,jµ(φ∆0 0.5 1 1.5 2 2.5 3

MG

_aM

C/D

ata

0.5

1

1.5

Stat. unc. (gen)

FIG. 7. Differential cross section measurement for Δϕðμ; jiÞ, shown from left to right for at least 1 and 2 jets (upper) and for at least 3and 4 jets (lower) on the figures, compared to the predictions of NLO MG_aMC FxFx and LO MG_aMC. The NNLO prediction forW þ 1-jet is included in Δϕðμ; j1Þ for one jet inclusive production. The black circular markers with the gray hatched band represent theunfolded data measurement and the total experimental uncertainty. The LO MG_aMC prediction is given only with its statisticaluncertainty. The bands around the NLO MG_aMC FxFx and NNLO predictions represent their theoretical uncertainties including bothstatistical and systematic components. The lower panels show the ratio of the prediction to the unfolded data.

MEASUREMENT OF THE DIFFERENTIAL CROSS … PHYSICAL REVIEW D 96, 072005 (2017)

072005-11

muon and the closest jet ΔRðμ; closest jetÞ in events withone or more jets. The measured Δϕðμ; jiÞ distributions arecompared with the predictions in Fig. 7 and they are welldescribed within uncertainties. This observable is sensitiveto the implementation of particle emissions and othernonperturbative effects modeled by parton showeringalgorithms in MC generators.The comparison of the measured ΔRðμ; closest jetÞ with

the predictions is shown in Fig. 8. This observable probesthe angular correlation between the muon emitted in the Wboson decay and the direction of the closest jet. In thecollinear region (small ΔR values), it is sensitive to themodeling of W boson radiative emission from initial- orfinal-state quarks. The predictions are observed to be infairly good agreement with data within the uncertainties,but there are some differences. Around ΔR ¼ 2.0–2.5, inthe transition between the region dominated by back-to-back W þ N ≥ 1-jet processes (high ΔR) and the region

where the radiative W boson emission should be enhanced(low ΔR), the NLO MG_aMC FxFx prediction over-estimates the measured cross section. In the high-ΔRregion, the LO MG_aMC prediction underestimates thedata, which is consistent with the other observables.

X. SUMMARY

The first measurement of the differential cross sectionsfor a W boson produced in association with jets in proton-proton collisions at a center-of-mass energy of 13 TeV waspresented. The collision data correspond to an integratedluminosity of 2.2 fb−1 and were collected with the CMSdetector during 2015 at the LHC.The differential cross sections are measured using the

muon decay mode of the W boson as functions of theexclusive and inclusive jet multiplicities up to a multiplicityof six, the jet transverse momentum pT and absolute valueof rapidity jyj for the four leading jets, and the scalar pTsum of the jets HT for an inclusive jet multiplicity up tofour. The differential cross sections are also measured as afunction of the azimuthal separation between the muondirection from the W boson decay and the direction of theleading jet for up to four inclusive jets, and of the angulardistance between the muon and the closest jet in events withat least one jet.The background-subtracted data distributions are

corrected for all detector effects by means of regularizedunfolding and compared with the predictions ofMADGRAPH5_aMC@NLO at leading-order (LO) accuracy(LO MG_aMC) and at next-to-LO (NLO) accuracy (NLOMG_aMC FxFx). The measured data are also comparedwith a calculation based on the N-jettiness subtractionscheme at next-to-NLO (NNLO) accuracy for W þ 1-jetproduction.The predictions describe the data well within uncertain-

ties as functions of the exclusive and inclusive jet multi-plicities and are in good agreement with data for the jet pTspectra, with the exception of the LOMG_aMC prediction,which underestimates the data at low to moderate jet pT.The measured HT distributions are well modeled both bythe NLO MG_aMC FxFx prediction for all inclusive jetmultiplicities and the NNLO calculation forW þ 1-jet. TheLO MG_aMC prediction underestimates the measuredcross sections at low HT. All predictions accuratelydescribe the jet jyj distributions and the cross sections asa function of the azimuthal correlation between the muonand the leading jet. The measured cross section as afunction of the angular distance between the muon andthe closest jet, which is sensitive to electroweak emission ofW bosons, is best described by the NNLO calculation.

ACKNOWLEDGMENTS

We extend our thanks to Radja Boughezal forproviding the NNLO predictions for this analysis [9,31].

