Theoretical calculationsfor phenomenology at the LHC

Mathieu PELLEN

University of Freiburg

Group Leader Position at the Max Planck Institute for Physics

Max Planck Institute for Physics, Germany

26th of January 2021

Legacy of the LHC:

4−10

3−10

2−10

1−10

1

10

210

310

410

510 [pb]

σPr

oduc

tion

Cro

ss S

ectio

n,

CMS PreliminarySeptember 2020

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

W

n jet(s)≥

Z

n jet(s)≥

γW γZ WW WZ ZZ VVV WWW WWZ WZZ ZZZ γWV γγZ γγWµll, l=e,→, Zνl→: fiducial with Wγγ,WγγEW,Z

qqWEW qqZ

EWWW→γγ

γqqWEW

ssWW EW

γqqZEW

qqWZEW

qqZZEW tt

=n jet(s)

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

ggHqqHVBF VH WH ZH ttH tH 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 )-1 137 fb≤13 TeV CMS measurement (L

Theory prediction

Mathieu PELLEN Theoretical calculations for phenomenology at the LHC 2 / 22

Outline:

! Selection of ...

Physics results

source: ATLAS

Tools to obtain these results

source: www.nist.gov

! ... at the LHCMathieu PELLEN Theoretical calculations for phenomenology at the LHC 3 / 22

Exploring the Electroweak sectorof the Standard Model

pp ! W± + jc @ NNLO QCD

pp ! W+W�j @ NLO QCD+EW with parton shower

pp ! W±W±jj @ full NLO

Mathieu PELLEN Theoretical calculations for phenomenology at the LHC 4 / 22

1) pp ! W± + jc @ NNLO QCD

s̄

g

⌫µ

µ+

c̄

s

g

⌫̄µ

µ�

c

Direct link between W+c measurements and strange PDF

Study of flavour jets [Banfi, Salam, Zanderighi; hep-ph/0601139]

B First NNLO QCD computation of W+c-jet[Czakon, Mitov, MP, Poncelet; 2011.01011]

Mathieu PELLEN Theoretical calculations for phenomenology at the LHC 5 / 22

1) pp ! W± + jc @ NNLO QCD

s̄

g

⌫µ

µ+

c̄

s

g

⌫̄µ

µ�

c

Direct link between W+c measurements and strange PDF

Study of flavour jets [Banfi, Salam, Zanderighi; hep-ph/0601139]

B First NNLO QCD computation of W+c-jet[Czakon, Mitov, MP, Poncelet; 2011.01011]

Mathieu PELLEN Theoretical calculations for phenomenology at the LHC 5 / 22

1) pp ! W± + jc @ NNLO QCD

10 15 20 25 30 35 40 45 50 55

� [pb]

W�jc

W+jc

LHC 7 TeV PDF: NNPDF31 LONLO

NNLO

NNLO PDF unc.

ATLAS

0.80 0.85 0.90 0.95 1.00 1.05

RW±jc

[Czakon, Mitov, MP, Poncelet; 2011.01011]

Comparison against ATLAS data

Good overall agreementB PDF uncertainty dominant

Potential to improve understanding of strange within proton:! Strange asymmetry / Global PDF fit

Mathieu PELLEN Theoretical calculations for phenomenology at the LHC 6 / 22

2) pp ! W+W�j @ NLO QCD+EW with parton shower

q

q̄

e�

⌫̄eWµ+

⌫µW

g

q

g

e�

⌫̄eWµ+

⌫µW

q

Motivated by ATLAS measurement [1608.03086]

Search for anomalous triple gauge-boson couplings

Complementary to di-boson measurements! Similar e↵ect with di↵erent kinematic

Mathieu PELLEN Theoretical calculations for phenomenology at the LHC 7 / 22

2) pp ! W+W�j @ NLO QCD+EW with parton shower

q

q̄

e�

⌫̄eWµ+

⌫µW

g

q

g

e�

⌫̄eWµ+

⌫µW

q

Motivated by ATLAS measurement [1608.03086]

