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Full NLO corrections to 3-jet production and R 32 at the LHC Max - - PowerPoint PPT Presentation

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Full NLO corrections to 3-jet production and R 32 at the LHC Max Reyer University of Freiburg (University of G ottingen) Eur. Phys. J. C79 no. 4, (2019) 321 arXiv:1902.01763 [hep-ph] In collaboration with Steffen Schumann Marek Sch

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SLIDE 1

Full NLO corrections to 3-jet production and R32 at the LHC

Max Reyer University of Freiburg (University of G¨

  • ttingen)
  • Eur. Phys. J. C79 no. 4, (2019) 321

arXiv:1902.01763 [hep-ph] In collaboration with Steffen Schumann Marek Sch¨

  • nherr

Loopfest XVIII @ Fermilab August 13th, 2019

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SLIDE 2

Outline

Motivation EW NLO Calculation Setup 3/2jet Production Results and R32

Full NLO corrections to 3-jet production and R32 at the LHC Max Reyer (Univ. Freiburg) 1/14

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SLIDE 3

Motivation

jet production:

  • most abundant process at LHC

⇒ allows multi-differential measurements into high-pT regions ⇒ benchmark for theoretical predictions

  • important SM background to many analyses
  • pure jet final state is BSM search ground

⇒ enhancements in high pT-tails

  • determination of PDFs and αs at high Q2

⇒ consistency check of RGE evolution over large range of scales

EW corrections:

  • naˆ

ıve relative magnitude of α ∼ 1% to inclusive XS

  • weak Sudakov logarithms ⇒ O (10%) corr in TeV range

⇒ inclusion necessitated by high pT reach

  • many subprocesses, all dipole kinematics and types involed

⇒ strong test case for automized NLO tools

Full NLO corrections to 3-jet production and R32 at the LHC Max Reyer (Univ. Freiburg) 2/14

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SLIDE 4

Previous Studies of Jet Production

  • NLO QCD up to 5 final state jets

[Ellis et al., 1992] [Giele et al., 1993] [Nagy, 2003] [Bern et al., 2012] [Badger et al., 2014]

  • NLO QCD combined with parton showers

[Alioli et al., 2011] [H¨

  • che et al., 2012]
  • NNLO QCD dijet completed

[Currie et al., 2016] [Currie et al., 2017] [Ridder et al., 2019] [Czakon et al., 2019] (full color)

  • pure weak corrections for dijet (no γ; O
  • α2

sα

  • , O (αsα), O
  • α2

)

[Dittmaier et al., 2012]

  • full SM NLO for dijet

[Frederix et al., 2017]

  • full SM NLO for 3jet, inclusive cross section

[Frederix et al., 2018]

here: full SM NLO for 3/2jet, (double) differential in Sherpa

Full NLO corrections to 3-jet production and R32 at the LHC Max Reyer (Univ. Freiburg) 3/14

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SLIDE 5

Features of EW NLO

Massless photons γ:

  • IR divergences necessitate

subtraction ⇒ descends from QCD via ˆ T(ij) ˆ Tk → Q(ij)Qk

  • add γ to jet clustering

Massive W ± and Z:

  • real emission distinct process class
  • IR finite loop contributions:

∼ α log2 Q2 m2

  • ,

⇒ Sudakov logs ∼ 10% @ 1TeV

  • unambiguous definition of NLO correction by perturbative order:

αn

s αm

αn−1

s

αm αn

s αm−1

Q C D N L O E W N L O

⇒ simultaneous QCD and QED subtraction with distinct underlying Borns X + g + γ final state X + g X + γ

Q E D s u b t r . QCD subtr.