, closest jet)µR(∆

1−10

1

10

Data



NNLOjettiN

CMS

(13 TeV)-12.2 fb

(R = 0.4) JetsTanti-k| < 2.4

jet > 300 GeV, |y

lead jet

T > 100 GeV, pjet

Tp

1-jet≥) + νµW(

,clo

sest

jet)

[pb

]µ

R(

∆/dσd


MG

_aM

C F

xFx/

Dat

a

0.5

1

1.5



MG

_aM

C/D

ata

0.5

1

1.5

Stat. unc. (gen)

, closest jet)µR(∆0 0.5 1 1.5 2 2.5 3 3.5 4

NN

LO/D

ata

0.5

1

1.5


FIG. 8. Differential cross section measurement forΔRðμ; closest jetÞ for one jet inclusive production, comparedto the predictions of NLO MG_aMC FxFx, LO MG_aMC, andthe NNLO calculation. All jets in the events are required to havepT > 100 GeV, with the leading jet pT > 300 GeV. The blackcircular markers with the gray hatched band represent theunfolded data measurement and the total experimental uncer-tainty. The LO MG_aMC prediction is given only with itsstatistical uncertainty. The bands around the NLO MG_aMCFxFx and NNLO predictions represent their theoretical uncer-tainties including both statistical and systematic components. Thelower panels show the ratio of the prediction to the unfolded data.


072005-12

Angular variables

Sandeep Kaur V+jets at CMS June 5, 2018 13/17

➢ ∆φ(μ, jet): All predictions accurately describe the data

➢ ∆Rmin

(μ, jet): predictions are in fairly good agreement with data within the uncertainties

➢ ∆φ (μ, jet) is sensitive to the implementation of particle emissions and other (non) perturbative effects modeled by PS algorithms in event generators

➢ ∆Rmin

(μ, jet) probes contribution of electroweak radiative processes to W+jets

pT(j) > 100 GeV

pT(j

1) > 100 GeV

Phys.Rev.D 96 (2017) 072005

Small ∆R: collinear W emission

Large ∆R: W balanced by hadronic recoil

Angular variables

Sandeep Kaur V+jets at CMS June 5, 2018 13/17

➢ ∆φ(μ, jet): All predictions accurately describe the data

➢ ∆Rmin

(μ, jet): predictions are in fairly good agreement with data within the uncertainties

➢ ∆φ (μ, jet) is sensitive to the implementation of particle emissions and other (non) perturbative effects modeled by PS algorithms in event generators

➢ ∆Rmin

(μ, jet) probes contribution of electroweak radiative processes to W+jets

pT(j) > 100 GeV

pT(j

1) > 100 GeV

Phys.Rev.D 96 (2017) 072005

Small ∆R: collinear W emission

Large ∆R: W balanced by hadronic recoil

small ΔR: collinear

Large ΔR: W balanced by hadronic recoil

7

BDT output1− 0.5− 0 0.5 1

Entr

ies

0

5

10

15

310×

< 220 GeVTγ| < 1.5, 200 < Ejet| < 1.44, |yγ |y

Data 28156 eventsFitted 28159.5 events

183.6 events±SIG 22638.3 Background

(13 TeV)-12.26 fb

CMSPreliminary

BDT output1− 0.5− 0 0.5 1

Dat

aσ

(Dat

a-Fi

t)/

4−2−024 /dof = 0.28 2χ

BDT output1− 0.5− 0 0.5 1

Entr

ies

2

4

310×

< 220 GeVTγ| < 1.5, 200 < Ejet| < 2.5, |yγ 1.57 < |y

Data 13976 eventsFitted 13976.1 events

145.3 events±SIG 8656.4 Background

(13 TeV)-12.26 fb

CMSPreliminary

BDT output1− 0.5− 0 0.5 1

Dat

aσ

(Dat

a-Fi

t)/

4−2−024 /dof = 0.54 2χ

Figure 2: Distributions of the BDT output for an EB (left) and an EE (right) bin with photonET between 200–220 GeV and |yjet| < 1.5. The points represent data, and the solid histograms,approaching the data points, represent the fit results with the signal (dashed) and background(dotted) components displayed. The bottom panels show the ratio of the difference betweenthe data and the fit to the statistical uncertainty in the data, along with the resulting reducedc2 over degrees of freedom (dof).

applied on the photon yields, due to the selection of the sideband range is also considered as asystematic uncertainty.

The impact on photon yields from the unfolding uncertainties, which include photon energyscale and resolution uncertainties, is roughly 5%. The uncertainties of the event selection effi-ciency due to the jet selection and jet rapidity migration are negligible.

The uncertainty in the measurement of the CMS integrated luminosity is 2.3% [19].