Search for anomalous triple gauge-boson couplings

Complementary to di-boson measurements! Similar e↵ect with di↵erent kinematic

Mathieu PELLEN Theoretical calculations for phenomenology at the LHC 7 / 22

2) pp ! W+W�j @ NLO QCD+EW with parton shower

njet = 1

She

rpa

+Re

co

la

MEPS@NLOpp ! µ+nµe�n̄epp ! + 0,1j@NLO + 2,3j@LO

LONLO QCDNLO QCD + EWapproxNLO QCD ⇥ EWapprox10

�2

10

�1

1

pp ! µ+nµe�n̄e + jets @ 13 TeV

ds/d

p T,j 1

[fb/

GeV

]

0 50 100 150 200 250 300 350 400

0.70.80.91.01.11.2

pT,j1 [GeV]

s/s

MEP

S@N

LOQ

CD

njet = 1

She

rpa

+Re

co

la

MEPS@NLO pp ! µ+nµe�n̄e + 0,1j@NLO + 2,3j@LO

LONLO QCD

NLO QCD + EWapproxNLO QCD ⇥ EWapprox

0

10

20

30

40

50

pp ! µ+nµe�n̄e + jets @ 13 TeVds

/dy j

1[f

b]

-2 -1 0 1 2

0.8

0.9

1.0

1.1

yj1

s/s

MEP

S@N

LOQ

CD

[Bräuer, Denner, MP, Schönherr, Schumann; 2011.01011]

Inclusion of EW e↵ects in NLO+Parton Shower simulation

Typical EW Sudakov logarithms

Mathieu PELLEN Theoretical calculations for phenomenology at the LHC 8 / 22

2) pp ! W+W�j @ NLO QCD+EW with parton shower

She

rpa

+Re

co

la

MEPS@NLO pp ! µ+nµe�n̄e + 0,1j@NLO + 2,3j@LO

LONLO QCD

NLO QCD + EWapproxNLO QCD ⇥ EWapprox

0

2

4

6

8

pp ! µ+nµe�n̄e + jets @ 13 TeV

R1j 0j

(pT,

mis

s)

0 50 100 150 200 250 300 350 400

0.9

1.0

1.1

pT,miss [GeV]

R1j 0j

/R

1j 0j,M

EPS@

NLO

QC

D

She

rpa

+Re

co

la

LONLO QCD

NLO QCD + EWapproxNLO QCD ⇥ EWapprox

MEPS@NLO pp ! µ+nµe�n̄e + 0,1j@NLO + 2,3j@LO

0.2

0.4

0.6

0.8

1

pp ! µ+nµe�n̄e + jets @ 13 TeV

R1j 0j

(Df

µ+

e�)

0 20 40 60 80 100 120 140 160 180

0.9

1.0

1.1

Dfµ+e� [�]

R1j 0j

/R

1j 0j,M

EPS@

NLO

QC

D

[Bräuer, Denner, MP, Schönherr, Schumann; 2011.01011]

Use of ratios WWj/WW! WW known up to NNLO + PS [Re, Wiesemann, Zanderighi; 1805.09857]! Cancellation of uncertainties! Sensitive probe of the Standard Model

Mathieu PELLEN Theoretical calculations for phenomenology at the LHC 9 / 22

3) pp ! W±W±jj @ full NLOVector-boson scattering and its background

W+

W+

H

u

d̄

d

ū

⌫ee+⌫µµ+

W+

W+

W+

W+

u

d̄

d

ū

⌫ee+⌫µµ+W

+

W+

u

d̄

g

d

ū

⌫ee+⌫µµ+

W+

W+

First full NLO computation for same-sign WW

B Already known:! approx. O(↵s↵6) [Jäger, Oleari, Zeppenfeld; 0907.0580], [Denner, Hošeková, Kallweit; 1209.2389]! O(↵3s↵4) [Melia, Melnikov, Röntsch, Zanderighi], [Campanario, Kerner, Ninh, Zeppenfeld; 1311.6738]

