Standard Model Effective Field Theory (SMEFT) sim

Authors

Ilaria Bravio, Yun Jiang and Micheal Trott

ilaria.brivio@nbi.ku.dk, yunjiang@nbi.ku.dk, michael.trott@cern.ch

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

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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 is to provide a complete tool for the analysis of the tree level interference terms between the L₆ dependent amplitude and the SM amplitudes in a measured process. In this spirit, we stress that this package is neither to be employed for the extraction of accurate SM predictions nor equipped for NLO calculations in MadGraph5_aMC@NLO.

The models are built upon the default SM implementation in FeynRules, from which they inherit the SM fields, parameters and Lagrangian definitions. The original file has been extended and modified to include the complete set of L₆ baryon number conserving operators of the Warsaw basis. The loop-induced effective couplings of SM Higgs to gg, γγ and Zγ have also been included. At this stage, the ghost Lagrangian has been left in its SM form. The entire Wilson coefficient parameter space of the L₆ SMEFT and the automatic inclusion of the shifts due to the choice of an input parameters set are implemented.

Two independent sets are supplied in the SMEFTsim package. Each set contains a single master code and a number of subroutines, along with several restriction files. The model file can be loaded in FeynRules using the notebook program, with the product of the UFOs. Model files and pre-exported UFO files to be interfaced with MadGraph5_aMC@NLO can be downloaded on this page.

Each model set constructs three different versions of the SMEFT based on the flavor symmetry assumption adopted:

• a fully flavour general SMEFT
• a U(3)⁵ − SMEFT with non-SM complex phases
• Minimal flavor violation (MFV) SMEFT

In each model two input parameter schemes of choosing external parameters are employed:

• α scheme: {α_em, m_Z , G_f}
• m_W scheme: {m_W, m_Z , G_f}

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

Change log

v1.0 (17.09.2017) The first version released

References

• I. Bravio, Y. Jiang and M. Trott, The SMEFTsim package, theory and tools, ​arXiv:1709.XXXX

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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.

• This archive contains all the model files. Should be expanded in the FR model directory.
• Example of a Mathematica® notebook loading the model

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UFO generated files

	Set A		Set B
	α scheme	mW scheme	α scheme	mW scheme
Flavor general SMEFT
MFV SMEFT
U(3)5 SMEFT