The total uncertainty in the yield per bin, excluding the highest photon ET bin in each y range,is about 5–8% for EB and 9–17% for EE photons. The highest photon ET bins in all y regionhave limited events in data and simulated samples for the evaluation of systematics.

7 Results and comparison with theory

The measured inclusive isolated-photon and photon+jets cross sections are shown in Figs. 3and 5, respectively, and in Tables 2 and 3.

The measured cross sections are compared with NLO perturbative QCD calculations from theJETPHOX 1.3.1 generator [11, 42, 43], using the NNPDF3.0 NLO [13] PDFs and the Bourhis-Fontannaz-Guillet (BFG) set II parton fragmentation functions [44]. The renormalization, fac-torization, and fragmentation scales are all set to be equal to the photon ET. To estimate theeffect of the choice of theoretical scales on the predictions, the three scales are varied indepen-

Differential γ+jet cross sections

10

! Photon yields are extracted using the shape of BDT distributions.

! Template for background taken from control region

! Measured inclusive (+ jets) cross sections double (triple) differential in photon ET , y, (rapidity of the highest pT jet), are compared to NLO QCD calculations (Jetphox 1.3.1)

γ+JetsarXiv:1807.00782

Differential γ+jet cross sections

11

! Cross-sections in agreement with NLO (Jetphox 1.3.1) within uncertainties, in all kinematic regions.


13

(GeV)TE210×2 210×3 210×4 210×5 310

(pb/

GeV

)je

t d

yγ

dy Tγ /

dEσ3 d

-410

-110

210

510

810

1010 )6 10× > 30GeV ( jet

T| < 2.4, pjet| < 2.5, 1.5 < |yγ1.57 < |y

)4 10× > 30GeV ( jetT

| < 1.5, pjet| < 2.5, |yγ1.57 < |y

)2 10× > 30GeV ( jetT

| < 2.4, pjet| < 1.44, 1.5 < |yγ|y

> 30GeV jetT

| < 1.5, pjet| < 1.44, |yγ|y

NLO JETPHOX NNPDF 3.0

(13 TeV)-12.26 fbCMS Preliminary

Figure 5: Differential cross sections for photon+jets production in two photon rapidity bins,|yg| < 1.44 and 1.57 < |yg| < 2.5, and two jet rapidity bins, |yjet| < 1.5 and 1.5 < |yjet| < 2.4.The points show the measured values with their total uncertainties, and the lines show theNLO JETPHOX predictions with the NNPDF3.0 PDF set.

15

(GeV)TE210×2 210×3 210×4 210×5 310

Theo

ry /

Data

0.5

1

1.5

2 (13 TeV)-12.26 fbCMS Preliminary| < 0.8γ|y

Data experimental unc.NLO JETPHOX NNPDF3.0NLO JETPHOX CT14NLO JETPHOX MMHT14NLO JETPHOX HERAPDF2.0NNPDF3.0 total theoretical unc.

(GeV)TE210×2 210×3 210×4 210×5 310

Theo

ry /

Data

0.5

1

1.5

2 (13 TeV)-12.26 fbCMS Preliminary| < 1.44γ0.8 < |y


(GeV)TE210×2 210×3 210×4 210×5 310

Theo

ry /

Data

0.5

1

1.5



(GeV)TE210×2 210×3 210×4 210×5 210×6

Theo

ry /

Data

0.5

1

1.5



(GeV)TE210×2 210×3 210×4 210×5 310

Theo

ry /

Data

0.5

1

1.5

2 (13 TeV)-12.26 fbCMS Preliminary > 30GeVjet

T| < 1.5, pjet| < 1.44, |yγ|y

Data experimental unc.NLO JETPHOX NNPDF3.0NLO JETPHOX CT14NO JETPHOX MMHT14NLO JETPHOX HERAPDF2.0NNPDF3.0 total theoretical unc.

(GeV)TE210×2 210×3 210×4 210×5 310

Theo

ry /

Data

0.5

1

1.5


T| < 2.4, pjet| < 1.44, 1.5 < |yγ|y


(GeV)TE210×2 210×3 210×4 210×5 310

Theo

ry /

Data

0.5

1

1.5


T| < 1.5, pjet| < 2.5, |yγ1.57 < |y


(GeV)TE210×2 210×3 210×4 210×5 210×6

Theo

ry /

Data

0.5

1

1.5


T| < 2.4, pjet| < 2.5, 1.5 < |yγ1.57 < |y


Figure 7: Ratios of JETPHOX NLO predictions to data for various PDF sets as a function ofphoton ET for inclusive isolated-photons (top four panels) and photon+jets (four bottom pan-els). Data are shown as points, the error bars represent statistical uncertainties, while thehatched area represents the total experimental uncertainties. The theoretical uncertainty inthe NNPDF3.0 prediction is shown as a shaded area.