⇒ forces γ in process definition

  • photon jet removal desired, requires e.g. fragmentation functions

Full NLO corrections to 3-jet production and R32 at the LHC Max Reyer (Univ. Freiburg) 4/14

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SLIDE 6

Automation of EW NLO

  • public full SM one-loop provider are becoming available
  • Recola
  • OpenLoops2
  • GoSam

⇒ paving road for automatic SM NLO event generator ⇒ already public: MadGraph5 aMC@NLO [Frederix et al., 2018] ⇒ still-private version of Sherpa [Sch¨

  • nherr, 2018]
  • bookkeeping in mixed coupling scenario
  • tree level ME
  • simultaneous QCD&QED subtraction: dipole terms, I-operators, ...
  • (approximate) procedures for combination with PS

Validated in growing set of processes Sherpa + OpenLoops

  • V + jets [Kallweit et al., 2015]

[Kallweit et al., 2016]

  • 2ℓ2ν

[Kallweit et al., 2017]

  • t¯

t + jets

[G¨ utschow et al., 2018] (approximate multijet merging)

Sherpa + GoSam

  • γγW and γγZ [Greiner et al.]
  • γγj [Chiesa et al.]

Sherpa + Recola

  • V + j, t¯

tH, e+e−µ+µ−

[Biedermann et al., 2017]

  • off-shell WWW [Sch¨
  • nherr, 2018]

Full NLO corrections to 3-jet production and R32 at the LHC Max Reyer (Univ. Freiburg) 5/14

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SLIDE 7

Calculation Setup - Process Definition

  • partonic processes

[ewj ∈ {q, g, γ, l, ν} → no external W , Z!] 3jet : ewj + ewj → ewj + ewj + ewj (+ewj), 2jet : ewj + ewj → ewj + ewj (+ewj),

  • perturb. orders αn

s αm

3jet : m + n = 3, 4 2jet : m + n = 2, 3,

  • sensitive to full SM spectrum (tops, Higgs, . . . )

O(α4

s)

O(α3

sα)

O(α2

sα2)

O(αsα3) O(α4)

Full NLO corrections to 3-jet production and R32 at the LHC Max Reyer (Univ. Freiburg) 6/14

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SLIDE 8

Calculation Setup - Input and Observable

  • Sherpa interfaced to Recola
  • pp @ 13 TeV,

PDF: NNPDF31 nlo as 0118 luxqed

  • scale choice µR = µF = 1

2 ˆ

HT ⇒ missing higher orders estimated by 7 point scale variation

  • Gµ scheme

⇒ mass logs from γ → f ¯ f splittings absorbed

  • complex mass scheme

jet def and fiducial phase space cuts:

  • 3 resp. 2 democratic anti-kT jets with R = 0.4 and

[no ν!] |η| < 2.8; p1

T ≥ 80GeV,

pi≥2

T

≥ 60GeV

  • reject ’lepton jets’: |ηj| < 2.5 and net lepton number

⇒ collinear same-flavor lepton pairs survive (IR safety!) ⇒ leptons outside tracker survive

Full NLO corrections to 3-jet production and R32 at the LHC Max Reyer (Univ. Freiburg) 7/14

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SLIDE 9

XS Nomenclature

  • nomenclature for n-jet XS:

O

  • σLOi

nj

  • = αn−i

s

αi, O

  • σ∆NLOi

nj

  • = αn+1−i

s

αi,

  • combination of QCD and EW NLO:

additive: σNLO QCD+EW

nj

= σLO0

nj

+ σ∆NLO0

nj

+ σ∆NLO1

nj

multiplicative: σNLO QCD×EW

nj

= σLO0

nj

  • 1 +

σ∆NLO0

nj

σLO0

nj

1 + σ∆NLO1

nj

σLO0

nj

  • estimate of unknown O(αsα) NNLO corrections:

σNLO

QCD×EW − σNLO QCD+EW = δσNLO QCD × δσNLO EW

σLO

Full NLO corrections to 3-jet production and R32 at the LHC Max Reyer (Univ. Freiburg) 8/14

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SLIDE 10

pT-Spectra

10

8

10

6

10

4

10

2

100 102 d /dp1

T [pb/GeV]