Mathieu PELLEN Theoretical calculations for phenomenology at the LHC 10 / 22

3) pp ! W±W±jj @ full NLOVector-boson scattering and its background

W+

W+

H

u

d̄

d

ū

⌫ee+⌫µµ+

W+

W+

W+

W+

u

d̄

d

ū

⌫ee+⌫µµ+W

+

W+

u

d̄

g

d

ū

⌫ee+⌫µµ+

W+

W+

O�↵s↵5�O�↵6� O�↵2s↵4

�LO

O�↵7� O�↵s↵6� O�↵2s↵5

� O�↵3s↵4�

NLO

EW

QCD

EW

QCD

EW

QCD

First full NLO computation for same-sign WW

B Already known:! approx. O(↵s↵6) [Jäger, Oleari, Zeppenfeld; 0907.0580], [Denner, Hošeková, Kallweit; 1209.2389]! O(↵3s↵4) [Melia, Melnikov, Röntsch, Zanderighi], [Campanario, Kerner, Ninh, Zeppenfeld; 1311.6738]

Mathieu PELLEN Theoretical calculations for phenomenology at the LHC 10 / 22

3) pp ! W±W±jj @ full NLOVector-boson scattering and its background

W+

W+

H

u

d̄

d

ū

⌫ee+⌫µµ+

W+

W+

W+

W+

u

d̄

d

ū

⌫ee+⌫µµ+W

+

W+

u

d̄

g

d

ū

⌫ee+⌫µµ+

W+

W+

O�↵s↵5�O�↵6� O�↵2s↵4

�LO

O�↵7� O�↵s↵6� O�↵2s↵5

� O�↵3s↵4�

NLO

EW

QCD

EW

QCD

EW

QCD

First full NLO computation for same-sign WW

B Already known:! approx. O(↵s↵6) [Jäger, Oleari, Zeppenfeld; 0907.0580], [Denner, Hošeková, Kallweit; 1209.2389]! O(↵3s↵4) [Melia, Melnikov, Röntsch, Zanderighi], [Campanario, Kerner, Ninh, Zeppenfeld; 1311.6738]Mathieu PELLEN Theoretical calculations for phenomenology at the LHC 10 / 22

3) pp ! W±W±jj @ full NLO

10�5

10�4

10�3

-30-25-20-15-10-505

10

-3-2-10123

600 800 1000 1200 1400 1600 1800 2000

dsdM

j 1j 2

⇥fb GeV⇤

LO EWLO QCDLO INTNLO

d[%

]

a7 asa6 NLO

d[%

]

Mj1j2 [GeV]

a2s a5 a3s a4 photon a7

dsdM

j 1j 2

⇥fb GeV⇤

LONLO

10�3

d[%

]

Mj1j2 [GeV]

-30-25-20-15-10-505

1015

600 800 1000 1200 1400 1600 1800 2000

[Biedermann, Denner, MP; 1708.00268]

Di↵erent LO and NLO behavioursB Large EW corrections

Mathieu PELLEN Theoretical calculations for phenomenology at the LHC 11 / 22

3) pp ! W±W±jj @ full NLO! O(↵7) reproduced by Leading-Log approximation

�LL = �LO

1 �

↵

4⇡4CewW log

2

Q2

M2W

!+

↵

4⇡2bewW log

Q2

M2W

!�

C ew larger for bosons than fermionshm4`i larger for VBS (massive t-channel [Denner, Hahn; hep-ph/9711302])

! Large EW corrections: intrinsic feature of VBS at the LHC

ds dyj 1

j 2[fb

]

LONLO EW

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

d[%

]

yj1j2

NLO EW-20

-15

-10

-5

0

-3 -2 -1 0 1 2 3

[Biedermann, Denner, MP; 1611.02951]

Sensitive to EW corrections at High-Luminosity LHC

Mathieu PELLEN Theoretical calculations for phenomenology at the LHC 12 / 22

At the core of this work:Development of methods and tools

All LHC results are obtained with computer programs!

All cutting edge computations requires huge CPU resources

Automation necessary to cover all LHC physics

Programs are a way to communicate results! Golden standard: automatised and public tools!

Mathieu PELLEN Theoretical calculations for phenomenology at the LHC 13 / 22

At the core of this work:Development of methods and tools

All LHC results are obtained with computer programs!

All cutting edge computations requires huge CPU resources

Automation necessary to cover all LHC physics

Programs are a way to communicate results! Golden standard: automatised and public tools!