! Expect sensitivity to gluon PDFs over a wide range of (x,Q2)

! The ratio of the theoretical predictions to data with different PDF sets is studied. Observed differences are small, and within theoretical uncertainties.

! With precise NNLO calculations these measurements could be used to constraint the gluon and other PDFs.

Electroweak Z+2 jets

12

Properties of EW Zjj signal events:! well-separated jets in rapidity with large mjj, and central decay of Z boson! suppressed color flow in the region between the two jets (low hadronic

activity in the rapidity interval)

arXiv:1712.09814

EWK Z + 2 Jets

1

1 Introduction

In proton-proton (pp) collisions at the CERN LHC, the production of dileptons (``) consistentwith the Z boson invariant mass in association with two jets (jj) is dominated by events wherethe dilepton pair is produced by a Drell–Yan (DY) process, in association with jets from stronginteractions. This production is governed by a mixture of electroweak (EW) and strong pro-cesses of order a2

EWa2S, where aS is the strong coupling and aEW is the EW coupling strength.

The pure electroweak production of the ``jj final state, at order a4EW, is less frequent [1], and

includes production via the vector boson fusion (VBF) process, with its distinctive signatureof two jets with both large energy and separation in pseudorapidity h. In this paper the elec-troweak production is referred to as EW Zjj, and the two jets produced through the fragmenta-tion of the outgoing quarks are referred to as “tagging jets”.

Figure 1 shows representative Feynman diagrams for the EW Zjj signal, namely VBF (left),bremsstrahlung-like (center), and multiperipheral (right) production. Gauge cancellations leadto a large negative interference between the VBF process and the other two processes, with theinterferences from the bremsstrahlung-like production being larger. Interference with multi-peripheral production is limited to cases where the dilepton mass is close to the Z boson peakmass.

d u

W�

W+

Zµ+

µ�

u d

dZ

d

Z

d

µ+

µ�

u u

d u

W�

⌫̄µ

W+

µ�

µ+

u d

Figure 1: Representative Feynman diagrams for purely electroweak amplitudes for dileptonproduction in association with two jets: vector boson fusion (left), bremsstrahlung-like (center),and multiperipheral production (right).

In the inclusive production of ``jj final states, some of the nonexclusive EW interactions withidentical initial and final states can interfere with the exclusive EW interactions that are shownin Fig. 1. This interference effect between the signal production and the main backgroundprocesses is much smaller than the interference effects among the EW production amplitudes,but needs to be taken into account when measuring the signal contribution.

Figure 2 (left) shows one example of corrections to order a2S for DY production that have the

same initial and final states as those in Fig. 1. A process at order a2S that does not interfere with

the EW signal is shown in Fig. 2 (right).

The study of EW Zjj processes is part of a more general investigation of standard model (SM)vector boson fusion and scattering processes that include studies of Higgs boson production [2–4] and searches for physics beyond the SM [5]. When isolated from the backgrounds, the prop-erties of EW Zjj events can be compared with SM predictions. Probing the additional hadronicactivity in selected events can shed light on the modelling of additional parton radiation [6, 7],which is important for signal selection or vetoing of background events.

Higher-dimensional operators can generate anomalous trilinear gauge couplings (ATGCs) [8,9], so that the measurement of the coupling strengths provides an indirect search for newphysics at mass scales not directly accessible at the LHC.

Vector Boson Fusion Bremsstrahlung-like Multiperipheral Collision

Electroweak production:

Basic event selection:! pT(j) > 25 GeV; mjj > 120 GeV;

pT(l1/l2) > 30/20 GeV; m(ll)=91±15 GeV! BDT with many input observables for

signal extraction

! pp collisions 2016: 35.9/fb! The first observation for this process at

13 TeV

BDT variablesSeveral discriminating variables used to achieve the best separation between DYZ+2jet and EW Z+2jet signal.

Even

ts /

60 G

eV

1

10

210

310

410

510

610

(13 TeV)-135.9 fb

DielectronCMSDataVVTop quarkZ + jetsEW ZjjEW ZjjMC stat. unc.

