New physics simulations
From Lagrangians to events… and back

Benjamin Fuks
(LPTHE - Sorbonne Université)

Iwate Collider School 2023 (Appi, Iwate)
27 February − 4 March 2023
New physics simulations − From Lagrangians to events and back

Benjamin Fuks - 01.03.2023 - 1

Outline1.

A comprehensive approach for Monte Carlo simulations

2.

Implementing models into Monte Carlo event generators

3.

From events to Lagrangian: reinterpretation of the results of the LHC

4.

Summary

New physics simulations − From Lagrangians to events and back

Benjamin Fuks - 01.03.2023 - 2

MC simulations & new physics
Towards the characterisation of new physics• About the nature of an observation➙ Fitting and (re)interpreting deviations➙ Prospective collider studies of varied signals

Goal of all lectures atthis school• Final words on the nature of any potential BSM➙ Accurate measurements➙ Precise predictions mandatory

New physics simulations − From Lagrangians to events and back

Benjamin Fuks - 01.03.2023 - 3

MC simulations & new physics
Towards the characterisation of new physics• About the nature of an observation➙ Fitting and (re)interpreting deviations➙ Prospective collider studies of varied signals

Goal of all lectures atthis school• Final words on the nature of any potential BSM➙ Accurate measurements➙ Precise predictions mandatory

New physics simulations standard today• 20 − 25 years of developments ➙ LO simulations ≡ bread and butter• Simulations at NLO (QCD) easily achieved
Idea
Lagrangian

Chain oftools

Simulatedcollisions

Other
tools

Event
analysis

L = LSM⇥⇤+ Tr Dµ ˆ † Dµ ˆ
Y L̄ · ˆ L + H.c.
V (', ˆ )<latexit sha1_base64="5CPsatWeguRhSwWV/BdmxRLZKZM=">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</latexit>

Any model Easy validation

New physics simulations − From Lagrangians to events and back

Benjamin Fuks - 01.03.2023 - 3

[ A SHERPA artist ]Deciphering a proton collision

Proton

New physics simulations − From Lagrangians to events and backProtonBenjamin Fuks - 01.03.2023 - 4

Deciphering a proton collision
Hard process[ A SHERPA artist ]• Depends on the model (SM/BSM)• Perturbative QCD• Core #1 of this talkProton

New physics simulations − From Lagrangians to events and backProtonBenjamin Fuks - 01.03.2023 - 4

Deciphering a proton collision
Hard process[ A SHERPA artist ]• Depends on the model (SM/BSM)• Perturbative QCD• Core #1 of this talk
Parton showering• Universal (QCD)

Proton

New physics simulations − From Lagrangians to events and backProtonBenjamin Fuks - 01.03.2023 - 4

Deciphering a proton collision
Hard process[ A SHERPA artist ]• Depends on the model (SM/BSM)• Perturbative QCD• Core #1 of this talk
Parton showering• Universal (QCD)
Hadronisation• Model-based, universal

Underlying event• Model-based, non-universal
Proton

New physics simulations − From Lagrangians to events and backProtonBenjamin Fuks - 01.03.2023 - 4

Deciphering a proton collision
Hard process[ A SHERPA artist ]• Depends on the model (SM/BSM)• Perturbative QCD• Core #1 of this talk
Parton showering• Universal (QCD)
Hadronisation• Model-based, universal

Underlying event• Model-based, non-universal
Proton

New physics simulations − From Lagrangians to events and backProtonDetector simulation

Benjamin Fuks - 01.03.2023 - 4

Deciphering a proton collision
Hard process[ A SHERPA artist ]• Depends on the model (SM/BSM)• Perturbative QCD• Core #1 of this talk
Parton showering• Universal (QCD)
Hadronisation• Model-based, universal

Underlying event• Model-based, non-universal
ProtonProtonDetector simulation

Multiscale problem➙ factorisation➙ one tool / step
New physics simulations − From Lagrangians to events and back

Benjamin Fuks - 01.03.2023 - 4

SM and BSM simulations: the status
SM simulations under good control• Relevant LHC processes: known with a very good precision• Further improvements expected in the next few years

New physics simulations − From Lagrangians to events and back

Benjamin Fuks - 01.03.2023 - 5

SM and BSM simulations: the status
SM simulations under good control• Relevant LHC processes: known with a very good precision• Further improvements expected in the next few years

Different challenges for new physics• No sign of new physics• SM-like measurements➙ no leading candidate theory• Plethora of models to consider➙ many implementations in tools
Despite of this, newphysics is standard today[ Tait ]New physics simulations − From Lagrangians to events and back

Benjamin Fuks - 01.03.2023 - 5

Connecting ideas to simulations…
[ Christensen, de Aquino, Degrande, Duhr, BF, Herquet, Maltoni & Schumann (EPJC`11) ]• Model building
Idea / Lagrangian• Hard scattering