Mathieu PELLEN Theoretical calculations for phenomenology at the LHC 13 / 22

NLO QCD/EW corrections in POWHEG

! Implementation process by process in POWHEG[Alioli, Frixione, Ježo, Nason, Oleari, Re; hep-ph/0409146, 0709.2092, 1002.2581, 1509.09071]

1) Squark production and decay at NLO SUSY QCD[Gavin, Hangst, Krämer, Mühlleitner, MP, Popenda, Spira; 1305.4061, 1407.7971]

2) Same-sign W-boson scattering at NLO EW[Chiesa, Denner, Lang, MP; 1906.01863]

Work

Implementation of all partonic/decay channels

Implementation of necessary pieces! Matrix elements, colour-correlated matrix elements, etc.! Either own subroutines or automatised code

Mathieu PELLEN Theoretical calculations for phenomenology at the LHC 14 / 22

NLO QCD/EW corrections in POWHEG

2) Same-sign W-boson scattering at NLO EW[Chiesa, Denner, Lang, MP; 1906.01863]

Interface with general matrix-element generator:Recola [Actis, Denner, Hofer, Lang, Scharf; 1605.01090]! Basis of general interface [Chiesa, Oleari, Re; 2005.12146]

O�↵s↵5�O�↵6� O�↵2s↵4

�LO

O�↵7� O�↵s↵6� O�↵2s↵5

� O�↵3s↵4�

NLO

EW

QCD

EW

QCD

EW

QCD

! To be used with other contributions available in POWHEG[Melia, Nason, Rontsch, Zanderighi; 1102.4846] [Jäger, Zanderighi; 1108.0864]

Mathieu PELLEN Theoretical calculations for phenomenology at the LHC 15 / 22

NNLO QCD corrections in StripperStripper:Implementation of sector-improved residue subtraction scheme

[Czakon, Heymes, Poncelet; 1005.0274, 1101.0642, 1408.2500]

! General framework for NNLO QCD computations! As POWHEG, implementation on a process-by-process basisMy work

Implementation of integration channel! mapping of resonanceInterface with OpenLoops2 [Buccioni, et al.; 1907.13071]

Implementation of two-loop virtual [Gehrmann, Tancredi; 1112.1531]! Convention matching with complex expressions! Evaluation of harmonic polylogarithms with ...... Ginac [Bauer, Frink, Kreckel], [Vollinga, Weinzierl; hep-ph/0410259]

! Outcome: NNLO QCD corrections for W+c-jet[Czakon, Mitov, MP, Poncelet; 2011.01011]

Mathieu PELLEN Theoretical calculations for phenomenology at the LHC 16 / 22

Automation of NLO QCD and EW in Sherpa

Sherpa: General multi-purpose Monte Carlo[Gleisberg, Höche, Krauss, Schönherr, Schälicke, Schumann, Siegert, Winter; hep-ph/0311263, 0811.4622]

[Biedermann, Bräuer, Denner, MP, Schumann, Thompson; 1704.05783]

General implementation of any NLO corrections! also mixed correctionsDesign of interface between Sherpa and Recola! C++ $ Fortran

Output

NLO corrections for any process

Use all functionalities of Sherpa along with NLO corrections

Applications:! t̄t, ZZ, V + jets [Biedermann, Bräuer, Denner, MP, Schumann, Thompson; 1704.05783]3-jets [Reyer, Schönherr, Schumann; 1902.01763], tri-bosons [Reyer, Schönherr, Schumann;1806.00307], WW/WWj [Bräuer, Denner, MP, Schönherr, Schumann; 2011.01011]

Mathieu PELLEN Theoretical calculations for phenomenology at the LHC 17 / 22

NLO QCD corrections in MadGraph5 aMC@NLO

! Automation NLO QCD for Dark-Matter simplified models[Backovic, Krämer, Maltoni, Martini, Mawatari, MP; 1508.05327]

Tool chain

FeynRules [Alloul et al.; 1310.1921]

NLOCT [Degrande; 1406.3030]

FeynArts [Hahn; hep-ph/0012260]

! NLO QCD UFO files [Degrande et al.; 1108.2040]: DMsimp

! Can be used for any process in MG5 aMC [Alwall et al.; 1405.0301]! Used extensively by both communities:

Experiment: for all Dark-Matter searches in ATLAS and CMS

Theory: [Haisch, Kahlhoefer, Tait; 1603.01267], [Asadi et al.; 1603.01267], ...

