Possible treatment of the Ghost states in the Lee-Wick Standard Model

TL;DR

This paper proposes a method to address ghost states in the Lee-Wick Standard Model by constructing a positive definite metric operator, resulting in a Hermitian Hamiltonian without ghost states, thus improving the model's physical viability.

Contribution

It introduces an auxiliary field approach and calculates a metric operator that renders the Hamiltonian Hermitian and ghost-free in Lee-Wick scalar theories.

Findings

Derived a closed-form metric operator for the scalar Lee-Wick model.

Showed the Hamiltonian becomes Hermitian with the new inner product.

Established a relation between Higgs masses, M > 2m.

Abstract

Very recently, the Lee-Wick standard model has been introduced as a non-SUSY extension of the Standard model which solves the Hierarchy problem. In this model, each field kinetic term attains a higher derivative term. Like any Lee-Wick theory, this model suffers from existence of Ghost states. In this work, we consider a prototype scalar field theory with its kinetic term has a higher derivative term, which mimics the scalar sector in the Lee-Wick Standard model. We introduced an imaginary auxiliary field to have an equivalent non-Hermitian two-field scalar field theory. We were able to calculate the positive definite metric operator $\eta$ in quantum mechanical and quantum field versions of the theory in a closed form. While the Hamiltonian is non-Hermitian in a Hilbert space with the Dirac sense inner product, it is Hermitian in a Hilbert space endowed by the inner product $<n|\eta|m>$ as well as having a correct-sign propagator (no Lee-Wick fields). Besides, the obtained metric operator also diagonalizes the Hamiltonian in the two fields (no mixing). Moreover, the Hermiticity of $\eta$ constrained the two Higgs masses to be related as $M>2m$, which has been obtained in another work using a very different regime and thus supports our calculation. Also, an equivalent Hermitian (in the Dirac sense) Hamiltonian is obtained which has no Ghost states at all, which is a forward step to make the Lee-Wick theories more popular among the Physicists.