Feynman diagram and amplitude generation★ Monte Carlo integration★ Event generation★

FEYNRULES / SARAH / LANHEP / UFO

MatrixElements

Parton showers
Hadronisation

Detector
Reconstruction

Simulated collisions• QCD environment
Parton showering★ Hadronisation★ Underlying event★

• Detector simulation

Simulation of the detector response★ Object reconstruction★

Analysis• Event analysis

Signal/background analysis★ LHC recasting★

New physics simulations − From Lagrangians to events and back

Benjamin Fuks - 01.03.2023 - 6

Connecting ideas to simulations…
[ Christensen, de Aquino, Degrande, Duhr, BF, Herquet, Maltoni & Schumann (EPJC`11) ]• Model building
Idea / Lagrangian

FEYNRULES, LANHEP, SARAHUFO• Hard scattering

Feynman diagram and amplitude generation★ Monte Carlo integration
CALCHEP, HERWIG++, MG5_AMC,★ Event generation
SHERPA, WHIZARD, …
★

FEYNRULES / SARAH / LANHEP / UFO

MatrixElements

Parton showers
Hadronisation

Detector
Reconstruction

Simulated collisions• QCD environment
Parton showering★ Hadronisation★ Underlying event★

• Detector simulation

Simulation of the detector response★ Object reconstruction★

Analysis• Event analysis

Signal/background analysis★ LHC recasting★

New physics simulations − From Lagrangians to events and backHERWIG, PYTHIA, SHERPA

DELPHESRIVET / MADANALYSIS 5 − SFS

RIVET / MADANALYSIS 5

Benjamin Fuks - 01.03.2023 - 6

Outline1.

A comprehensive approach for Monte Carlo simulations

2.

Implementing models into Monte Carlo event generators

3.

From events to Lagrangian: reinterpretation of the results of the LHC

4.

Summary

New physics simulations − From Lagrangians to events and back

Benjamin Fuks - 01.03.2023 - 7

The role of the Lagrangian
Implementation of a new physics model in an MC programme• De nition: particles, parameters and vertices (≣ Lagrangian)➙ translated in some programming language• Tedious, time-consuming, error prone• Beware of restrictions/conventionsfi

New physics simulations − From Lagrangians to events and back

Benjamin Fuks - 01.03.2023 - 8

The role of the Lagrangian
Implementation of a new physics model in an MC programme• De nition: particles, parameters and vertices (≣ Lagrangian)➙ translated in some programming language• Tedious, time-consuming, error prone• Beware of restrictions/conventions★ Highly redundant (each tool, each model)★ No-brainer tasks (from Feynman rules to codes)©Degrandefi

New physics simulations − From Lagrangians to events and back

Benjamin Fuks - 01.03.2023 - 8

The role of the Lagrangian
Implementation of a new physics model in an MC programme• De nition: particles, parameters and vertices (≣ Lagrangian)➙ translated in some programming language• Tedious, time-consuming, error prone• Beware of restrictions/conventions★ Highly redundant (each tool, each model)★ No-brainer tasks (from Feynman rules to codes)

Systematisation
Automation©Degrandefi

New physics simulations − From Lagrangians to events and back

©Degrande

Benjamin Fuks - 01.03.2023 - 8

Programmes connecting Lagrangians and HEP software

The FEYNRULES platform (since 2009)• Working environment: MATHEMATICA
Flexibility, symbolic manipulations, easy implementationof new methods, etc.
★ Many plugins (superspace, spectrum, decays, NLO, etc.)★

• Interfaces to many MC tools
Dedicated interfaces (CALCHEP, FEYNARTS)★ Generic interface: UFOs
(MG5_AMC, HERWIG, SHERPA, WHIZARD, …)★

• Very few limitations on models
Higher-dimensional operators supported★ Spins (up to 2); colour structures (1, 3, 6, 8)★

[ Christensen & Duhr (CPC ’09) ][ Alloul, Christensen, Degrande, Duhr & BF (CPC’14) ]New physics simulations − From Lagrangians to events and back

Benjamin Fuks - 01.03.2023 - 9

Programmes connecting Lagrangians and HEP software

The FEYNRULES platform (since 2009)LANHEP (since 1997)• Working environment: MATHEMATICA• Working environment: C• Initially restricted to CALCHEP/COMPHEP• Later interfaced to FEYNARTS/UFOs

Flexibility, symbolic manipulations, easy implementationof new methods, etc.
★ Many plugins (superspace, spectrum, decays, NLO, etc.)★

• Interfaces to many MC tools
Dedicated interfaces (CALCHEP, FEYNARTS)★ Generic interface: UFOs
(MG5_AMC, HERWIG, SHERPA, WHIZARD, …)★