LO QCD NLO QCD NLO QCD+EW NLO QCD×EW full NLO p1

T, 3j

|

i| < 2.8

p1

T > 80 GeV

p2, 3

T

> 60 GeV 500 1000 1500 2000 2500 3000 3500 4000 p1

T [GeV]

0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.25 Ratio over NLO QCD 10

8

10

6

10

4

10

2

100 102 d /dp2

T [pb/GeV]

LO QCD NLO QCD NLO QCD+EW NLO QCD×EW full NLO p2

T, 3j

|

i| < 2.8

p1

T > 80 GeV

p2, 3

T

> 60 GeV 500 1000 1500 2000 2500 3000 3500 4000 p2

T [GeV]

0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.25 2.50 2.75 Ratio over NLO QCD 10

8

10

6

10

4

10

2

100 102 d /dp3

T [pb/GeV]

LO QCD NLO QCD NLO QCD+EW NLO QCD×EW full NLO p3

T, 3j

|

i| < 2.8

p1

T > 80 GeV

p2, 3

T

> 60 GeV 500 1000 1500 2000 p3

T [GeV]

0.50 0.75 1.00 1.25 1.50 1.75 Ratio over NLO QCD

  • large negative Sudakov-type EW NLO corrections

⇒ grow with i in pi

T (−10%, −15%, −15% at 2TeV)

  • scale uncertainties asymmetric, grow from QCD to QCD+EW
  • accidental cancellation with subleading LO and NLO contributions
  • mainly ∆NLO2, LO1, LO2
  • grow larger than ∆NLO1 for pT > 2.5TeV

⇒ highly dependent on observable & fiducial phase space

Full NLO corrections to 3-jet production and R32 at the LHC Max Reyer (Univ. Freiburg) 9/14

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SLIDE 11

pT-Spectra

10

11

10

9

10

7

10

5

10

3

10

1

101 103 d /dp1

T [pb/GeV]

LO0(

3 s )

LO1(

2 s 1)

LO2(

1 s 2)

LO3(

3)

NLO0(

4 s )

NLO1(

3 s 1)

NLO2(

2 s 2)

NLO3(

1 s 3)

NLO4(

4)

full NLO p1

T, 3j

|

i| < 2.8

p1

T > 80 GeV

p2, 3

T

> 60 GeV 500 1000 1500 2000 2500 3000 3500 4000 p1

T [GeV]

10

5

10

4

10

3

10

2

10

1

100 Ratio over full NLO 10

11

10

9

10

7

10

5

10

3

10

1

101 103 d /dp2

T [pb/GeV]

LO0(

3 s )

LO1(

2 s 1)

LO2(

1 s 2)

LO3(

3)

NLO0(

4 s )

NLO1(

3 s 1)

NLO2(

2 s 2)

NLO3(

1 s 3)

NLO4(

4)

full NLO p2

T, 3j

|

i| < 2.8

p1

T > 80 GeV

p2, 3

T

> 60 GeV 500 1000 1500 2000 2500 3000 3500 4000 p2

T [GeV]

10

4

10

3

10

2

10

1

100 Ratio over full NLO 10

11

10

9

10

7

10

5

10

3

10

1

101 d /dp3

T [pb/GeV]

LO0(

3 s )

LO1(

2 s 1)

LO2(

1 s 2)

LO3(

3)

NLO0(

4 s )

NLO1(

3 s 1)

NLO2(

2 s 2)

NLO3(

1 s 3)

NLO4(

4)

full NLO p3

T, 3j

|

i| < 2.8

p1

T > 80 GeV

p2, 3

T

> 60 GeV 500 1000 1500 2000 p3

T [GeV]

10

4

10

3

10

2

10

1

100 Ratio over full NLO

  • large negative Sudakov-type EW NLO corrections

⇒ grow with i in pi

T (−10%, −15%, −15% at 2TeV)