Dielectron

(GeV)jjm0 500 1000 1500 2000 2500 3000D

ata

/ MC

- 1

-0.4-0.2

00.20.4 scale up/down

Rµ,

Fµ

JES up/down

Even

ts /

0.10

1

10

210

310

410

510

(13 TeV)-135.9 fb


Dielectron

|jjη∆|

0 1 2 3 4 5 6 7 8 9Dat

a / M

C -

1

-0.4-0.2


Rµ,

Fµ

JES up/down

Discriminating variables:

mjj , �⌘jj , R(phardT ), z⇤(Z),pTjj , quark/gluon likelihood(QGL) of the two tagging jets

R(phardT ) =|~pTj1+~pTj2+~pTZ |

|~pTj1 |+|~pTj2 |+|~pTZ |

y⇤ = yZ � 12 (yj1 + yj2)

z⇤ = y⇤

�yjj

Even

ts /

60 G

eV

1

10

210

310

410

510

610

(13 TeV)-135.9 fb

DimuonCMSDataVVTop quarkZ + jetsEW ZjjEW ZjjMC stat. unc.

Dimuon

(GeV)jjm0 500 1000 1500 2000 2500 3000D

ata

/ MC

- 1

-0.4-0.2


Rµ,

Fµ

JES up/down

Even

ts /

0.10

1

10

210

310

410

510

610 (13 TeV)-135.9 fb


Dimuon

|jjη∆|

0 1 2 3 4 5 6 7 8 9Dat

a / M

C -

1

-0.4-0.2


Rµ,

Fµ

JES up/down

MG5 aMC+ Pythia8:

EW Zjj (LO MG5 aMC)DY Zjj (NLO MG5 aMC)DY Zjj (LO MG5 aMC)

Good agreement betweendata and MC predictions

15


13

! Simultaneous fit of EW and QCD component in the signal (high BDT) and control (low BDT) regions

arXiv:1712.09814

EWK Z + 2 Jets12 6 Systematic uncertainties

Even

ts /

0.10

1

10

210

310

410

510

610 (13 TeV)-135.9 fb


Dielectron

BDT'0 0.5 1 1.5 2 2.5 3D

ata

/ MC

- 1

-0.4-0.2


Rµ,

Fµ

JES up/down

Even

ts /

0.10

1

10

210

310

410

510

610

(13 TeV)-135.9 fb


Dimuon

BDT'0 0.5 1 1.5 2 2.5 3D

ata

/ MC

- 1

-0.4-0.2


Rµ,

Fµ

JES up/down

Figure 7: Distributions for transformed BDT discriminants in dielectron (left) and dimuon(right) events. The contributions from the different background sources and the signal areshown stacked, with data points superimposed. The expected signal-only contribution is alsoshown as an unfilled histogram. The lower panels show the relative difference between thedata and expectations, as well as the uncertainty envelopes for JES and µF,R scale uncertainties.

6.1 Experimental uncertainties

The following experimental uncertainties are considered.

Integrated luminosity — A 2.5% uncertainty is assigned to the value of the integrated lumi-nosity [56].

Trigger and selection efficiencies — Uncertainties in the efficiency corrections based on con-trol samples in data for the leptonic trigger and offline selections amount to a total of2–3%, depending on the lepton pT and h for both the ee and µµ channels. These uncer-tainties are estimated by comparing the lepton efficiencies expected in simulation andmeasured in data with a tag-and-probe method [57].

Jet energy scale and resolution — The energy of the jets enters at the selection level and inthe computation of the kinematic variables used to calculate the discriminants. Thereforethe uncertainty in the JES affects both the expected event yields and the final shapes.The effect of the JES uncertainty is studied by scaling up and down the reconstructed jetenergy by pT- and h-dependent scale factors [50]. An analogous approach is used for theJER.

QGL discriminator — The uncertainty in the performance of the QGL discriminator is mea-sured using independent Z+jet and dijet data [53]. Shape variations corresponding to thefull data versus simulation differences are implemented.

Pileup — Pileup can affect the identification and isolation of the leptons or the corrected en-ergy of the jets. When jet clustering is performed, pileup can induce a distortion of thereconstructed dijet system because of the contamination from tracks and calorimetric de-posits. This uncertainty is evaluated by generating alternative distributions of the num-ber of pileup interactions, corresponding to a 5% uncertainty in the total inelastic pp crosssection at

ps = 13 TeV.

BDT variablesSeveral discriminating variables used to achieve the best separation between DYZ+2jet and EW Z+2jet signal.