• Very few limitations on models
Higher-dimensional operators supported★ Spins (up to 2); colour structures (1, 3, 6, 8)★

[ Christensen & Duhr (CPC ’09) ][ Alloul, Christensen, Degrande, Duhr & BF (CPC’14) ]New physics simulations − From Lagrangians to events and back[ Semenov (CPC’98); Semenov (CPC’16) ]The SARAH package (since 2010)• Working environment: MATHEMATICA• Spectrum generator, indirect constraints• Interfaced to many tools(CALCHEP, FEYNARTS, UFO, WHIZARD)[ Staub (CPC’10); Staub (CPC’14) ]Benjamin Fuks - 01.03.2023 - 9

Interfacing Lagrangians and MC tools
How to link a Lagrangian to a given MC tool?

• Model Feynman rules (vertices, particle content, etc.)• Removal of vertices not compliant with the tool

➙ Colour structures➙ Lorentz structures• Translation to a speci c format and programming languagefifi

New physics simulations − From Lagrangians to events and back➙ not ef cient➙ too many translators

Benjamin Fuks - 01.03.2023 - 10

Interfacing Lagrangians and MC tools
How to link a Lagrangian to a given MC tool?

• Model Feynman rules (vertices, particle content, etc.)• Removal of vertices not compliant with the tool

➙ Colour structures➙ Lorentz structures• Translation to a speci c format and programming language➙ not ef cient➙ too many translators

The UFO: one format to rule them all
Idea
LagrangianUFO

FEYNRULES(1)c̄He ⇥ † ! ⇤⇥ µ ⇤
Dµ
ē e
⇤2
⇤⇥
⇤
c̄`` ⇥+ 2 L̄ µ L L̄ µ L⇤⇤⇥⇤
c̄`H ⇥+ 2 ye †L̄e⇤⇤c̄uH ⇥ † ⇤⇥ †+ 2 yu
· Q̄u
⇤
+ ...

Chain oftools

Simulatedcollisions

Other
tools

Event
analysis

L=i<latexit sha1_base64="PKrc9ajc44Q/pskWD6riANRZkPY=">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</latexit>fifi

New physics simulations − From Lagrangians to events and back

Benjamin Fuks - 01.03.2023 - 10

The Universal FEYNRULES Output
The UFO in a nutshell[ Degrande, Duhr, BF, Grellscheid, Mattelaer, Reiter (CPC ’12) ][ Degrande, Duhr, BF, Hirschi, Mattelaer, Pagani, Shao et al. (in prep.) ]• UFO ≣ Universal FEYNRULES output ➙ Universal Feynman Output★

Universal as not tied to any speci c programme• Set of PYTHON les to be linked to any code
• A PYTHON model with full information©Degrande

Generic colour and Lorentz structures★ Up to software to enforce restrictions on acceptable colour/Lorentz structures★

• Allows for next-to-leading order calculationsfi

fi

New physics simulations − From Lagrangians to events and back

Benjamin Fuks - 01.03.2023 - 11

The Universal FEYNRULES Output[ Degrande, Duhr, BF, Grellscheid, Mattelaer, Reiter (CPC ’12) ][ Degrande, Duhr, BF, Hirschi, Mattelaer, Pagani, Shao et al. (in prep.) ]The UFO in a nutshell• UFO ≣ Universal FEYNRULES output ➙ Universal Feynman Output★

Universal as not tied to any speci c programme• Set of PYTHON les to be linked to any code
• A PYTHON model with full information©Degrande

Generic colour and Lorentz structures★ Up to software to enforce restrictions on acceptable colour/Lorentz structures★

• Allows for next-to-leading order calculations
Initially designed as the MG5aMC model format, UFOs now standard
FEYNRULESALOHACONTUR

MADGRAPH5_aMC@NLO

fifi

New physics simulations − From Lagrangians to events and back

SARAH
GOSAM
MADANALYSIS 5

LANHEPHERWIG ++SHERPAMADDM
WHIZARD

Benjamin Fuks - 01.03.2023 - 11

The UFO in practice
The UFO ≡ set of PYTHON les• Factorisation of the information in mandatory and optional les➙ particles➙ parameters➙ interactions➙ extra stuff (NLO, decays, propagators, functions, etc.)• Economical implementation of vertices and structures through recycling across the model
Particles

NLO

Interactions[ Arina, BF & Mantani (EPJC'20) ]Benjamin Fuks - 01.03.2023 - 12fi

fi

New physics simulations − From Lagrangians to events and backParameters

The UFO: particles & parameters
Particles ≡ instances of the particle class• Attributes: spin, colour representation, mass, width, etc.
• Antiparticles automatically derived

