Area 2 : Predictions and tools C. Degrande, G. Petrucciani

Institut de recherche en mathématique et physiqueCentre de Cosmologie, Physique des Particules et Phénoménologie

C. Degrande

• Available predictions and tools

• Reweighting

• Uncertainties

• EFT validity

• Unstable particles

Plan

2

Available predictions and tools

C. Degrande

General : •Which basis, which operators are included? •SM input scheme

•𝚲 order, form factors

•Which processes? which observable? •Compare/validate models at LO (E.g. 1906.12310)

Analytical : list the results published (so far?) (~1000 SMEFT papers) •Dynamical resource (updated when new results appear)

Numerical: •List of models •Which generators for EFT? Limitation (Lorentz structures,...)? •Compare generators at LO (E.g. Madgraph vs Sherpa)

At LO

4

C. Degrande

• What is available? 

• Any analytic results? 

• Numerical (SMEFT@NLO 2008.11743, other process specific VBFNLO)

• Which running/scheme of the coefficients?

• Comparison between generators and published results

• Comparison between generators : Madgraph5aMC@NLO vs recola? vs sherpa? 

• EW corrections? Match to PS?


At NLO

5

https://arxiv.org/abs/2008.11743https://arxiv.org/abs/2008.11743

Reweighting

C. Degrande

• Goal: Avoid expensive generation & detector simulation

• Why: many different EFT points/parameters

• How: compute predictions of space points from the same set of generated events, using weights from ratio of matrix elements

• helpful if generating events for the full 2 → N process is not feasible?

Reweighting

7

C. Degrande

• Coupling to the generation :

• “weights can be computed only during generation”

• OR “weights can be computed for any LHE event irrespectively of generator”

• Depends on implementation,

• feasible for run 2 analysis

• strategy for run 3 MC generation

• Review approaches & tools: accuracy (NLO, spin correlations, …), validation

Reweighting

8

Uncertainties

C. Degrande

• On the SM predictions :

• Are EFT effects large where SM corrections are also large (large energy spread)?

• On the EFT predictions:

• Higher order in the SM couplings

• Higher order in 𝚲

• Scale (running) and PDF uncertainties (PDF at LO/NLO/NNLO)

• EFT contribution to background

• Scaling the EFT contribution as the SM?

Uncertainties

10

EFT validity

C. Degrande

• Only c/𝚲2 is measured but we need Eexp

C. Degrande

EFT & scales

Unitarity bound

SM

NP onlySM+NP

1/⇤0

PerturbativityUnitarity

1/⇤2

We measure , what is ?Ci⇤2

⇤

⇠ ⇤

> ⇤ E

13

NP only 1/Λ4

C. Degrande

EFT & scales

Unitarity bound

SM

NP onlySM+NP

1/⇤0

PerturbativityUnitarity

1/⇤2

+Form Factor

We measure , what is ?Ci⇤2

⇤

⇠ ⇤

> ⇤ E

13

NP only 1/Λ4

C. Degrande

EFT & scales

Unitarity bound

SM

NP onlySM+NP

1/⇤0

PerturbativityUnitarity

1/⇤2

+Form Factor

Precise : EFT (model ind.) We measure , what is ?

Ci⇤2

⇤

⇠ ⇤

> ⇤ E

13

NP only 1/Λ4

C. Degrande

EFT & scales

Unitarity bound

SM

NP onlySM+NP

1/⇤0

PerturbativityUnitarity

1/⇤2

+Form Factor

Precise : EFT (model ind.)

SM±>100% Assume SM +dim6 only

We measure , what is ?Ci⇤2

⇤

⇠ ⇤

> ⇤ E

13

NP only 1/Λ4

C. Degrande

EFT & scales

Unitarity bound

SM

NP onlySM+NP

1/⇤0

PerturbativityUnitarity

1/⇤2

+Form Factor

Precise : EFT (model ind.)

SM±>100% Assume SM +dim6 only

Unitarity allowed

We measure , what is ?Ci⇤2

⇤

⇠ ⇤

> ⇤ E

13

NP only 1/Λ4

C. Degrande

• Only c/𝚲2 is measured but we need Eexp

Unstable particles

C. Degrande

• EFT : • in production (lower number of final state, faster

(NLO))

• decay (as top polarisation)

• or both (ideal theoretically, many approximation from prod x Br to full ME)

• Width depends on 𝚲, how to truncate?

• Which scheme (Complex mass scheme and basis dependence)

Unstable particles (W,Z,t,H)

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