  • scale uncertainties asymmetric, grow from QCD to QCD+EW
  • accidental cancellation with subleading LO and NLO contributions
  • mainly ∆NLO2, LO1, LO2
  • grow larger than ∆NLO1 for pT > 2.5TeV

⇒ highly dependent on observable & fiducial phase space

Full NLO corrections to 3-jet production and R32 at the LHC Max Reyer (Univ. Freiburg) 9/14

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SLIDE 12

R32 Observable

R32(H(2)

T ) = dσ3j/dH(2) T

dσ2j/dH(2)

T

  • reduced experimental uncertainties

⇒ e.g. luminosity, jet energy scale

  • factorizing contributions in theory predictions cancel
  • strongly dependent on αs(H(2)

T )

⇒ allows for measurement [Chatrchyan et al., 2013] (fit of theory predictions to data) ⇒ consistency check of RGE evolution at high scales ⇒ possibly sensitive to BSM physics [Becciolini et al.]

  • sensitive to gluon PDF

Full NLO corrections to 3-jet production and R32 at the LHC Max Reyer (Univ. Freiburg) 10/14

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SLIDE 13

Input Distributions to R32

10

6

10

4

10

2

100 102 104 d /dH(2)

T [pb/GeV]

LO QCD NLO QCD NLO QCD+EW NLO QCD×EW full NLO H(2)

T , 2j

|

i| < 2.8

p1

T > 80 GeV

p2

T > 60 GeV

500 1000 1500 2000 2500 3000 3500 4000 4500 5000 H(2)

T [GeV]

0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.25 Ratio over NLO QCD 10

6

10

4

10

2

100 102 104 d /dH(2)

T [pb/GeV]

LO QCD NLO QCD NLO QCD+EW NLO QCD×EW full NLO H(2)

T , 3j

|

i| < 2.8

p1

T > 80 GeV

p2, 3

T

> 60 GeV 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 H(2)

T [GeV]

0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.25 Ratio over NLO QCD

  • in 3jet sample: at high H(2)

T

3rd jet predominantly soft ⇒ factorizing higher order corrections ⇒ similar EW corrections in 2jet and 3jet sample

Full NLO corrections to 3-jet production and R32 at the LHC Max Reyer (Univ. Freiburg) 11/14

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SLIDE 14

R32 Result

0.2 0.4 0.6 0.8 R32 LO QCD NLO QCD NLO QCD+EW NLO QCD×EW full NLO R32 for H(2)

T

|

i| < 2.8

p1

T > 80 GeV

p2, 3

T

> 60 GeV 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 H(2)

T [GeV]

0.50 0.75 1.00 1.25 1.50 Ratio over NLO QCD

  • small EW NLO and subleading order

corrections

  • factorization of EW corrections in

input distributions ⇒ beyond accidental cancellation ⇒ stable w.r.t add cuts on η := |η1 − η2|/2

  • correlated scale variation in ratio

⇒ much larger bands in 3jet ⇒ no cancellation of scale uncert.

Full NLO corrections to 3-jet production and R32 at the LHC Max Reyer (Univ. Freiburg) 12/14

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SLIDE 15

Dependence on η := |η1 − η2|/2

2jet

500 1000 1500 2000 2500 3000 3500 4000 4500 5000 H(2)

T

[GeV] 0.80 0.85 0.90 0.95 1.00 1.05 1.10 1.15 1.20 Ratio over NLO QCD H(2)

T , 2j

0.0 < < 0.5 p1

T > 80 GeV

p2

T > 60 GeV

NLO QCD NLO QCD+EW full NLO NLO QCD+EW + LO1 NLO QCD+EW + LO1 + LO2 500 1000 1500 2000 2500 H(2)

T [GeV]

0.80 0.85 0.90 0.95 1.00 1.05 1.10 1.15 1.20 Ratio over NLO QCD H(2)