Even

ts /

60 G

eV

1

10

210

310

410

510

610

(13 TeV)-135.9 fb


Dielectron

(GeV)jjm0 500 1000 1500 2000 2500 3000D

ata

/ MC

- 1

-0.4-0.2


Rµ,

Fµ

JES up/down

Even

ts /

0.10

1

10

210

310

410

510

(13 TeV)-135.9 fb


Dielectron

|jjη∆|

0 1 2 3 4 5 6 7 8 9Dat

a / M

C -

1

-0.4-0.2


Rµ,

Fµ

JES up/down

Discriminating variables:

mjj , �⌘jj , R(phardT ), z⇤(Z),pTjj , quark/gluon likelihood(QGL) of the two tagging jets

R(phardT ) =|~pTj1+~pTj2+~pTZ |

|~pTj1 |+|~pTj2 |+|~pTZ |

y⇤ = yZ � 12 (yj1 + yj2)

z⇤ = y⇤

�yjj

Even

ts /

60 G

eV

1

10

210

310

410

510

610

(13 TeV)-135.9 fb


Dimuon

(GeV)jjm0 500 1000 1500 2000 2500 3000D

ata

/ MC

- 1

-0.4-0.2


Rµ,

Fµ

JES up/down

Even

ts /

0.10

1

10

210

310

410

510

610 (13 TeV)-135.9 fb


Dimuon

|jjη∆|

0 1 2 3 4 5 6 7 8 9Dat

a / M

C -

1

-0.4-0.2


Rµ,

Fµ

JES up/down

MG5 aMC+ Pythia8:

EW Zjj (LO MG5 aMC)DY Zjj (NLO MG5 aMC)DY Zjj (LO MG5 aMC)

Good agreement betweendata and MC predictions

15

Discriminating observables used in BDT

Result: σ(EW lljj)=552±19(stat)±55(syst) fb MG5_aMC+PYTHIA 8: σ(SM LO EW Z(ll)+2-jets)=543±24 fb


14

arXiv:1712.09814

EWK Z + 2 Jets

)-2 (TeV2Λ/WWWc5− 0 5

)-2

(TeV

2Λ/

Wc

20−

0

20

Expected 68% CLExpected 95% CLExpected 99% CLObserved 95% CL

= 13 TeVs, -1L = 35.9 fbCMS

Z1

g∆-0.1 -0.05 0 0.05 0.1

Zλ

-0.02

0

0.02


CMS (13 TeV)-135.9 fb

Z1

g∆-0.1 -0.05 0 0.05 0.1

Zλ

-0.02

0

0.02


CMS (13 TeV)-135.9 fb

(GeV)TSoft H0 50 100 150 200 250

Gap

vet

o ef

ficie

ncy

0.2

0.4

0.6

0.8

1CMSBDT > 0.92Dilepton

(13 TeV)-135.9 fb

DataDY (MG5_aMC NLO + Pythia8)DY + EWK Zjj (MG5_aMC LO + Pythia8)DY + EWK Zjj (MG5_aMC LO + Herwig)

Gap veto efficiency: fraction of events with a measured gap activity below a given threshold! Data disfavour background only

predictions! Bkg+Signal model with Herwig

does much better at low gap activity values

! Limits on anomalous trilinear gauge couplings

! No evidence for aTGC is found. The most stringent constraints on cWWW to date are extracted

Conclusions

15

Z/W/γ+Jets• Differential cross section measurements are stringent tests of SM

predictions; high experimental precision• NLO essential to describe jet multiplicity, transverse momentum of

the leading jet and Z boson• Fixed order NNLO predictions available with significantly reduced

theory uncertainties for W/Z• γ+Jets: PDF constraints possible with measurements and improved

NNLO predictions

EWK Z+2jets• First observation of the EW Zjj production at 13 TeV

• 10% prec. of σ measurement; in agreement with SM prediction• stringent limits on aTGC and constraints on gap activity modelling

arXiv:1712.09814

EWK Z + 2 Jets

W+JetsPhys. Rev. D 96 (2017) 072005



Gustaf Hällströmin katu 2 P.O.Box 64 00014 University of Helsinki FINLAND

T +358-2-941 50564 [email protected] [email protected] voutila.web.cern.ch

UNIVERSITY OF HELSINKI AND

HELSINKI INSTITUTE OF PHYSICS

Dear Dr. Henning Kirschenmann,

I would like to offer you the position of a post-doctoral researcher in our CMS Experiment project at the Helsinki Institute of Physics, starting January 1st, 2017, and extending until the end of the current project on 31st December, 2018. The contract is extendible by 3 years (up to December 2021) by mutual agreement, assuming the approval of the CMS Experiment project into the next 3-year period.