New physics simulations − From Lagrangians to events and back

Benjamin Fuks - 01.03.2023 - 13

The UFO: particles & parameters
Particles ≡ instances of the particle classParameters ≡ instances of the parameter class• Attributes: spin, colour representation, mass, width, etc.
• Antiparticles automatically derived• External parameters: Les Houches-like structure• PYTHON-compliant formula for the internal parameters

New physics simulations − From Lagrangians to events and back

Benjamin Fuks - 01.03.2023 - 13

The UFO: strategy for interactions
Decomposition in a spin x colour basis (coupling strengths ≡ coordinates)• Example: the quartic gluon vertex
igs2 f a1 a2 b f ba3 a4 (⌘ µ1 µ4 ⌘ µ2 µ3⌘ µ1 µ3 ⌘ µ2 µ4 )+ igs2 f a1 a3 b f ba2 a4 (⌘ µ1 µ4 ⌘ µ2 µ3⌘ µ1 µ2 ⌘ µ3 µ4 )+ igs2 f a1 a4 b f ba2 a3 (⌘ µ1 µ3 ⌘ µ2 µ4⌘ µ1 µ2 ⌘ µ3 µ4 )New physics simulations − From Lagrangians to events and back

Benjamin Fuks - 01.03.2023 - 14

The UFO: strategy for interactions
Decomposition in a spin x colour basis (coupling strengths ≡ coordinates)• Example: the quartic gluon vertex
igs2 f a1 a2 b f ba3 a4 (⌘ µ1 µ4 ⌘ µ2 µ3• UFO version
f a1 a2 b f ba3 a4 , f a1 a3 b f ba2 a4 , f a1 a4 b f ba2 a3
0 2
10 µµ µµigs
00
⌘ 1 4⌘ 2 3⇥ @ 0 igs2 0 A @ ⌘ µ1 µ4 ⌘ µ2 µ300 igs2⌘ µ1 µ3 ⌘ µ2 µ4⌘ µ1 µ3 ⌘ µ2 µ4 )+ igs2 f a1 a3 b f ba2 a4 (⌘ µ1 µ4 ⌘ µ2 µ3+ igs2 f a1 a4 b f ba2 a3 (⌘ µ1 µ3 ⌘ µ2 µ4⌘µ1 µ2 µ3 µ4⌘)⌘ µ1 µ2 ⌘ µ3 µ4 )µ1 µ3 µ2 µ4

1⌘⌘⌘ µ1 µ2 ⌘ µ3 µ4 A
⌘ µ1 µ2 ⌘ µ3 µ4

3 elements for the colour basis★ 3 elements for the spin (Lorentz structure) basis★ 9 coordinates (6 are zero, only 1 encoded)★

Information split across several lesfi

New physics simulations − From Lagrangians to events and back

Benjamin Fuks - 01.03.2023 - 14

UFOs @ NLO: generalities
NLO predictions in a nutshell• Three ingredients: the Born, virtual loop and real emission contributions
N LO =

Z

d4

nB

Born

New physics simulations − From Lagrangians to events and back

+

Z

d4

n

Z

loop

dd ` V

Virtuals: one extra power of
αs and divergent

+

Z

d4

n+1 R

Reals: one extra powerof αs and divergent

Benjamin Fuks - 01.03.2023 - 15

UFOs @ NLO: generalities
NLO predictions in a nutshell• Three ingredients: the Born, virtual loop and real emission contributions
N LO =

Z

d4

nB

Born

+

Z

d4

n

Z

loop

dd ` V+

Virtuals: one extra power of
αs and divergent

Z

d4

n+1 R

Reals: one extra powerof αs and divergent

Goal: automated predictions, for any process in any model
Extra information needed• Dimensional regularisation
UFO@NLO➙ Calculations in d = 4 − 2 dimensions➙ Divergences explicit (1/ 2, 1/ ) after reduction of tensor integral reduction• Numerical methods in 4 dimensions ➙ R1 and R2 terms• Renormalisation ➙ counterterms𝞮𝞮𝞮

New physics simulations − From Lagrangians to events and back[ Ossola, Papadopoulos, Pittau (NPB’07) ][ Ossola, Papadopoulos, Pittau (JHEP’08) ]Benjamin Fuks - 01.03.2023 - 15

