Version 36 (modified by IlariaBrivio, 3 years ago) (diff)


Standard Model Effective Field Theory -- The SMEFTsim package


Ilaria Brivio, Yun Jiang and Micheal Trott,,

NBIA and Discovery Center, Niels Bohr Institute, University of Copenhagen

The model description

The SMEFT is constructed out of a series of SU(3)C × SU(2)L × U(1)Y invariant (local and analytic) higher dimensional operators L6, L7, ... built out of the SM fields.
The SMEFTsim package provides a complete implementation of the dimension-6 Lagrangian adopting the Warsaw basis arXiv:1008.4884

The SM Lagrangian is extended with the inclusion of the complete set of baryon-number-conserving operators of the Warsaw basis and of the SM loop-induced Higgs couplings to gg, γγ and Zγ.
Importantly, field rotations required to have canonically normalized kinetic terms and parameter redefinitions following from the choice of an input parameters set are automatically applied in the Lagrangian.

The SMEFTsim package provides implementations for 3 different flavor assumptions and 2 input scheme choices, for a total of 6 different models.

The flavor assumptions adopted are (see arXiv:1709.xxxxx for a detailed description)

  • The flavour general case
  • The U(3)5 flavor symmetric case, with possible non-SM CP-violating phases
  • A linear Minimal flavor violation (MFV) ansatz, in which non-SM CP-violating effects are neglected, but flavor-violation spurion insertions are allowed in quark currents

For each model it is possible to choose between two input parameters sets for the electroweak sector, namely:

  • α scheme: {αem, mZ , Gf}
  • mW scheme: {mW, mZ , Gf}

Two independent models sets (A and B) are supplied. Each set contains a main file, a number of subroutines and restriction files. The two sets differ in the structure and in the technical implementation of L6, but they produce consistent results. The use of both sets is recommended for debugging and validation of the numerical results.
Pre-exported UFO files to be interfaced with MadGraph5_aMC@NLO can also be downloaded from this page (see Table below).

We appreciate if you could report us any inconsistency or bugs.

Usage recommendations

The SMEFTsim package is designed to enable numerical studies of the LO interference of the SMEFT with the SM, while neglecting NLO corrections. In this spirit, it has not been optimized for loop calculations in the SM or in the SMEFT. In particular:

  • the Lagrangian assumes unitary gauge. Using it in Rxi or Feynman gauge may lead to inconsistent results, as the ghost Lagrangian have not been modified to account for L6 corrections.
  • the UFO files are not suitable for NLO evaluation in MadGraph5_aMC@NLO

Change log

v1.0 (17.09.2017) The first version released


Model Set A

Model Set B

In the master code two flags: Scheme and Flavor are established, which are used to identify the input scheme and flavor symmetry being adopted in loading the model.

(left with putting arXiv number in the main code *)

Pre-exported UFO files (include restriction cards)

Set A Set B
α scheme mW scheme α scheme mW scheme
Flavor general SMEFT SMEFTsim_A_general_alphaScheme_UFO.tar.gz SMEFTsim_A_general_MwScheme_UFO.tar.gz
MFV SMEFT SMEFTsim_A_MFV_alphaScheme_UFO.tar.gz SMEFTsim_A_MFV_MwScheme_UFO.tar.gz
U(3)5 SMEFT SMEFTsim_A_U35_alphaScheme_UFO.tar.gz SMEFTsim_A_U35_MwScheme_UFO.tar.gz

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