Helsinki Institute of Physics coordinates the Finnish participation in the CERN experiments and is an inde-pendent research institute within University of Helsinki, which is among the top 100 universities world-wide [1]. Finland participates in the CMS experiment and has leading roles in the tracker upgrade, tracker align-ment, jet calibration and CMS OpenData. Our physics analyses cover topics varying from Charged Higgs searches and neutral Higgs searches to top quark mass measurements, b physics and jet physics.

Our CMS Experiment group is composed of two professors (prof. Paula Eerola, director of HIP; asst. prof. Mikko Voutilainen), three senior scientists (Kati Lassila-Perini, Sami Lehti, Tapio Lampen) and six PhD stu-dents (T. Järvinen, J. Pekkanen, J. Heikkilä, S. Laurila, J. Havukainen, H. Siikonen). We also enlist several emerita and adjoint scientists (J. Tuominiemi, T. Linden, L. Wendland, M. Kortelainen).

Your responsibilities would include physics analysis, experimental physics responsibilities and leadership within CMS experiment (we especially encourage shift captain work, JEC EPR and development of your leadership within JetMET), supervision and advising of graduate students (in particular on SUSY Higgs searches and top quark mass), organization of national and international workshops and conferences, and actively applying for available funding (e.g. foundations post-doc pool, Academy of Finland post-docs, uni-versity post-docs, as well as travel funding from various foundations). The position includes some outreach activities and 5% of teaching.

We offer:

• Nationally competitive salary (salary level 5/5, i.e. about 3500 €/month), which includes healthcare, social security and pension

• Up to 4-month transition period at CERN before moving to Finland (remuneration 1500 €/month)

• Travel budget of 5000 €/anno within the project budget constraints

• Removal expenses of up to 2000 €

We would like to hear back from you by November 29th, 2016, in order to be able to arrange the necessary paper work for next year in time for a January 1st—31st , 2017 start, given your positive reply.

Best regards,

Asst. prof. Mikko Voutilainen, Project leader of the CMS Experiment project at HIP University of Helsinki and Helsinki Institute of Physics In Helsinki on November 9th, 2016

[1] #91 (#96, #67) according to QS World University Ranking in 2016 (2015,2014).

Backup

Particle Flow (PF) approach

17

Position, momentum of charged particles : e±, π±, μ±

Silicon Tracker Electromagnetic Calorimeter

Position & ID, energy of e±,γ, π0

Hadron Calorimeter

Energy of hadrons : p, n, π±, K ..

Position & momentum of μ±

Muon Chambers

Particle Flow (PF) approach

18

W/Z jet multiplicity distributions (pre-unfolding)

19

7

Even

ts

10

210

310

410

510

610

710

810 ee dataZ/γ

∗→ e

+e−

t t VV Single topZ/γ

∗→ ττ

CMS

(13 TeV)-12.19 fb

| < 2.4jet

> 30 GeV, |yjetT

p (R = 0.4) jetsTkAnti-

jetsN 0≥ 1≥ 2≥ 3≥ 4≥ 5≥ 6≥

Sim

ulat

ion/

Dat

a

0.6

0.8

1

1.2

1.4

Even

ts

10

210

310

410

510

610

710

810 ee dataZ/γ

∗→ e

+e−


∗→ ττ

CMS

(13 TeV)-12.19 fb

| < 2.4jet

> 30 GeV, |yjetT


jetsN= 0 = 1 = 2 = 3 = 4 = 5 = 6

Sim

ulat

ion/

Dat

a

0.6

0.8

1

1.2

1.4

Even

ts

10

210

310

410

510

610

710

810 dataµµ Z/γ

∗→ μ

+μ−


∗→ ττ

CMS

(13 TeV)-12.19 fb

| < 2.4jet

> 30 GeV, |yjetT


jetsN 0≥ 1≥ 2≥ 3≥ 4≥ 5≥ 6≥

Sim

ulat

ion/

Dat

a

0.6

0.8

1

1.2

1.4

Even

ts

10

210

310

410

510

610

710

810 dataµµ Z/γ

∗→ μ

+μ−


∗→ ττ

CMS

(13 TeV)-12.19 fb

| < 2.4jet

> 30 GeV, |yjetT


jetsN= 0 = 1 = 2 = 3 = 4 = 5 = 6

Sim

ulat

ion/

Dat

a

0.6

0.8

1

1.2

1.4

Figure 1: Reconstructed data, simulated signal, and background distributions of the inclusive(left) and exclusive (right) jet multiplicity for the electron (upper) and muon (lower) channels.The background distributions are obtained from the simulation, except for the tt contributionwhich is estimated from the data as explained in the text. The error bars correspond to thestatistical uncertainty. In the ratio plots, they include both the uncertainties from data andfrom simulation. The set of generators described in Section 5 has been used for the simulation.

misidentification probability of approximately 1% for light-flavor jets with pT > 30 GeV. After the implementation ofthe b tag veto, the expected contributions from the back-ground processes and the observed data are given in Table Ias a function of the jet multiplicity. For jet multiplicitiesof 1–6, the b tag veto rejects 71%–88% of the predicted tt̄background and 5%–29% of the W þ jets signal.Differences in the data and simulation b tagging efficien-cies and mistagging rates are corrected by applying data-to-simulation scale factors [39].