T , 2j

1.0 < < 1.5 p1

T > 80 GeV

p2

T > 60 GeV

500 1000 H(2)

T [GeV]

0.80 0.85 0.90 0.95 1.00 1.05 1.10 1.15 1.20 Ratio over NLO QCD H(2)

T , 2j

2.0 < < 2.5 p1

T > 80 GeV

p2

T > 60 GeV

3jet

500 1000 1500 2000 2500 3000 3500 4000 4500 5000 H(2)

T

[GeV] 0.80 0.85 0.90 0.95 1.00 1.05 1.10 1.15 1.20 Ratio over NLO QCD H(2)

T , 3j

0.0 < < 0.5 p1

T > 80 GeV

p2, 3

T

> 60 GeV

0.0 < < 0.5

500 1000 1500 2000 2500 H(2)

T

[GeV] 0.80 0.85 0.90 0.95 1.00 1.05 1.10 1.15 1.20 Ratio over NLO QCD H(2)

T , 3j

1.0 < < 1.5 p1

T > 80 GeV

p2, 3

T

> 60 GeV

1.0 < < 1.5

500 1000 H(2)

T

[GeV] 0.80 0.85 0.90 0.95 1.00 1.05 1.10 1.15 1.20 Ratio over NLO QCD H(2)

T , 3j

2.0 < < 2.5 p1

T > 80 GeV

p2, 3

T

> 60 GeV

2.0 < < 2.5

R32

500 1000 1500 2000 2500 3000 3500 4000 4500 5000 H(2)

T [GeV]

0.80 0.85 0.90 0.95 1.00 1.05 1.10 1.15 1.20 Ratio over NLO QCD R32 for H(2)

T

0.0 < < 0.5 p1

T > 80 GeV

p2, 3

T

> 60 GeV 500 1000 1500 2000 2500 H(2)

T [GeV]

0.80 0.85 0.90 0.95 1.00 1.05 1.10 1.15 1.20 Ratio over NLO QCD R32 for H(2)

T

1.0 < < 1.5 p1

T > 80 GeV

p2, 3

T

> 60 GeV 500 1000 H(2)

T [GeV]

0.80 0.85 0.90 0.95 1.00 1.05 1.10 1.15 1.20 Ratio over NLO QCD R32 for H(2)

T

2.0 < < 2.5 p1

T > 80 GeV

p2, 3

T

> 60 GeV

Full NLO corrections to 3-jet production and R32 at the LHC Max Reyer (Univ. Freiburg) 13/14

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SLIDE 16

Summary

  • EW NLO corrections at high pT competitive with QCD NLO
  • Automated EW NLO MC generators are becoming available
  • Sherpa + Recola/OpenLoops/GoSam validated for many processes
  • accidental cancellations in H(2)

T -distributions

  • EW NLO corrections largely cancel in R32 of H(2)

T

Outlook:

  • Multijet merging in EWvirt-approximation:

[Kallweit et al., 2016]

dσNLO EWvirt = [B(Φn) + VEW(Φn) + IEW(Φn)] dΦn ⇒ No double counting issue ⇒ EW-NLO accurate multijet merging w/ LO complexity

  • Studies of photon jet removal and fragmentation functions Dq→γ, Dγ→had
  • Impact of initial state γ

Full NLO corrections to 3-jet production and R32 at the LHC Max Reyer (Univ. Freiburg) 14/14

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SLIDE 17

Summary

  • EW NLO corrections at high pT competitive with QCD NLO
  • Automated EW NLO MC generators are becoming available
  • Sherpa + Recola/OpenLoops/GoSam validated for many processes
  • accidental cancellations in H(2)

T -distributions

  • EW NLO corrections largely cancel in R32 of H(2)

T

Outlook:

  • Multijet merging in EWvirt-approximation:

[Kallweit et al., 2016]

dσNLO EWvirt = [B(Φn) + VEW(Φn) + IEW(Φn)] dΦn ⇒ No double counting issue ⇒ EW-NLO accurate multijet merging w/ LO complexity

  • Studies of photon jet removal and fragmentation functions Dq→γ, Dγ→had
  • Impact of initial state γ

Thank you!