Mathieu PELLEN Theoretical calculations for phenomenology at the LHC 18 / 22

Development of MoCaNLO - past

MoCaNLO: Monte Carlo event generator for NLOcalculations of hadron-collider processes

! Multi-channel Monte Carlo written by Robert FegerMy work

Make it more general

NLO EW corrections! Treatment of mixed QCD-EW correctionsPole approximation at NLO QCD/EW! non-factorisable correctionsPerformance improvements

Further automation of the code

! E�cient for high-multiplicity processes (2 ! 6 and beyond)

Mathieu PELLEN Theoretical calculations for phenomenology at the LHC 19 / 22

Development of MoCaNLO - future

! Frontier of the code:pp ! µ�⌫̄µe+⌫eb̄bb̄b at NLO QCD(2 ! 8 scattering with ...... 6 external QCD particles)[Denner, Lang, MP; 2008.00918]

10�4

10�3

10�2

10�1

d�[fb]/

dm

b1b

2[G

eV]

LO

LODPA

NLO

NLODPA

8090

100110

NLO

k

LO

k�

1[%

] k = full k = DPA

0 200 400 600mb1b2 [GeV]

�10�5

05

kDPA

kfull

�1[

%]

k = LO k = NLO

Plan: Make it better and even more general

Implementation of FKS subtraction [Frixione, Kunszt, Signer; hep-ph/9512328]

Matching to parton shower! mixed QCD-EW correctionsUsable for new physics models

Making it public!

Mathieu PELLEN Theoretical calculations for phenomenology at the LHC 20 / 22

Partial summary

Focus

Implementation of higher-order corrections

Development of Monte Carlo programs

Skills

Knowledge of several programming languages

Experience in using HEP tools

Intensive use of High-performance computing

Experience in maintaining codes

! Research mainly focused on LHC physics but ...... tools can be used in other fields e.g. Astroparticle physics[Ali Cavasonza, Krämer, MP; 1409.8226], [Ali Cavasonza, Gast, Krämer, MP, Schael; 1612.06634]

... also interest in numerical general relativity[Di Menza, Nicolas, MP; 1903.02941]

Mathieu PELLEN Theoretical calculations for phenomenology at the LHC 21 / 22

Partial summary

Focus

Implementation of higher-order corrections

Development of Monte Carlo programs

Skills

Knowledge of several programming languages

Experience in using HEP tools

Intensive use of High-performance computing

Experience in maintaining codes

! Research mainly focused on LHC physics but ...... tools can be used in other fields e.g. Astroparticle physics[Ali Cavasonza, Krämer, MP; 1409.8226], [Ali Cavasonza, Gast, Krämer, MP, Schael; 1612.06634]

... also interest in numerical general relativity[Di Menza, Nicolas, MP; 1903.02941]

Mathieu PELLEN Theoretical calculations for phenomenology at the LHC 21 / 22

Partial summary

Focus

Implementation of higher-order corrections

Development of Monte Carlo programs

Skills

Knowledge of several programming languages

Experience in using HEP tools

Intensive use of High-performance computing

Experience in maintaining codes

! Research mainly focused on LHC physics but ...... tools can be used in other fields e.g. Astroparticle physics[Ali Cavasonza, Krämer, MP; 1409.8226], [Ali Cavasonza, Gast, Krämer, MP, Schael; 1612.06634]

... also interest in numerical general relativity[Di Menza, Nicolas, MP; 1903.02941]

Mathieu PELLEN Theoretical calculations for phenomenology at the LHC 21 / 22

General summary

Theoretical calculations for phenomenology at the LHC

Exploring the Electroweak sector of the Standard Model! several examples of recent computations

Development of methods and tools for LHC phenomenology! several examples of tools developed

Thank you

Mathieu PELLEN Theoretical calculations for phenomenology at the LHC 22 / 22

General summary

Theoretical calculations for phenomenology at the LHC

Exploring the Electroweak sector of the Standard Model! several examples of recent computations

Development of methods and tools for LHC phenomenology! several examples of tools developed

Thank you

Mathieu PELLEN Theoretical calculations for phenomenology at the LHC 22 / 22

Back-up slides

BACK-UP

Mathieu PELLEN Theoretical calculations for phenomenology at the LHC 23 / 22