Eur. Phys. J. Plus (2017) 132: 16
https://doi.org/10.1140/epjp/i2017-11291-5

Regular Article

Field reparametrization in SMEFT

¹ Dipartimento di Fisica Teorica, Università di Torino, Torino, Italy
² INFN, Sezione di Torino, Torino, Italy

^* e-mail: giampiero@to.infn.it

Received: 2 November 2016
Accepted: 9 December 2016
Published online: 17 January 2017

Abstract

Debate topic for effective field theory (EFT) is the choice of a “basis” for operators. Clearly all bases are equivalent as long as they are a “basis”, containing a minimal set of operators after the use of equations of motion and respecting the gauge invariance. From a more formal point of view a basis is characterized by its closure with respect to renormalization. Equivalence of bases should always be understood as a statement for the S-matrix and not for the Lagrangian, as dictated by the equivalence theorem. Any phenomenological approach that misses one of these ingredients is still acceptable for a preliminar analysis, as long as it does not pretend to be an EFT. Here we revisit the equivalence theorem and its consequences for EFT when two sets of higher-dimensional operators are connected by a set of non-linear, non-invariant, field reparametrizations.