VI. DATA-TO-SIMULATION COMPARISONS

The goal of this analysis is to measure the differentialcross sections characterizing the production of a W bosonand associated jets as functions of several kinematic andangular observables with 13 TeV data. We first comparedata with simulated processes at the reconstruction level forsome of the observables that are used for the cross sectionmeasurement. Signal and background processes in thesecomparisons are simulated with the event generatorsdescribed in Sec. III, with the exception of the QCDmultijet background, which is estimated using a datacontrol region with an inverted muon isolation requirement.In the data control region, the muon misidentification ratefor multijet processes is estimated in a sideband region withmT < 50 GeV and the multijet distribution shape templateis extracted in a region with mT > 50 GeV. The muonmisidentification rate is then used to rescale the multijetshape template. This estimation method was used in themeasurement of the W þ jets production cross section at7 TeV, and it is described in detail in Ref. [1].At high jet multiplicities, where the W þ jets signal is

less dominant, the accuracy of the background modelingbecomes more important, especially for the tt̄ productionprocess. We created a tt̄-enriched control sample byrequiring two or more b-tagged jets. The purity of thistt̄ control sample increases towards higher jet multiplicitiesand ranges between 79%–96% for jet multiplicities of 2–6.The differences between data and simulation observed for

jet multiplicities of 2–6 in the tt̄ control region areexpressed in terms of tt̄ data-to-simulation scaling factorsthat range between 0.75 and 1.15. The tt̄ background eventsare scaled by these factors in all the reconstructed-level andunfolded distributions presented in this paper for eventswith jet multiplicities of 2–6.The comparison of reconstructed distributions for data and

simulated processes is shown in Fig. 1 for the jet multiplicity.The pT distribution of the leading jet and the azimuthalcorrelation between the muon and the leading jet in events

= 0 = 1 = 2 = 3 = 4 = 5 = 6

Num

ber

of e

vent

s

10

210

310

410

510

610

710

810

910 VV QCD multijet Single t DY+jets

t t)+jetsνµ W(

Data

CMS

(13 TeV)-12.2 fb

| < 2.4jet

> 30 GeV, |yjet

Tp

jets, R = 0.4Tanti-k

jetsN= 0 = 1 = 2 = 3 = 4 = 5 = 6

Sim

ulat

ion/

Dat

a

0.6

0.8

1

1.2

1.4

FIG. 1. Data-to-simulation comparison as a function of the jetmultiplicity. The processes included are listed in Table I. TheQCD multijet background is estimated using control samples indata. The tt̄ background is scaled as discussed in Sec. VI. Theerror bars in the ratio panel represent the combined statisticaluncertainty of the data and simulation.

TABLE I. Numbers of events in simulation and data as a function of the exclusive jet multiplicity after the implementation of b tagveto. The processes included are: WW, WZ, and ZZ diboson (VV), QCD multijet, single top quark (Single t), Z=γ" þ jets Drell–Yan(DYþ jets), tt̄, and WðμνÞ þ jets signal processes. The QCD multijet background is estimated using control data samples. The tt̄background is scaled as discussed in Sec. VI.

Njets 0 1 2 3 4 5 6

VV 4302 1986 774 205 45 10 2QCD multijet 2 05 800 75 138 12 074 2556 612 53 5Single t 3392 5484 3277 1194 317 83 19DYþ jets 5 20 653 69 660 14 666 3041 643 133 33tt̄ 1663 4901 8084 6170 3152 1152 319WðμνÞ þ jets 12 171 400 1 601 858 3 26 030 64 484 11 736 2072 404

Total 12 907 210 1 759 027 3 64 905 77 650 16 505 3503 782

Data 12 926 230 1 680 182 3 49 480 73 817 16 866 3964 909


072005-4

electroweak and qcd aspects in v+jetsrabbertz/office/... · gustaf hällströmin katu 2 p.o.box 64...

Documents