UFOs @ NLO in practice
The reduction must be performed in a d-dimensional space
Z

k1

k2

kn

˜
N
(`,
`)
with `¯ = ` + `˜
dd `D̄0 D̄1 · · · D̄m 1
D-dim

4-dim

l + k1 = l + p1l

D0

D2 l + k1 + k2 + k3 = l + p2

Dm 1(-2 )-dim

k3

D1

k4

D3
l + k1 + . . . + k6 = l + p3

k5
k6

𝞮

New physics simulations − From Lagrangians to events and back

Benjamin Fuks - 01.03.2023 - 16

UFOs @ NLO in practice
The reduction must be performed in a d-dimensional space
Z

k1

k2

kn

˜
N
(`,
`)
with `¯ = ` + `˜
dd `D̄0 D̄1 · · · D̄m 1
D-dim

4-dim

l + k1 = l + p1l

D0

D2 l + k1 + k2 + k3 = l + p2

Dm 1(-2 )-dim

k3

D1

k4

D3
l + k1 + . . . + k6 = l + p3

R1 terms from denominators

k5
k6

_

• dD vs. 4D internal propagators (Di →Di)
• Computed on the y (a few non-zero extra integrals)fl𝞮New physics simulations − From Lagrangians to events and back

Benjamin Fuks - 01.03.2023 - 16

UFOs @ NLO in practice
The reduction must be performed in a d-dimensional space
Z

k1

k2

kn

˜
N
(`,
`)
with `¯ = ` + `˜
dd `D̄0 D̄1 · · · D̄m 1
D-dim

4-dim

l + k1 = l + p1l

D0

D2 l + k1 + k2 + k3 = l + p2

Dm 1(-2 )-dim

k3

D1

k4

D3
l + k1 + . . . + k6 = l + p3

R1 terms from denominators

k5
k6

_

• dD vs. 4D internal propagators (Di →Di)
• Computed on the y (a few non-zero extra integrals)

R2 terms from numerators2
˜
Process-dependent
contributions
proportional
to`•• Renormalisable theory➙ Extra diagrams with special Feynman rules (R2 Feynman rules)➙ Connected to the UV structure of the integrals (like counterterms)• Derivation of these extra Feynman rules➙ Finite number of R2’s from the bare Lagrangian
UFO @ NLO
➙ Calculated together with UV counterterms➙ The NLOCT package [ Degrande (CPC’15) ]fl

𝞮New physics simulations − From Lagrangians to events and back

Benjamin Fuks - 01.03.2023 - 16

NLO simulations with FEYNRULES & MG5_AMC[ Christensen, de Aquino, Degrande, Duhr, BF, Herquet, Maltoni & Schumann (EPJC`11) ]Idea / Lagrangian

FEYNRULES / UFO

Model building: from Lagrangian to tools• FEYNRULES ➙ UFO (@NLO)• PYTHON representation of the theory• Automation of one-loop calculations[ Alloul, Christensen, Degrande, Duhr & BF (CPC’14) ][ Degrande, Duhr, BF, Mattelaer & Reither (CPC’12) ][ Degrande (CPC’15) ]Hard-scattering process with MG5_aMC
MatrixElements• Feynman diagrams, matrix elements• Perturbative series (LO/NLO)• Automation from the UFO information[ Alwall et al. (JHEP’14) ][ Frederix, Frixione, Hirschi, Pagani, Shao & Zaro (JHEP`18) ][ Frixione, BF, Hirschi, Mawatari, Shao, Sunder & Zaro (JHEP`19) ]Collider observables

Phenomenology

Collider phenomenology• Matching with parton showers• Hadronisation models• Detector simulation
See all other lectures

New physics simulations − From Lagrangians to events and back

Benjamin Fuks - 01.03.2023 - 17

Outline1.

A comprehensive approach for Monte Carlo simulations

2.

Implementing models into Monte Carlo event generators

3. From events to Lagrangian: reinterpretation of the results of the LHC

4.

Summary

New physics simulations − From Lagrangians to events and back

Benjamin Fuks - 01.03.2023 - 18

From Lagrangians to events
New physics simulations standard today• 20 − 25 years of developments• Simulations at LO/NLO easily achieved
Idea
Lagrangian

Chain oftools

Simulatedcollisions

Other
tools

Event
analysisAny model Easy validation

Let’s reverse the chain…

New physics simulations − From Lagrangians to events and back

Benjamin Fuks - 01.03.2023 - 19

New physics results at the LHC
LHC ≡ discovery machine• Many ATLAS and CMS searches for new physics• Interpretation within popular frameworks and simpli ed models

New physics simulations − From Lagrangians to events and backfi

Benjamin Fuks - 01.03.2023 - 20

New physics results at the LHC
LHC ≡ discovery machine• Many ATLAS and CMS searches for new physics• Interpretation within popular frameworks and simpli ed models

Need for reinterpretations in all kinds of models

New physics simulations − From Lagrangians to events and backfi

Benjamin Fuks - 01.03.2023 - 20

Simpli ed Model Spectra (SMS)The SMS-based reinterpretation framework• Decomposition of all signatures of a theory into SMS signatures• Fiducial cross sections on the basis of public ef ciency maps
• Comparisons to published upper bounds
Main features[ Kraml et al. (EPJC’14) ]Benjamin Fuks - 01.03.2023 - 21fi

fi

New physics simulations − From Lagrangians to events and back

Simpli ed Model Spectra (SMS)The SMS-based reinterpretation framework• Decomposition of all signatures of a theory into SMS signatures• Fiducial cross sections on the basis of public ef ciency maps
• Comparisons to published upper bounds
Main features[ Kraml et al. (EPJC’14) ]• Rather fast
• Often conservative

