Abstract

We present a complete list of the dimension 8 operator basis in the standard model effective field theory using group theoretic techniques in a systematic and automated way. We adopt a new form of operators in terms of the irreducible representations of the Lorentz group, and identify the Lorentz structures as states in a $SU(N)$ group. In this way, redundancy from equations of motion is absent and that from integration-by-part is treated using the fact that the independent Lorentz basis forms an invariant subspace of the $SU(N)$ group. We also decompose operators into the ones with definite permutation symmetries among flavor indices to deal with subtlety from repeated fields. For the first time, we provide the explicit form of independent flavor-specified operators in a systematic way. Our algorithm can be easily applied to higher dimensional standard model effective field theory and other effective field theories, making these studies more approachable.

Highlights

  • The standard model (SM) of particle physics is a great triumph of modern physics

  • We provided the full result of the independent dimension-eight operator basis in the standard model effective field theory

  • What is more important is that the form of the operators we provide here has definite symmetry over the flavor indices, making it possible to identify independent flavor-specified operators

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Summary

INTRODUCTION

The standard model (SM) of particle physics is a great triumph of modern physics. It has successfully explained almost all experimental results and predicted a wide variety of phenomena with unprecedented accuracy. This task is highly nontrivial because different structured operators may be related by the equation of motion (EOM), integration by parts (IBP), and Fierz identities These redundancies could be avoided by imposing the EOMs and IBPs explicitly, the independent dimension-six operators in the Warsaw basis [3] were constructed based on this principle, and the complete renormalization group equations are written in Refs. Reference [16] generates an overcomplete list of operators at first, and reduces it to an independent basis by putting all the redundant relations into a matrix, which has been applied [24] to write down the partial list of the dimensioneight operators involving only the bosonic fields Another difficulty is how to obtain independent flavor structures when repeated fields are present. In Appendix B, we introduce some basics of symmetric groups Sm and a few group theory tools we used in the paper, including the basis symmetrizer bλ and the projection operator involved in the inner product decomposition

SM fields
Invariants at different levels
Motivation and mathematical preparation
Why permutation symmetry
Group algebra and left ideal
Lorentz basis
Lorentz invariance
Lorentz structures as SUðNÞ states
Permutation
Gauge basis
Flavor basis
Lμν fð2εjk εlm1
Preview of the result
Classes involving bosons only
ÞðW J J ÞðW I
No gauge boson involved
One gauge boson involved Class Fψ2φ3
D HÞ ð4:38Þ
G AμνðuC
Two gauge boson involved
Classes involving four fermions
Two scalars involved
Operators involving only quarks
Operators involving two leptons and two quarks
One derivative involved
Two derivatives involved
One gauge boson involved Class Fψ4: There are two subclasses in this class
CONCLUSION
G BνμÞðQpaiσλ ðλCÞab
Convention in permutation operation
Projection operator and CGCs
Full Text
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