Full NLO corrections to 3-jet production and R32 at the LHC Max Reyer (Univ. Freiburg) 14/14

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SLIDE 18

BACKUP: Masses

  • masses set to

Gµ = 1.16639 × 10−5 GeV−2 mW = 80.385 GeV ΓW = 2.085 GeV mZ = 91.1876 GeV ΓZ = 2.4952 GeV mh = 125.0 GeV Γh = 0.00407 GeV mt = 173.21 GeV Γt = 1.3394 GeV .

  • complex mass scheme:

µ2

i = m2 i − imiΓi

and sin2 θw = 1 − µ2

W

µ2

Z

,

  • all other particles massless

Full NLO corrections to 3-jet production and R32 at the LHC Max Reyer (Univ. Freiburg) 15/14

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SLIDE 19

BACKUP: Fiducial XS Tables

NLO

LO0 NLO LO1 NLO LO2 NLO LO3 NLO

[nb] [%] [%] [%] [%] σ2j 3385(3) 67.34(6) 0.0713(1) 0.03915(4) – σ3j 169(1) 148(1) 0.293(2) 0.196(2) 0.00217(2)

∆NLO0 NLO ∆NLO1 NLO ∆NLO2 NLO ∆NLO3 NLO ∆NLO4 NLO

[%] [%] [%] [%] [%] σ2j 32.59(8) −0.118(7) 0.0759(3) 0.00022(1) – σ3j −48.4(8) −0.74(1) 0.344(7) −0.00433(6) 0.0135(2) Full fiducial XS NLO

LO0 NLO LO1 NLO LO2 NLO LO3 NLO

[fb] [%] [%] [%] [%] σ2j 51.9(6) 60(1) 7.07(8) 1.82(2) – σ3j 40.0(4) 99(1) 8.6(1) 2.05(4) 0.061(1)

∆NLO0 NLO ∆NLO1 NLO ∆NLO2 NLO ∆NLO3 NLO ∆NLO4 NLO

[%] [%] [%] [%] [%] σ2j 36.9(8) −4.5(1) −1.02(2) −0.552(7) – σ3j −0.9(9) −9.8(4) 1.09(7) 0.057(4) 0.314(5) Fiducial XS after additional leading jet cut p1

T > 2TeV Full NLO corrections to 3-jet production and R32 at the LHC Max Reyer (Univ. Freiburg) 16/14

slide-20
SLIDE 20

BACKUP: Fiducial XS Tables

NLO LO QCD NLO QCD NLO EW NLO QCD + EW [nb] [nb] [nb] [nb] [nb] σ2j 3385(3)+334

−338

2279.4(6)+553.7

−404.4

3383(3)+335

−338

2275.4(6)+552.4

−403.5

3379(3)+333

−338

σ3j 169(1)+16

−73

249.86(6)+102.28

−67.89

168(1)+16

−73

248.62(6)+101.62

−67.46

167(1)+17

−73

Full fiducial XS NLO LO QCD NLO QCD NLO EW NLO QCD + EW [fb] [fb] [fb] [fb] [fb] σ2j 51.9(6)+5.9

−6.7

31.2(5)+11.4

−7.9

50.4(6)+7.1

−7.3

28.9(5)+9.6

−6.7

48.1(6)+5.2

−6.1

σ3j 40.0(4)+0.4

−6.9

39.4(2)+19.0

−12.1

39.0(4)+0.0

−5.0

35.5(2)+15.7

−10.2

35.1(4)+0.9

−8.2

Fiducial XS after additional leading jet cut p1

T > 2TeV

Full NLO corrections to 3-jet production and R32 at the LHC Max Reyer (Univ. Freiburg) 17/14