Different kinematics★ Asymmetric decays★

Benjamin Fuks - 01.03.2023 - 21fi

fi

New physics simulations − From Lagrangians to events and back

Simpli ed Model Spectra (SMS)The SMS-based reinterpretation framework• Decomposition of all signatures of a theory into SMS signatures• Fiducial cross sections on the basis of public ef ciency maps
• Comparisons to published upper bounds
Main features[ Kraml et al. (EPJC’14) ]• Rather fast
• Often conservative

Different kinematics★ Asymmetric decays★

• A generic program: SmodelS

O(100) available analyses★ Prompt and LLP decays[ Kraml et al. (EPJC’14) ]★ Available from GITHUB[ Kraml et al. (LHEP’20) ]★

• Dark photons: DARKCAST★

[ Ilten et al. (JHEP’18) ]Benjamin Fuks - 01.03.2023 - 21fi

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New physics simulations − From Lagrangians to events and back

Available from GITLABSMS reinterpretation tools - examples[Goodsell et al. (SciPost’20) ]DGMSSM at the LHC• Exploring SUSY with Dirac gauginos• Models not considered by ATLAS/CMS• Left: points excluded by SMODELS (with r ≥ 1)
• Right: comparison with full recasts(from MADANALYSIS 5)➙ SMS approach fair enough➙ Far from full recasts• SMS approach much fasterNew physics simulations − From Lagrangians to events and back

• Usually provides fair estimates

Benjamin Fuks - 01.03.2023 - 22

SMS reinterpretation tools - examples[Goodsell et al. (SciPost’20) ]DGMSSM at the LHC• Exploring SUSY with Dirac gauginos• Models not considered by ATLAS/CMS• Left: points excluded by SMODELS (with r ≥ 1)
• Right: comparison with full recasts(from MADANALYSIS 5)➙ SMS approach fair enough➙ Far from full recasts• SMS approach much faster[ Edelhäuser, Krämer, Sonneveld (JHEP’15) ]SUSY vs extra dimensions• Using SUSY searches to constrain KK excitations➙ Blue: SMS approach➙ Red: full recast• Ef ciencies depend on particle spins➙ SMS approach often fair enough➙ SMS approach often too aggressivefi

New physics simulations − From Lagrangians to events and back

• Usually provides fair estimates

Benjamin Fuks - 01.03.2023 - 22

Beyond the SMS approach
SMS often not suf cient to study all interesting new physics realisations• More accurate detector simulations➙ mimicking ATLAS / CMS• New frameworks for LHC re-interpretations➙ Easy (re-)implementations of searches➙ Test of signals fully automated
Tuned detector simulationfi

New physics simulations − From Lagrangians to events and back

Benjamin Fuks - 01.03.2023 - 23

Beyond the SMS approach
SMS often not suf cient to study all interesting new physics realisations• More accurate detector simulations➙ mimicking ATLAS / CMS• New frameworks for LHC re-interpretations➙ Easy (re-)implementations of searches➙ Test of signals fully automated

The detector is the key• Close to a real detector (slower)➙ from particles to tracks/hits➙ resolutions, ef ciencies, etc.
➙ à la Delphes 3 [ de Favereau et al. (JHEP`14) ]• Based on transfer functions (faster)➙ From MC particles➙ Resolutions, ef ciencies, …
➙ à la RIVET, MADANALYSIS 5 − SFS

Tuned detector simulation[ Araz, BF & Polykratis (EPJC`21) ][ Bierlich et al. (SciPost`20) ]• Unfolding➙ No need for a detector

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New physics simulations − From Lagrangians to events and back

Benjamin Fuks - 01.03.2023 - 23

Detector based on (customised) DELPHES 3• CHECKMATE [O(50) analyses, from GITHUB]• MADANALYSIS 5 [ O(50) analyses, from GITHUB and the MA5 DATAVERSE][ Derks et al. (CPC`17) ][ Dumont, BF, Kraml et al. (EPJC`15); Conte & BF (IJMPA`19) ]Constraining t-channel dark matter with jets + MET (in MADANALYSIS 5)𝟁

New physics simulations − From Lagrangians to events and backPreliminary• SM ⊕ coloured fermion ( ) ⊕ scalar DM (S) ⊕ coupling to uR• Signal modelling crucial: XX,YY and XY production @ NLO[ Arina, BF, Heisig, Kramer, Mantani, Panizzi & Salko (to appear) ]Examples from public programmes

Benjamin Fuks - 01.03.2023 - 24

Detector based on (customised) DELPHES 3• CHECKMATE [O(50) analyses, from GITHUB]• MADANALYSIS 5 [ O(50) analyses, from GITHUB and the MA5 DATAVERSE][ Derks et al. (CPC`17) ][ Dumont, BF, Kraml et al. (EPJC`15); Conte & BF (IJMPA`19) ]Constraining t-channel dark matter with jets + MET (in MADANALYSIS 5)[ Athron et al. (EPJC`19) ]Preliminary• SM ⊕ coloured fermion ( ) ⊕ scalar DM (S) ⊕ coupling to uR• Signal modelling crucial: XX,YY and XY production @ NLO[ Arina, BF, Heisig, Kramer, Mantani, Panizzi & Salko (to appear) ]Examples from public programmes

Based on transfer functions• COLLIDERBIT [O(40) analyses, from HEPFORGE]• MADANALYSIS 5 - SFS [O(10) analyses, from GITHUB and the MA5-DATAVERSE]• RIVET [O(30) analyses, from HEPFORGE][ Balász et al. (EPJC`17) ] [Araz, BF & Polykratis (EPJC`21); Araz, BF, Goodsell & Utsch (EPJC`22) ][ Buckley et al. (2010); Bierlich et al. (SciPost`20) ]Constraining ewkinos with recursive Jigsaw (in COLLIDERBIT)• Validation ≡ closure test𝟁

New physics simulations − From Lagrangians to events and back

Benjamin Fuks - 01.03.2023 - 24

Implementing a new recast
Picking up an experimental publication• Reading• Understanding✅ Relatively easy

Writing the analysis code in the tool internal language

New physics simulations − From Lagrangians to events and back

Benjamin Fuks - 01.03.2023 - 25

Implementing a new recast
A 2012 TH-wishlist for high-quality recasts (1/2)
Picking up an experimental publication• Reading• Understanding✅ Relatively easy

Writing the analysis code in the tool internal language• Clear description of cuts and their sequence• Ef ciencies (e±, ±, jets, h, b-tagging, etc.)➙ Including pT/ dependence• Ef ciencies for triggers, event cleaning, etc.

➙ Effects not manageable in fast simulations• Special variable de nitions (razor, aMT2, etc.)➙ Snippets of code

[ Les Houches Recommendations (EPJC’12) ]

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New physics simulations − From Lagrangians to events and back

Benjamin Fuks - 01.03.2023 - 25

Implementing a new recast
A 2012 TH-wishlist for high-quality recasts (1/2)
Picking up an experimental publication• Reading• Understanding✅ Relatively easy

Writing the analysis code in the tool internal language• Clear description of cuts and their sequence• Ef ciencies (e±, ±, jets, h, b-tagging, etc.)➙ Including pT/ dependence• Ef ciencies for triggers, event cleaning, etc.

➙ Effects not manageable in fast simulations• Special variable de nitions (razor, aMT2, etc.)➙ Snippets of code

Accurate information for proper validation• Ef ciencies (trigger, e±, ±, b-tagging, JES, etc.)➙ including pT/ dependence• Detailed cut ows for well-de ned benchmarks➙ Region per region information➙ Exact de nition of benchmarks (spectra)➙ Event generation information (cards, tunes)• Digitised histograms (e.g. on HEPDATA)⚠ Essential❌

Often dif cult!

[ Les Houches Recommendations (EPJC’12) ]

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New physics simulations − From Lagrangians to events and back

Benjamin Fuks - 01.03.2023 - 25

Implementing a new recast
A 2012 TH-wishlist for high-quality recasts (1/2)
Picking up an experimental publication• Reading• Understanding✅ Relatively easy

Writing the analysis code in the tool internal language• Clear description of cuts and their sequence• Ef ciencies (e±, ±, jets, h, b-tagging, etc.)➙ Including pT/ dependence• Ef ciencies for triggers, event cleaning, etc.

➙ Effects not manageable in fast simulations• Special variable de nitions (razor, aMT2, etc.)➙ Snippets of code

A 2012 TH-wishlist for high-quality recasts (2/2)

Accurate information for proper validation• Efciencies (trigger, e±,• Benchmark scenarios±, b-tagging, JES, etc.)➙ including pT/ dependence• Detailed cut ows for well-de ned benchmarks➙ Region per region information➙ Exact de nition of benchmarks (spectra)➙ Event generation information (cards, tunes)• Digitised histograms (e.g. on HEPDATA)⚠ Essential❌

Often dif cult!

➙ Spectra / decay tables (SLHA-form)➙ Several scenarios• Monte Carlo con guration➙ Cards, tunes, matching information, etc.
• Detailed cut ows (with correct cut ordering)➙ Including (pre)selection steps (more is better)• Kinematical distributions at different cuts
➙ Extra cross-checks[ Les Houches Recommendations (EPJC’12) ]

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New physics simulations − From Lagrangians to events and back

Benjamin Fuks - 01.03.2023 - 25

10 years later…
[ Agin with MADANALYSIS 5 ]Much better material• Publications much clearer• HEPDATA widely used
• Improved communication between the EXP/TH communities• Sometimes works amazingly well: e.g. ATLAS multijet+MET• Still improvable: e.g. ATLAS dE/dx [HSCP with large ionisation][ ATLAS (2022) ]New physics simulations − From Lagrangians to events and back

Benjamin Fuks - 01.03.2023 - 26

10 years later…
[ Agin with MADANALYSIS 5 ]Much better material• Publications much clearer• HEPDATA widely used
• Improved communication between the EXP/TH communities• Sometimes works amazingly well: e.g. ATLAS multijet+MET• Still improvable: e.g. ATLAS dE/dx [HSCP with large ionisation]
A 2020 TH-wishlist for high-quality recasts➙ Should be provided as tables / functional forms➙ Should be broken down in sub-ef ciencies (trigger, etc.)• Ef ciency maps: necessary for SMS-based recasting• Monte Carlo: still very minimal➙ SLHA les, MG5_aMC cards, PYTHIA cards, etc.
➙ Crucial for the validation (cf. MC bias)[ ATLAS (2022) ]• Background estimates: usually provided (not systematic)• Ef ciencies• Cut- ows for given benchmarks➙ not systematic (sequence, details, all SRs)
[ The Reinterpretation Forum (SciPost`20) ]

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New physics simulations − From Lagrangians to events and back

Benjamin Fuks - 01.03.2023 - 26

Strength in numbers: combination of searches• Recast exclusions from the best region of an analysis• Often off relative to CMS/ATLAS ➙ correlations rarely negligible

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New physics simulations − From Lagrangians to events and back

Benjamin Fuks - 01.03.2023 - 27

Strength in numbers: combination of searches• Recast exclusions from the best region of an analysis• Often off relative to CMS/ATLAS ➙ correlations rarely negligible➙ Derivation of an approximate correlation matrix• Optimal combinations among them (tests over 100s of regions)➙ Better reinterpretation power

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New physics simulations − From Lagrangians to events and back

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Benjamin Fuks - 01.03.2023 - 27

Outline1.

A comprehensive approach for Monte Carlo simulations

2.

Implementing models into Monte Carlo event generators

3. From events to Lagrangian: reinterpretation of the results of the LHC

4.

Summary

New physics simulations − From Lagrangians to events and back

Benjamin Fuks - 01.03.2023 - 28

Summary
The quest for new physics is on-going• MC tools for background/signal modelling• Automated methods for model implementation➙ Facilitates new physics simulations at (N)LO
Tutorial: Give FEYNRULES a try!

New physics simulations − From Lagrangians to events and back

Idea
Lagrangian

Chain oftools

Simulatedcollisions

Other
tools

Event
analysisAny model Easy validation

Benjamin Fuks - 01.03.2023 - 29

Summary
The quest for new physics is on-going• MC tools for background/signal modelling• Automated methods for model implementation

Idea
Lagrangian

Chain oftools

➙ Facilitates new physics simulations at (N)LO
Tutorial: Give FEYNRULES a try!

Simulatedcollisions

Other
tools

Event
analysisAny model Easy validation

The LHC legacy• Reinterpretation of the LHC results in any theoretical context crucial➙ Two complementary approaches: simpli ed models and detector simulation• Exciting on-going developments: combining & correlating

Tuned detector
simulation

Tutorial: Give MADANALYSIS 5 a try!

fi

New physics simulations − From Lagrangians to events and back

Benjamin Fuks - 01.03.2023 - 29

Summary
The quest for new physics is on-going• MC tools for background/signal modelling• Automated methods for model implementation

Idea
Lagrangian

Chain oftools

➙ Facilitates new physics simulations at (N)LO
Tutorial: Give FEYNRULES a try!

Simulatedcollisions

Other
tools

Event
analysisAny model Easy validation

The LHC legacy• Reinterpretation of the LHC results in any theoretical context crucial➙ Two complementary approaches: simpli ed models and detector simulation• Exciting on-going developments: combining & correlating

Tuned detector
simulation

Tutorial: Give MADANALYSIS 5 a try!

Final last words• Reproducibility ≡ ability of an entire experiment to be reproduced(possibly by an independent theoretical study)• Need for both the TH and EXP communities to move together!

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New physics simulations − From Lagrangians to events and back

Benjamin Fuks - 01.03.2023 - 29